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This study reports and discusses new radiometric ages, petrographical and volcanological observations and whole rock geochemical data of the rocks of the Rudnik Mts. volcano-intrusive complex. The complex hosts a Pb-Zn-Ag deposit and belongs to the Serbo-Macedonian metallogenetic belt. Two distinct igneous events are distignuished. The first occurred >30 Ma and was mainly characterized by extrusive and shallow intrusive dacites and andesites and was unrelated to mineralization. The second igneous event occurred <23 Ma and was highly heterogeneous in terms of volcanic products and petrographic varieties, but with predominance of quartzlatites. The dacite-andesites (first event) and the quartzlatites (second event) are geochemically similar and display a calc-alkaline affinity and highly incompatible element enriched patterns on spider diagrams, but the younger quartzlatites are richer in K2O, Rb and Ba and poorer in Sr. This is taken as evidence that mixing between an ultrapotassic lamprophyre/lamproite magma and an acid calc-alkaline (dacite-like) magma was essential petrogenetic processes during the second event. The proposed simplified volcanological model suggests that this mixing was responsible for triggering strongly explosive volcanic activity as well as for providing conditions for active hydrothermal and mineralization processes. The observed link between a specific magmatic phase and ore deposit formation can be a general phennomenon in the Balkans, and must be addressed by further and more advanced studies.
Number concentrations of total and non-volatile aerosol particles with size diameters >0.01 µm as well as particle size distributions (0.4–23 µm diameter) were measured in situ in the Arctic lower stratosphere (10–20.5 km altitude). The measurements were obtained during the campaigns European Polar Stratospheric Cloud and Lee Wave Experiment (EUPLEX) and Envisat-Arctic-Validation (EAV). The campaigns were based in Kiruna, Sweden, and took place from January to March 2003. Measurements were conducted onboard the Russian high-altitude research aircraft Geophysica using the low-pressure Condensation Nucleus Counter COPAS (COndensation PArticle Counter System) and a modified FSSP 300 (Forward Scattering Spectrometer Probe). Around 18–20 km altitude typical total particle number concentrations nt range at 10–20 cm−3 (ambient conditions). Correlations with the trace gases nitrous oxide (N2O) and trichlorofluoromethane (CFC-11) are discussed. Inside the polar vortex the total number of particles >0.01 µm increases with potential temperature while N2O is decreasing which indicates a source of particles in the above polar stratosphere or mesosphere. A separate channel of the COPAS instrument measures the fraction of aerosol particles non-volatile at 250°C. Inside the polar vortex a much higher fraction of particles contained non-volatile residues than outside the vortex (~24% outside vortex). This is most likely due to a strongly increased fraction of meteoritic material in the particles which is transported downward from the mesosphere inside the polar vortex. The high fraction of non-volatile residual particles gives therefore experimental evidence for downward transport of mesospheric air inside the polar vortex. It is also shown that the fraction of non-volatile residual particles serves directly as a suitable experimental vortex tracer. Nanometer-sized meteoritic smoke particles may also serve as nuclei for the condensation of gaseous sulfuric acid and water in the polar vortex and these additional particles may be responsible for the increase in the observed particle concentration at low N2O. The number concentrations of particles >0.4 µm measured with the FSSP decrease markedly inside the polar vortex with increasing potential temperature, also a consequence of subsidence of air from higher altitudes inside the vortex. Another focus of the analysis was put on the particle measurements in the lowermost stratosphere. For the total particle density relatively high number concentrations of several hundred particles per cm3 at altitudes below ~14 km were observed in several flights. To investigate the origin of these high number concentrations we conducted air mass trajectory calculations and compared the particle measurements with other trace gas observations. The high number concentrations of total particles in the lowermost stratosphere are probably caused by transport of originally tropospheric air from lower latitudes and are potentially influenced by recent particle nucleation.
Number concentrations of total and non-volatile aerosol particles with size diameters >0.01 μm as well as particle size distributions (0.4–23 μm diameter) were measured in situ in the Arctic lower stratosphere (10–20.5 km altitude). The measurements were obtained during the campaigns European Polar Stratospheric Cloud and Lee Wave Experiment (EUPLEX) and Envisat-Arctic-Validation (EAV). The campaigns were based in Kiruna, Sweden, and took place from January to March 2003. Measurements were conducted onboard the Russian high-altitude research aircraft Geophysica using the low-pressure Condensation Nucleus Counter COPAS (COndensation PArticle Counter System) and a modified FSSP 300 (Forward Scattering Spectrometer Probe). Around 18–20 km altitude typical total particle number concentrations nt range at 10–20 cm−3 (ambient conditions). Correlations with the trace gases nitrous oxide (N2O) and trichlorofluoromethane (CFC-11) are discussed. Inside the polar vortex the total number of particles >0.01 μm increases with potential temperature while N2O is decreasing which indicates a source of particles in the above polar stratosphere or mesosphere. A separate channel of the COPAS instrument measures the fraction of aerosol particles non-volatile at 250°C. Inside the polar vortex a much higher fraction of particles contained non-volatile residues than outside the vortex (~67% inside vortex, ~24% outside vortex). This is most likely due to a strongly increased fraction of meteoric material in the particles which is transported downward from the mesosphere inside the polar vortex. The high fraction of non-volatile residual particles gives therefore experimental evidence for downward transport of mesospheric air inside the polar vortex. It is also shown that the fraction of non-volatile residual particles serves directly as a suitable experimental vortex tracer. Nanometer-sized meteoric smoke particles may also serve as nuclei for the condensation of gaseous sulfuric acid and water in the polar vortex and these additional particles may be responsible for the increase in the observed particle concentration at low N2O. The number concentrations of particles >0.4 μm measured with the FSSP decrease markedly inside the polar vortex with increasing potential temperature, also a consequence of subsidence of air from higher altitudes inside the vortex. Another focus of the analysis was put on the particle measurements in the lowermost stratosphere. For the total particle density relatively high number concentrations of several hundred particles per cm3 at altitudes below ~14 km were observed in several flights. To investigate the origin of these high number concentrations we conducted air mass trajectory calculations and compared the particle measurements with other trace gas observations. The high number concentrations of total particles in the lowermost stratosphere are probably caused by transport of originally tropospheric air from lower latitudes and are potentially influenced by recent particle nucleation.
Wolken haben einen maßgeblichen Einfluss auf den Wasserhaushalt der Erde, das Wettergeschehen und das Klima. Sie wissenschaftlich zu beschreiben, ist schwierig – und das erschwert die Niederschlagsvorhersage ebenso wie die Klimamodellierung. Wichtig für die Entstehung von Regen in unseren Breiten sind Eispartikel. Sie machen einen großen Teil der Wolken aus. Doch wie bilden sie sich, und warum sind sie für viele physikalische Prozesse in den Wolken unentbehrlich? Und schließlich: Wirkt sich menschliches Handeln auf die Wolken aus?
Two types of particles exist in the atmosphere, primary and secondary particles. While primary particles such as soot, mineral dust, sea salt particles or pollen are introduced directly as particles into the atmosphere, secondary particles are formed in the atmosphere by condensation of gases. The formation of such new aerosol particles takes place frequently and at a broad variety of atmospheric conditions and geographic locations. A considerable fraction of the atmospheric particles is formed by such nucleation processes. The newly formed particles may grow by condensation to sizes where they are large enough to act as cloud condensation nuclei and therefore may affect cloud properties. The fundamental processes of aerosol nucleation are described and typical atmospheric observations are discussed. Two recent studies are introduced that potentially change our current understanding of atmospheric nucleation substantially.
Non-forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, and are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely sensed biomass products and are undersampled by in situ monitoring. Current global change threats emphasize the need for new tools to capture biomass change in non-forest ecosystems at appropriate scales. Here we developed and deployed a new protocol for photogrammetric height using unoccupied aerial vehicle (UAV) images to test its capability for delivering standardized measurements of biomass across a globally distributed field experiment. We assessed whether canopy height inferred from UAV photogrammetry allows the prediction of aboveground biomass (AGB) across low-stature plant species by conducting 38 photogrammetric surveys over 741 harvested plots to sample 50 species. We found mean canopy height was strongly predictive of AGB across species, with a median adjusted R2 of 0.87 (ranging from 0.46 to 0.99) and median prediction error from leave-one-out cross-validation of 3.9%. Biomass per-unit-of-height was similar within but different among, plant functional types. We found that photogrammetric reconstructions of canopy height were sensitive to wind speed but not sun elevation during surveys. We demonstrated that our photogrammetric approach produced generalizable measurements across growth forms and environmental settings and yielded accuracies as good as those obtained from in situ approaches. We demonstrate that using a standardized approach for UAV photogrammetry can deliver accurate AGB estimates across a wide range of dynamic and heterogeneous ecosystems. Many academic and land management institutions have the technical capacity to deploy these approaches over extents of 1–10 ha−1. Photogrammetric approaches could provide much-needed information required to calibrate and validate the vegetation models and satellite-derived biomass products that are essential to understand vulnerable and understudied non-forested ecosystems around the globe.
We combine structural analysis of fractures with 22 U–Pb dates measured in fracture-filling carbonate cements from bed-parallel fibrous calcite veins (beef), conjugated veins and faults within the Vaca Muerta Formation along the Andean fold and thrust belt in the Neuquén Basin. The measured ages constrain accurately the relationships between overpressures caused by hydrocarbon generation and Andean compression as mechanisms for natural fracturing and vein formation. Two generations of fibres have been identified in beef. The first one, consists of dark fibres from the inner zones, which are perpendicular to bedding and contain abundant cone-in-cone structures and hydrocarbon inclusions. U–Pb dating of these fibres yielded Early to Late Cretaceous ages from 116.7 ± 17.7 to 78.8 ± 10.2 Ma. The second generation of fibres corresponds to the outer zones and consists of white fibres oblique to bedding, indicating growth during layer-parallel shortening. Bed-perpendicular veins cutting beef yielded Late Cretaceous-late Palaeocene dates from 72.8 ± 22.4 to 60.9 ± 10.4 Ma. Eocene ages from 52.0 ± 2.9 to 42.2 ± 18.9 Ma were measured in bed-parallel slip surfaces and reverse and strike-slip faults, whereas Miocene dates from 13.9 ± 2.6 to 6.2 ± 1.1 Ma were measured in E-W calcite veins. U–Pb dating of veins, structural analysis of fractures and subsidence curves, indicate that beef inner zones formed in the oil window during burial of the Neuquén basin, and that tectonic stresses could enhance their formation. Beef outer zones and bed-perpendicular veins formed during E-W Late Cretaceous-late Palaeocene layer-parallel shortening. Contrarily, late Palaeocene-late Eocene bed-parallel slip surfaces and faults and Miocene E-W veins formed during NE-SW and E-W syn-to post-folding deformation, respectively. In both cases, syn-to post-folding compression occurred synchronously with forelandward migration of magmatic activity attributed to flat subduction of the Pacific slab beneath the Andes.
A new, two-channel instrument for simultaneous NO3 and N2O5 monitoring was used to make the first comprehensive set of nocturnal NOx measurements (NO, NO2, NO3 and N2O5) at the Taunus Observatory, a rural mountain site (Kleiner Feldberg) in South-western Germany. In May 2008, NO3 and N2O5 mixing ratios were well above the instrumental detection limit (a few ppt) on all nights of the campaign and were characterised by large variability resulting from inhomogeneously distributed sinks. The concentrations of NO3, N2O5 and NO2 were consistent with the equilibrium constant, K2, defining the rates of formation and thermal dissociation of N2O5. A steady-state lifetime analysis showed that nocturnal NOx losses were generally dominated by reaction of NO3 with volatile organic compounds in this forested region, with N2O5 uptake to aerosols of secondary importance. Analysis of a limited dataset obtained at high relative humidity indicated that the loss of N2O5 by reaction with water vapour is less efficient (> factor 3) than derived using laboratory kinetic data. The fraction of NOx present as NO3 and N2O5 reached ≈20% on some nights, with night-time losses of NOx competing with daytime losses.
A new, two-channel instrument for simultaneous NO3 and N2O5 monitoring was used to make the first comprehensive set of nocturnal NOx measurements (NO, NO2, NO3 and N2O5) at the Taunus Observatory, a rural mountain site (Kleiner Feldberg) in South-western Germany. In May 2008, NO3 and N2O5 mixing ratios were well above the instrumental detection limit (a few ppt) on all nights of the campaign and were characterised by large variability. The concentrations of NO3, N2O5 and NO2 were consistent with the equilibrium constant, K2, defining the rates of formation and thermal dissociation of N2O5. A steady-state lifetime analysis is consistent with the loss of nocturnal NOx being dominated by the reaction of NO3 with volatile organic compounds in this forested region, with N2O5 uptake to aerosols of secondary importance. Analysis of a limited dataset obtained at high relative humidity indicated that the loss of N2O5 by reaction with water vapour is less efficient (>factor 3) than derived using laboratory kinetic data. The fraction of NOx present as NO3 and N2O5 reached ~20% on some nights, with night-time losses of NOx competing with daytime losses.
Global warming, changes in the hydrological cycle and enhanced marine primary productivity all have been invoked to have contributed to the occurrence of widespread ocean anoxia during the Cenomanian-Turonian Oceanic Anoxic Event (OAE2; ~ 94 Ma), but disentangling these factors on a regional scale has remained problematic. We generated palynological and organic geochemical records that allow the separation of these forcing factors in a core spanning the OAE2 from Wunstorf, Lower Saxony Basin (LSB; North Gemany), which exhibits cyclic black shale–marl alternations related to the orbital precession cycle.
Despite the widely varying depositional conditions complicating the interpretation of the obtained records, TEX86H indicates that sea-surface temperature (SST) evolution in the LSB during OAE2 resembles that of previously studied sites throughout the proto-North Atlantic. Cooling during the so-called Plenus Cold Event interrupted black shale deposition during the early stages of OAE2. However, TEX86 does not vary significantly across marl–black shale alternations, suggesting that temperature variations did not force the formation of the cyclic black shale horizons. Relative (i.e., with respect to marine palynomorphs) and absolute abundances of pollen and spores are elevated during phases of black shale deposition, indicative of enhanced precipitation and run-off. High abundances of cysts from inferred heterotrophic and euryhaline dinoflagellates supports high run-off, which likely introduced additional nutrients to the epicontinental shelf resulting in elevated marine primary productivity.
We conclude that orbitally-forced enhanced precipitation and run-off, in tandem with elevated marine primary productivity, were critical in cyclic black shale formation on the northwest European epicontinental shelf and potentially for other OAE2 sections in the proto-Atlantic and Western Interior Seaway at similar latitudes as well.
Reconstructing the early Paleogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Paleogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Paleocene to the early Eocene (60.7–54.2 Ma) based on a sporomorph record from Ocean Drilling Program (ODP) Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Paleocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Paleocene; (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians across the middle/late Paleocene transition interval (~59.5 to ~59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Paleocene–Eocene Thermal Maximum (PETM). The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e., palms and cycads) across the middle/late Paleocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the comparison of our season-specific climate estimates for the sporomorph assemblages from ODP Site 1172 with the TEX86L- and TEX86H-based temperature data suggests a warm-season bias of both calibrations for the early Paleogene of the high southern latitudes.
Terrestrial climate and ecosystem evolution during ‘Greenhouse Earth’ phases of the early Paleogene remain incompletely known. Particularly, paleobotanical records from high southern latitudes are giving only limited insights into the Paleocene and early Eocene vegetation of the region. Hence, data from continuous well-calibrated sequences are required to make progress with the reconstruction of terrestrial climate and ecosystem dynamics from the southern latitudes during the early Paleogene.
In order to elucidate the terrestrial conditions from the high southern latitudes during the early Paleogene, terrestrial palynology was applied in the present study to two well-dated deep-marine sediment cores located at the Australo-Antarctic region: (i) IODP Site U1356 (Wilkes Land margin, East Antarctica) and (ii) ODP Site 1172 (East Tasman Plateau, southwest Pacific Ocean). The studied sequence from IODP Site U1356 comprises mid-shelfal sediments from the early to middle Eocene (53.9 – 46 million years ago [Ma]). For the ODP Site 1172, the studied succession is characterized by sediments deposited in shallow marine environments of the middle Paleocene to the early Eocene (60.7 – 54.2 Ma).
Based on the obtained pollen and spores (sporomorphs) results from the studied sequences of Site U1356 and Site 1172, this study aims to: (1) decipher the terrestrial climate conditions along the Australo-Antarctic region from the middle Paleocene to the middle Eocene; (2) evaluate the structure, diversity and compositional patterns of forests that throve in the Australo-Antarctic region during the early Paleogene; (3) understand the response of forests from the high southern latitudes to the climate dynamics from the early Paleogene; (4) establish a connection between the generated terrestrial palynomorph data and published Sea Surface Temperatures (SSTs) from the same cores.
To decipher the terrestrial climatic conditions on the Australo-Antarctic region, this study relies on the nearest living relative (NLR) concept that assumes that fossil taxa have similar climate requirements as their modern counterparts. This approach was applied to the sporomorph results of Site U1356 and Site 1172, following mainly the bioclimatic analysis. With regard to the structure and diversity patterns of the vegetation from the same region, the present study presents combined qualitative (i.e., reconstruction of the vegetation based mainly on the habitats of the known living relatives) and quantitative (i.e., application of ordination techniques, rarefaction and diversity indices) analyses of the fossil sporomorphs results.
The overall results from the paleoclimatic and vegetation reconstruction approaches applied in the present study, indicate that temperate and paratropical forests during the early Paleogene throve under different climatic conditions on the Wilkes Land margin and on Tasmania, at paleolatitudes of ∼70°S and ∼65°S, respectively.
Specifically, the sporomorph results from Site U1356, suggest that a highly diverse forest similar to present-day forests from New Caledonia was thriving on Antarctica during the early Eocene (53.9 – 51.9 Ma). These forests were characterized by the presence of termophilous taxa that are restricted today to tropical and subtropical settings, notably Bombacoideae, Strasburgeria, Beauprea, Spathiphyllum, Anacolosa and Lygodium. In combination with MBT/CBT paleotemperature results, they provide strong evidence for near-tropical warmth at least in the coastal lowlands along the Wilkes Land margin. The coeval presence of frost tolerant taxa such as Nothofagus, Araucariaceae and Podocarpaceae during the early Eocene on the same record suggests that paratropical forests were thriving along the Wilkes Land margin. Due to the presence of this kind of vegetation, it is possible to suggest that forests in this region were subject to a climatic gradient related to differences in elevation and/or the proximity to the coastline.
By the middle Eocene, the paratropical forests that characterized the vegetation of the early Eocene on the Wilkes Land margin were replaced by low diversity temperate forests dominated by Nothofagus, and similar to present-day cool-temperate forests from New Zealand. The dominance of these forests and the absence of thermophilous elements together with the lower temperatures suggested by the MBT/CBT and the sporomorph-based temperatures indicate consistently cooler conditions during this time interval.
With regard to the sporomorph results of Site 1172, this study suggests that three vegetation types were thriving on Tasmania from the middle Paleocene to the early Eocene under different climatic conditions. During the middle to late Paleocene, warm-temperate forests dominated by Podocarpaceae and Araucariaceae were the prevailing vegetation on Tasmania. The dominance of these forests was interrupted by the transient predominance of cool-temperate forests dominated by Nothofagus and Araucariaceae across the middle/late Paleocene transition interval (~59.5 to ~59.0 Ma). This cool-temperate forest was characterized by a lack of frost-sensitive elements (i.e., palms and cycads) indicating cooler conditions with harsher winters on Tasmania during this time interval. By the early Eocene, and linked with the Paleocene Eocene Thermal Maximum (PETM), Paleocene temperate forests dominated by gymnosperms were replaced by paratropical rainforests with the remarkable presence of the tropical mangrove palm Nypa during the PETM and the earliest Eocene. The overall results from Site U1356 and Site 1172, provide a new assessment of the terrestrial climatic conditions in the Australo-Antarctic region for validating climate models and understanding the response of high-latitude terrestrial ecosystems to the climate dynamics of the early Paleogene on southern latitudes.
The climatic conditions in the higher latitudes during the early Paleogene were further unravelled by comparing the obtained terrestrial and marine results. The integration of the obtained sporomorph data with previously published TEX86-based SSTs from Site 1172 documents that the vegetation dynamics were closely linked with the temperature evolution from the Australo-Antarctic region. Moreover, the comparison of TEX86-based SSTs and sporomorph-based climatic estimations from Site 1172 suggests a warm-season bias of both calibrations of TEX86 (i.e., TEX86Hand TEX86H), when this proxy is applied to high southern latitudes records of the early Paleogene.
The mechanisms of transfer of crustal material from the subducting slab to the overlying mantle wedge are still debated. Mélange rocks, formed by mixing of sediments, oceanic crust, and ultramafics along the slab-mantle interface, are predicted to ascend as diapirs from the slab-top and transfer their compositional signatures to the source region of arc magmas. However, the compositions of melts that result from the interaction of mélanges with a peridotite wedge remain unknown. Here we present experimental evidence that melting of peridotite hybridized by mélanges produces melts that carry the major and trace element abundances observed in natural arc magmas. We propose that differences in nature and relative contributions of mélanges hybridizing the mantle produce a range of primary arc magmas, from tholeiitic to calc-alkaline. Thus, assimilation of mélanges into the wedge may play a key role in transferring subduction signatures from the slab to the source of arc magmas.
Talc formation via silica-metasomatism of ultramafic rocks is believed to play key roles in subduction zone processes. Yet, the conditions of talc formation remain poorly constrained. We used thermodynamic reaction-path models to assess the formation of talc at the slab-mantle interface and show that it is restricted to a limited set of pressure–temperature conditions, protolith, and fluid compositions. In contrast, our models predict that chlorite formation is ubiquitous at conditions relevant to the slab-mantle interface of subduction zones. The scarcity of talc and abundance of chlorite is evident in the rock record of exhumed subduction zone terranes. Talc formation during Si-metasomatism may thus play a more limited role in volatile cycling, strain localization, and in controlling the decoupling-coupling transition of the plate interface. Conversely, the observed and predicted ubiquity of chlorite corroborates its prominent role in slab-mantle interface processes that previous studies attributed to talc.
Key Points:
Limited talc formation by Si-metasomatism of ultramafic rocks in subduction zones
Chlorite formation is likely pervasive at the slab-mantle interface
Preferential formation of chlorite has wide-ranging chemical and physical implications for subduction zone processes
Plain Language Summary: In subduction zones, talc can form during chemical reactions of mantle rocks with silica-enriched fluids at the interface between descending oceanic plates and the overriding mantle. Its formation and distribution in subduction zones are believed to affect the volatile budget, rheological properties, and the down-dip limit of the decoupling of the slab-mantle interface. Therefore, illuminating the conditions that facilitate talc formation at high pressure-temperature conditions is key in assessing its roles in fundamental subduction zone processes. Using thermodynamic reaction-path models, we show that the formation of talc at the slab-mantle interface is restricted to a limited set of environmental conditions, because its formation is highly sensitive to the compositions of the mantle rocks and reactant fluids. Contrary to common belief, talc is unlikely to form in high abundance in ultramafic rocks metasomatized by Si-rich slab-derived fluids. Rather, our models predict the ubiquitous formation of chlorite along with other silicate minerals during Si-metasomatism due to the competing effects from other dissolved components that favor their formation over talc. This study calls into question the importance of talc during Si-metasomatism in subduction zones but highlights the more predominant role of chlorite.
Metasomatic reaction zones between mafic and ultramafic rocks exhumed from subduction zones provide a window into mass-transfer processes at high pressure. However, accurate interpretation of the rock record requires distinguishing high-pressure metasomatic processes from inherited oceanic signatures prior to subduction. We integrated constraints from bulk-rock geochemical compositions and petrophysical properties, mineral chemistry, and thermodynamic modeling to understand the formation of reaction zones between juxtaposed metagabbro and serpentinite as exemplified by the Voltri Massif (Ligurian Alps, Italy). Distinct zones of variably metasomatized metagabbro are dominated by chlorite, amphibole, clinopyroxene, epidote, rutile, ilmenite, and titanite between serpentinite and eclogitic metagabbro. Whereas the precursor serpentinite and oxide gabbro formed and were likely already in contact in an oceanic setting, the reaction zones formed by diffusional Mg-metasomatism between the two rocks from prograde to peak, to retrograde conditions in a subduction zone. Metasomatism of mafic rocks by Mg-rich fluids that previously equilibrated with serpentinite could be widespread along the subduction interface, within the subducted slab, and the mantle wedge. Furthermore, the models predict that talc formation by Si-metasomatism of serpentinite in subduction zones is limited by pressure-dependent increase in the silica activity buffered by the serpentine-talc equilibrium. Elevated activities of aqueous Ca and Al species would also favor the formation of chlorite and garnet. Accordingly, unusual conditions or processes would be required to stabilize abundant talc at high P-T conditions. Alternatively, a different set of mineral assemblages, such as serpentine- or chlorite-rich rocks, may be controlling the coupling-decoupling transition of the plate interface.
Small-scale thermal upwellings under the northern East African Rift from S travel time tomography
(2016)
There is a long-standing debate over how many and what types of plumes underlie the East African Rift and whether they do or do not drive its extension and consequent magmatism and seismicity. Here we present a new tomographic study of relative teleseismic S and SKS residuals that expands the resolution from previous regional studies below the northern East African Rift to image structure from the surface to the base of the transition zone. The images reveal two low-velocity clusters, below Afar and west of the Main Ethiopian Rift, that extend throughout the upper mantle and comprise several smaller-scale (about 100 km diameter), low-velocity features. These structures support those of our recent P tomographic study below the region. The relative magnitude of S to P residuals is around 3.5, which is consistent with a predominantly thermal nature of the anomalies. The S and P velocity anomalies in the low-velocity clusters can be explained by similar excess temperatures in the range of 100–200°C, consistent with temperatures inferred from other seismic, geochemical, and petrological studies. Somewhat stronger VS anomalies below Afar than west of the Main Ethiopian Rift may include an expression of volatiles and/or melt in this region. These results, together with a comparison with previous larger-scale tomographic models, indicate that these structures are likely small-scale upwellings with mild excess temperatures, rising from a regional thermal boundary layer at the base of the upper mantle.
Die Meteor-Reise 60 besteht aus 5 Fahrtabschnitten im subtropischen Wirbel des Nordatlantiks von den Azoren bzw. Madeira bis zum tropischen Westatlantik. Fahrtabschnitt 1 konzentriert sich auf die Ökologie und Biogeochemie von sogenannten „Seamounts“ im östlichen Atlantik im Rahmen eines EU-Projektes; Fahrtabschnitt 2 umfasst, in Zusammenarbeit mit französischen Kollegen, detailierte seismische und geophysikalische Untersuchungen eines aktiven Segments des Mittelatlantischen Rückens; Fahrtabschnitt 3 ist eine multidisziplinäre (geologisch, biologisch und chemisch) Untersuchung über die Auswirkungen der hydrothermalen Zirkulation am Mittelatlantischen Rücken im Rahmen eines DFG-Schwerpunkt-programms; Fahrtabschnitt 4 ist einer physikalisch-ozeanographische Studie der langfristigen Variation der thermohalien Zirkulation in westlichen Becken des Atlantiks im Kontext des BMBF-CLIVAR programms gewidmet; und Fahrtabschnitt 5 schließlich, ist eine multidisziplinäre (chemisch/biologisch) Untersuchung über die CO2-Aufnahme und die biologische Pumpe in der Wassersäule des nordatlantischen Subtropenwirbels (DFG-Sonderforschungsbereich 460). Der erste Fahrtabschnitt der Reise M 60 dient der physikalischen, biogeochemischen und biologischen Probengewinnung im Rahmen des EU- Projektes OASIS (OceAnic Seamounts: an Integrated Study). OASIS ist ein interdisziplinäres Projekt mit 9 Partnern aus 5 europäischen Ländern und untersucht die funktionale Charakteristik von Seamount-Ökosystemen. Basierend auf 2 Fallstudien werden die Prozesse, die Seamount-Ökosysteme charakterisieren, und ihre Einflüsse auf den umgebenden Ozean beschrieben. Die wissenschaftlichen Ergebnisse, zusammengeführt in einem konzeptionellen Ökosystemmodell, werden Ausgangsbasis für die Entwicklung von generellen und ortspezifischen Managementplänen sein. Das primäre Ziel von OASIS, eine holistische Erfassung von Seamount-Ökosystemen, wird durch die Integration folgender Sachgebiete erreicht: a) Identifikation und Beschreibung der physikalischen Einflußkräfte auf Seamount-Ökosysteme b) Erfassung der Herkunft, Qualität und Dynamik partikulärer organischer Substanz in der Wassersäule und an der Sedimentoberfläche c) Beschreibung von Aspekten der Biodiversität und Ökologie von Seamount-Lebensgemeinschaften und Erfassung ihrer Dynamik und Produktionsmechanismen d) Modellierung der trophischen Ökologie von Seamount-Ökosystemen e) Anwendung der wissenschaftlichen Ergebnisse auf den Naturschutz. Ein weiteres Ziel der Fahrt ist die Erprobung eines neu entwickelten Drucklabors zur Untersuchung von Tiefseeorganismen unter in situ-Druckbdingenungen von bis zu 500 bar.
140 Liter Wasser werden für die Herstellung einer Tasse Kaffee benötigt, 1.300 Liter Wasser für ein Kilo Gerste und 3.400 Liter Wasser für ein Kilo Reis. Diese Zahlen mögen im ersten Moment unglaubwürdig erscheinen, doch sie entsprechen der Wirklichkeit. Für die Herstellung von nahezu allen Produkten wird Wasser in teils sogar sehr großen Mengen benötigt. In dem Endprodukt jedoch findet sich meist nur ein kleiner Teil des ursprünglich eingesetzten Wassers in seiner physischen Form wieder. Der überwiegende Anteil wurde während des Produktionsprozesses verdunstet oder zur Kühlung eingesetzt und wird daher als „virtuelles Wasser“ bezeichnet. Aufgrund des Exports und Imports von Produkten im Zuge des internationalen Handels kommt es somit auch zu Strömen von virtuellem Wasser zwischen den einzelnen Ländern. In dieser Bachelorarbeit wird der virtuelle Wasserhandel mit 23 verschiedenen Feldfrüchten mit dem Fokus auf Deutschland für den Zeitraum von 1998 bis 2002 untersucht. In die Berechnung dieser virtuellen Wasserströme ist ein neuartiges Modell eingegangen, das Global Crop Water Model (GCWM), welches den virtuellen Wassergehalt für unterschiedliche Feldfruchtgruppen global für jede 5-Minuten-Zelle auf Basis detaillierter Daten berechnet. Dank dieses Modells ist es möglich, eine Trennung zwischen dem virtuellen Wasser, welches aus der Nutzung des Niederschlagswassers und dem virtuellen Wasser, welches aus der Bewässerung von Ackerflächen resultiert, vorzunehmen und diese getrennt von einander zu analysieren. Mittels der Verwendung der Handelsstatistik Comtrade der Vereinten Nationen lässt sich aus den Ergebnissen des GCWM der virtuelle Wasserhandel darstellen. Es zeigt sich, dass Deutschland das meiste Wasser in seiner virtuellen Form nach Algerien, Saudi-Arabien, Belgien und in die Niederlande exportiert, wohingegen aus Brasilien, den USA, Frankreich und der Elfenbeinküste die größten virtuellen Wassermengen importiert werden.
First-principles modeling techniques offer the ability to simulate a wide range of systems under different physical conditions, such as temperature, pressure, and composition, without relying on empirical knowledge. Density functional theory (DFT), a quantum mechanical method, has become an exceptionally successful framework for materials science modeling. Employing DFT makes it possible to gain valuable insights into the fundamental state of a system, enabling the reliable determination of equilibrium crystal structures. Over time, DFT has become an essential tool that can be incorporated into various schemes for predicting the properties of a material related to its structure, insulating/metallic behavior, magnetism, and optics. DFT is regularly applied in numerous fields, spanning from fundamental subjects in condensed matter physics to the study of large-scale phenomena in geosciences. In the latter, the effectiveness of DFT stems from its ability to simulate the properties found on the Earth, other planets, and meteorites, which may pose challenges for their direct study or laboratory investigation.
In this thesis, a comprehensive examination of a family of monosulfides and a perovskite heterostructure was conducted. These materials are relevant for their potential applications in technology, energy harvesting, and in the case of monosulfides, their speculated abundance on the planet Mercury.
Firstly, a DFT approach was used to analyze two non-magnetic monosulfides, CaS and MgS. We determined their structural properties and then focused on the modeling of their reflectivity in the infrared region. The calculation of the reflectivity considered both harmonic and anharmonic contributions. In the harmonic limit, the non-analytic correction was employed to accurately determine the LO/TO splitting, which is necessary to delimit the retstrahlend band, that is, the maximum of the reflectivity. The anharmonic effects given by up to three-phonon and isotopic scatterings, which were included using perturbation theory, primarily smeared the reflectivity spectra edges in the high-wave region.
Secondly, four polymorphs of MnS were studied using a combination of first-principles methods to simulate their antiferromagnetic (AFM) and paramagnetic (PM) states. The integration of DFT+$U$ with special quasirandom structures (SQS) supercells, and occupation matrix control techniques was crucial for achieving convergence, structural optimization accuracy, and obtaining finite energy band gaps and local magnetic moments in the PM phases. The addition of the Hubbard $U$ correction was necessary to treat the highly-correlated Mn $d$-electrons. The success of our approach was clear based on our electronic structure predictions for the PM rock-salt B1-MnS polymorph. Experimentally this phase has been observed to be an insulator, but multiple \emph{ab initio} works resulted previously in metallic behavior. Our computations, on the other hand, predicted insulating and magnetic properties that compare well with available measurements. Additionally, the pressure-field stability of the four MnS polymorphs was studied. In the case of the PM phases, B1-MnS was identified to be the most stable up to about 21 GPa, then transforming into the B31-MnS polymorph. This finding was in close agreement with high-pressure experiments reporting a similar phase transformation. The optical properties of B1-, B4-, and B31-MnS were also simulated. The SQS technique was used to obtain soft-mode-free phonon band structures within the harmonic approximation. Then, the anharmonic effects were included, and the reflectivity was calculated for B1-MnS and B4-MnS. In both cases, a good agreement for the LO/TO splitting was achieved in comparison to experimental results.
Lastly, the oxygen-deficient heterostructure of LaAlO$_{3-\delta}$ /SrTiO$_{3-\delta}$ was investigated also employing DFT+$U$, with a particular emphasis on the potential impact of vacancy clustering at the interface. Six distinct configurations of pairs of vacancies were studied and their energies were compared to find the most stable one. The orbital reconstruction of Ti orbitals was also examined based on their location with respect to the vacancies and the local magnetic moments were calculated. The final results showed that linearly arranged vacancies located opposite to Ti ions give the most energetically stable configuration.
We report on HCFC-22 data acquired by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) in the reduced spectral resolution nominal observation mode. The data cover the period from January 2005 to April 2012 and the altitude range from the upper troposphere (above cloud top altitude) to about 50 km. The profile retrieval was performed by constrained nonlinear least squares fitting of modelled spectra to the measured limb spectral radiances. The spectral ν4-band at 816.5 ± 13 cm−1 was used for the retrieval. A Tikhonov-type smoothing constraint was applied to stabilise the retrieval. In the lower stratosphere, we find a global volume mixing ratio of HCFC-22 of about 185 pptv in January 2005. The rate of linear growth in the lower latitudes lower stratosphere was about 6 to 7 pptv year−1 in the period 2005–2012. The profiles obtained were compared with ACE-FTS satellite data v3.5, as well as with MkIV balloon profiles and cryosampler balloon measurements. Between 13 and 22 km, average agreement within −3 to +5 pptv (MIPAS – ACE) with ACE-FTS v3.5 profiles is demonstrated. Agreement with MkIV solar occultation balloon-borne measurements is within 10–20 pptv below 30 km and worse above, while in situ cryosampler balloon measurements are systematically lower over their full altitude range by 15–50 pptv below 24 km and less than 10 pptv above 28 km. MIPAS HCFC-22 time series below 10 km altitude are shown to agree mostly well to corresponding time series of near-surface abundances from the NOAA/ESRL and AGAGE networks, although a more pronounced seasonal cycle is obvious in the satellite data. This is attributed to tropopause altitude fluctuations and subsidence of polar winter stratospheric air into the troposphere. A parametric model consisting of constant, linear, quasi-biennial oscillation (QBO) and several sine and cosine terms with different periods has been fitted to the temporal variation of stratospheric HCFC-22 for all 10°-latitude/1-to-2-km-altitude bins. The relative linear variation was always positive, with relative increases of 40–70 % decade−1 in the tropics and global lower stratosphere, and up to 120 % decade−1 in the upper stratosphere of the northern polar region and the southern extratropical hemisphere. Asian HCFC-22 emissions have become the major source of global upper tropospheric HCFC-22. In the upper troposphere, monsoon air, rich in HCFC-22, is instantaneously mixed into the tropics. In the middle stratosphere, between 20 and 30 km, the observed trend is inconsistent with the trend at the surface (corrected for the age of stratospheric air), hinting at circulation changes. There exists a stronger positive trend in HCFC-22 in the Southern Hemisphere and a more muted positive trend in the Northern Hemisphere, implying a potential change in the stratospheric circulation over the observation period.
We report on HCFC-22 data acquired by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) in reduced spectral resolution nominal mode in the period from January 2005 to April 2012 from version 5.02 level-1b spectral data and covering an altitude range from the upper troposphere (above cloud top altitude) to about 50 km. The profile retrieval was performed by constrained nonlinear least squares fitting of measured limb spectral radiances to modelled spectra. The spectral v4-band at 816.5 ± 13 cm-1 was used for the retrieval. A Tikhonov-type smoothing constraint was applied to stabilise the retrieval. In the lower stratosphere, we find a global volume mixing ratio of HCFC-22 of about 185 pptv in January 2005. The linear growth rate in the lower latitudes lower stratosphere was about 6 to 7 pptv yr-1 in the period 2005–2012. The obtained profiles were compared with ACE-FTS satellite data v3.5, as well as with MkIV balloon profiles and in situ cryosampler balloon measurements. Between 13 and 22 km, average agreement within -3 to +5 pptv (MIPAS–ACE) with ACE-FTS v3.5 pro files is demonstrated. Agreement with MkIV solar occultation balloon-borne measurements is within 10–20 pptv below 30 km and worse above, while in situ cryosampler balloon measurements are systematically lower over their full altitude range by 15– 50 pptv below 24 km and less than 10 pptv above 28 km. Obtained MIPAS HCFC-22 time series below 10 km altitude are shown to agree mostly well to corresponding time series of near-surface abundances from NOAA/ESRL and AGAGE networks, although a more pronounced seasonal cycle is obvious in the satellite data, probably due to tropopause altitude fluctuations and subsidence of polar winter stratospheric air into the troposphere. A parametric model consisting of constant, linear, quasi-biennial oscillation (QBO) and several sine and cosine terms with different periods has been fitted to the temporal variation of stratospheric HCFC-22 for all 10° latitude/1 to 2 km altitude bins. The relative linear variation was always positive, with relative increases of 40–70%decade-1 in the tropics and global lower stratosphere, and up to 120%decade-1 in the upper stratosphere of the northern polar region and the southern extratropical hemisphere. In the middle stratosphere between 20 and 30 km, the observed trend is not consistent with the age of stratospheric air-corrected trend at ground, but stronger positive at the Southern Hemisphere and less strong increasing in the Northern Hemisphere, hinting towards changes in the stratospheric circulation over the observation period.
Highlights
• Constrictional structures range from dome-and-basin folds to coeval folds and boudins.
• Under bulk constriction, the competent layer rotates slower than a passive plane.
• Extension-parallel and –perpendicular folds grow simultaneously.
• Extension-perpendicular folds affect previous boudins.
Abstract
We conducted scaled analogue modelling to show the influence of varying single layer initial orientation on the geometry of folds and boudins in a bulk constrictional strain field. The initial angle between the plane of shortening and the competent layer (θZ(i)) was incrementally increased from 0° to 90° by multiples of 11.25°. While the amount of layer thickening decreased with increasing θZ(i), the deformation structures produced range from pure dome-and-basin folds to coeval folds and boudins. Based on the attitude of fold axes, there are extension-parallel (FEPR) and extension-perpendicular (FEPP) folds, with axes subparallel and subperpendicular to the principal stretching axis (X), respectively. Coeval growth of FEPR folds and boudins occurred when θZ(i) > ca. 25°. The FEPP folds can be subdivided into a first type which affect the entire layer (if θZ(i) ranges between 11.25 and 78.75°) and a second type, referred to as FBEPP folds, which are affecting pre-existing boudins if θZ(i) > 45°. The interlimb angle of all types of folds increases with increasing θZ(i). Folds and boudins similar to the ones produced in this study can be found in salt domes and in tectonites of subduction zones.
Current atmospheric models do not include secondary organic aerosol (SOA) production from gas-phase reactions of polycyclic aromatic hydrocarbons (PAHs). Recent studies have shown that primary semivolatile emissions, previously assumed to be inert, undergo oxidation in the gas phase, leading to SOA formation. This opens the possibility that low-volatility gas-phase precursors are a potentially large source of SOA. In this work, SOA formation from gas-phase photooxidation of naphthalene, 1-methylnaphthalene (1-MN), 2-methylnaphthalene (2-MN), and 1,2-dimethylnaphthalene (1,2-DMN) is studied in the Caltech dual 28-m3 chambers. Under high-NOx conditions and aerosol mass loadings between 10 and 40 microg m-3, the SOA yields (mass of SOA per mass of hydrocarbon reacted) ranged from 0.19 to 0.30 for naphthalene, 0.19 to 0.39 for 1-MN, 0.26 to 0.45 for 2-MN, and constant at 0.31 for 1,2-DMN. Under low-NOx conditions, the SOA yields were measured to be 0.73, 0.68, and 0.58, for naphthalene, 1-MN, and 2-MN, respectively. The SOA was observed to be semivolatile under high-NOx conditions and essentially nonvolatile under low-NOx conditions, owing to the higher fraction of ring-retaining products formed under low-NOx conditions. When applying these measured yields to estimate SOA formation from primary emissions of diesel engines and wood burning, PAHs are estimated to yield 3–5 times more SOA than light aromatic compounds. PAHs can also account for up to 54% of the total SOA from oxidation of diesel emissions, representing a potentially large source of urban SOA.
Current atmospheric models do not include secondary organic aerosol (SOA) production from gas-phase reactions of polycyclic aromatic hydrocarbons (PAHs). Recent studies have shown that primary semivolatile emissions, previously assumed to be inert, undergo oxidation in the gas phase, leading to SOA formation. This opens the possibility that low-volatility gas-phase precursors are a potentially large source of SOA. In this work, SOA formation from gas-phase photooxidation of naphthalene, 1-methylnaphthalene (1-MN), 2-methylnaphthalene (2-MN), and 1,2-dimethylnaphthalene (1,2-DMN) is studied in the Caltech dual 28-m3 chambers. Under high-NOx conditions and aerosol mass loadings between 10 and 40 μg m, the SOA yields (mass of SOA per mass of hydrocarbon reacted) ranged from 0.19 to 0.30 for naphthalene, 0.19 to 0.39 for 1-MN, 0.26 to 0.45 for 2-MN, and constant at 0.31 for 1,2-DMN. Under low-NOx conditions, the SOA yields were measured to be 0.73, 0.68, and 0.58, for naphthalene, 1-MN, and 2-MN, respectively. The SOA was observed to be semivolatile under high-NOx conditions and essentially nonvolatile under low-NOx conditions, owing to the higher fraction of ring-retaining products formed under low-NOx conditions. When applying these measured yields to estimate SOA formation from primary emissions of diesel engines and wood burning, PAHs are estimated to yield 3–5 times more SOA than light aromatic compounds. PAHs can also account for up to 54% of the total SOA from oxidation of diesel emissions, representing a potentially large source of urban SOA.
PolarCAP – A deep learning approach for first motion polarity classification of earthquake waveforms
(2022)
Highlights
• We present PolarCAP, a deep learning model that can classify the polarity of a waveform with a 98% accuracy.
• The first-motion polarity of seismograms is a useful parameter, but its manual determination can be laborious and imprecise.
• We demonstrate that in several cases the model can assign trace polar-ity more accurately than a human analyst.
Abstract
The polarity of first P-wave arrivals plays a significant role in the effective determination of focal mechanisms specially for smaller earthquakes. Manual estimation of polarities is not only time-consuming but also prone to human errors. This warrants a need for an automated algorithm for first motion polarity determination. We present a deep learning model - PolarCAP that uses an autoencoder architecture to identify first-motion polarities of earth-quake waveforms. PolarCAP is trained in a supervised fashion using more than 130,000 labelled traces from the Italian seismic dataset (INSTANCE) and is cross-validated on 22,000 traces to choose the most optimal set of hyperparameters. We obtain an accuracy of 0.98 on a completely unseen test dataset of almost 33,000 traces. Furthermore, we check the model generalizability by testing it on the datasets provided by previous works and show that our model achieves a higher recall on both positive and negative polarities.
The Weissert Event ~133 million years ago marked a profound global cooling that punctuated the Early Cretaceous greenhouse. We present modelling, high-resolution bulk organic carbon isotopes and chronostratigraphically calibrated sea surface temperature (SSTs) based on an organic paleothermometer (the TEX86 proxy), which capture the Weissert Event in the semi-enclosed Weddell Sea basin, offshore Antarctica (paleolatitude ~54 °S; paleowater depth ~500 meters). We document a ~3–4 °C drop in SST coinciding with the Weissert cold end, and converge the Weddell Sea data, climate simulations and available worldwide multi-proxy based temperature data towards one unifying solution providing a best-fit between all lines of evidence. The outcome confirms a 3.0 °C ( ±1.7 °C) global mean surface cooling across the Weissert Event, which translates into a ~40% drop in atmospheric pCO2 over a period of ~700 thousand years. Consistent with geologic evidence, this pCO2 drop favoured the potential build-up of local polar ice.
Biogenic organic precursors play an important role in atmospheric new particle formation (NPF). One of the major precursor species is α-pinene, which upon oxidation can form a suite of products covering a wide range of volatilities. Highly oxygenated organic molecules (HOMs) comprise a fraction of the oxidation products formed. While it is known that HOMs contribute to secondary organic aerosol (SOA) formation, including NPF, they have not been well studied in newly formed particles due to their very low mass concentrations. Here we present gas- and particle-phase chemical composition data from experimental studies of α-pinene oxidation, including in the presence of isoprene, at temperatures (−50 and −30 ∘C) and relative humidities (20 % and 60 %) relevant in the upper free troposphere. The measurements took place at the CERN Cosmics Leaving Outdoor Droplets (CLOUD) chamber. The particle chemical composition was analyzed by a thermal desorption differential mobility analyzer (TD-DMA) coupled to a nitrate chemical ionization–atmospheric pressure interface–time-of-flight (CI-APi-TOF) mass spectrometer. CI-APi-TOF was used for particle- and gas-phase measurements, applying the same ionization and detection scheme. Our measurements revealed the presence of C8−10 monomers and C18−20 dimers as the major compounds in the particles (diameter up to ∼ 100 nm). Particularly, for the system with isoprene added, C5 (C5H10O5−7) and C15 compounds (C15H24O5−10) were detected. This observation is consistent with the previously observed formation of such compounds in the gas phase. However, although the C5 and C15 compounds do not easily nucleate, our measurements indicate that they can still contribute to the particle growth at free tropospheric conditions. For the experiments reported here, most likely isoprene oxidation products enhance the growth of particles larger than 15 nm. Additionally, we report on the nucleation rates measured at 1.7 nm (J1.7 nm) and compared with previous studies, we found lower J1.7 nm values, very likely due to the higher α-pinene and ozone mixing ratios used in the present study.
Biogenic organic precursors play an important role in atmospheric new particle formation (NPF). One of the major precursor species is α-pinene, which upon oxidation can form a suite of products covering a wide range of volatilities. Highly oxygenated organic molecules (HOMs) comprise a fraction of the oxidation products formed. While it is known that HOMs contribute to secondary organic aerosol (SOA) formation, including NPF, they have not been well studied in newly formed particles due to their very low mass concentrations. Here we present gas- and particle-phase chemical composition data from experimental studies of α-pinene oxidation, including in the presence of isoprene, at temperatures (−50 and −30 ∘C) and relative humidities (20 % and 60 %) relevant in the upper free troposphere. The measurements took place at the CERN Cosmics Leaving Outdoor Droplets (CLOUD) chamber. The particle chemical composition was analyzed by a thermal desorption differential mobility analyzer (TD-DMA) coupled to a nitrate chemical ionization–atmospheric pressure interface–time-of-flight (CI-APi-TOF) mass spectrometer. CI-APi-TOF was used for particle- and gas-phase measurements, applying the same ionization and detection scheme. Our measurements revealed the presence of C8−10 monomers and C18−20 dimers as the major compounds in the particles (diameter up to ∼ 100 nm). Particularly, for the system with isoprene added, C5 (C5H10O5−7) and C15 compounds (C15H24O5−10) were detected. This observation is consistent with the previously observed formation of such compounds in the gas phase. However, although the C5 and C15 compounds do not easily nucleate, our measurements indicate that they can still contribute to the particle growth at free tropospheric conditions. For the experiments reported here, most likely isoprene oxidation products enhance the growth of particles larger than 15 nm. Additionally, we report on the nucleation rates measured at 1.7 nm (J1.7 nm) and compared with previous studies, we found lower J1.7 nm values, very likely due to the higher α-pinene and ozone mixing ratios used in the present study.
Atmospheric particles play an important role in the radiative balance of the Earth, as well as they affect human health and air quality. Hence, the chemical characterization constitutes a crucial task to determinate their properties, sources and fate. Particularly, the analysis of nanoparticles (d<100 nm) represents an analytical challenge, since these particles are abundant in number but have very little mass.
This accumulative thesis focuses on the chemical characterization of nanoparticles, performed in both laboratory and field studies. Here, I present four manuscripts, two of which are my main project as a lead author.
The first manuscript (Caudillo et al., 2021) focuses on the gas and the particle phase originated from biogenic precursor gases (α-pinene and isoprene). The experiments were performed in the CLOUD chamber at CERN to simulate pure biogenic new particle formation. Both gas and particle phases are measured with a nitrate CI-APi-TOF mass spectrometer, while the TD-DMA is coupled to it for particle-phase measurements, this setup allows a direct comparison as both measurements use the identical chemical ionization and detector. This study demonstrates the suitability of the TD-DMA for measuring newly formed nanoparticles and it confirms that isoprene suppresses new particle formation but contributes to the growth of newly formed particles.
The second manuscript (Caudillo et al., 2022) presents an intercomparison of four different techniques (including the TD-DMA) for measuring the chemical composition of SOA nanoparticles. The measurements were conducted in the CLOUD chamber. The intercomparison was done by contrasting the observed chemical composition, the calculated volatility, and the thermal desorption behavior (for the thermal desorption techniques). The methods generally agreed on the most important compounds that are found in the nanoparticles. However, they did see different parts of the organic spectrum. Potential explanations for these differences are suggested.
The third manuscript (Ungeheuer al., 2022) presents both laboratory and ambient measurements to investigate the ability of lubricant oil to form new particles. These new particles are an important source of ultrafine particles in the areas nearby large airports. The ambient measurements were performed downwind of Frankfurt International Airport, and it was found that the fraction of lubricant oil is largest in the smallest particles. In the laboratory, the main finding was that evaporated lubricant oil nucleates and forms new particles rapidly. The results suggest that nucleation of lubricant oil and subsequent particle growth can occur in the cooling exhaust plumes of aircraft-turbofans.
The fourth manuscript (Wang et al., 2022) is a new particle formation study in the CLOUD chamber at CERN. This study shows that nitric acid, sulfuric acid, and ammonia interact synergistically and rapidly form particles under upper free tropospheric conditions. These particles can grow by condensation (driven by the availability of ammonia) up to CCN sizes and INP particles. The ability of these particles to act as a CCN and INP was also investigated and it was found to be as efficient as for desert dust. This mechanism constitutes an important finding and it can account for previous observations of high concentrations of ammonia and ammonium nitrate over the Asia monsoon region.
Forests are important components of the greenhouse gas balance of Europe. There is considerable uncertainty about how predicted changes to climate and nitrogen deposition will perturb the carbon and nitrogen cycles of European forests and thereby alter forest growth, carbon sequestration and N2O emission. The present study aimed to quantify the carbon and nitrogen balance, including the exchange of greenhouse gases, of European forests over the period 2010–2030, with a particular emphasis on the spatial variability of change. The analysis was carried out for two tree species: European beech and Scots pine. For this purpose, four different dynamic models were used: BASFOR, DailyDayCent, INTEGRATOR and Landscape-DNDC. These models span a range from semi-empirical to complex mechanistic. Comparison of these models allowed assessment of the extent to which model predictions depended on differences in model inputs and structure. We found a European average carbon sink of 0.160 ± 0.020 kgC m−2 yr−1 (pine) and 0.138 ± 0.062 kgC m−2 yr−1 (beech) and N2O source of 0.285 ± 0.125 kgN ha−1 yr−1 (pine) and 0.575 ± 0.105 kgN ha−1 yr−1 (beech). The European average greenhouse gas potential of the carbon source was 18 (pine) and 8 (beech) times that of the N2O source. Carbon sequestration was larger in the trees than in the soil. Carbon sequestration and forest growth were largest in central Europe and lowest in northern Sweden and Finland, N. Poland and S. Spain. No single driver was found to dominate change across Europe. Forests were found to be most sensitive to change in environmental drivers where the drivers were limiting growth, where changes were particularly large or where changes acted in concert. The models disagreed as to which environmental changes were most significant for the geographical variation in forest growth and as to which tree species showed the largest rate of carbon sequestration. Pine and beech forests were found to have differing sensitivities to environmental change, in particular the response to changes in nitrogen and precipitation, with beech forest more vulnerable to drought. There was considerable uncertainty about the geographical location of N2O emissions. Two of the models BASFOR and LandscapeDNDC had largest emissions in central Europe where nitrogen deposition and soil nitrogen were largest whereas the two other models identified different regions with large N2O emission. N2O emissions were found to be larger from beech than pine forests and were found to be particularly sensitive to forest growth.
Environmental change impacts on the C- and N-cycle of European forests: a model comparison study
(2013)
Forests are important components of the greenhouse gas balance of Europe. There is considerable uncertainty about how predicted changes to climate and nitrogen deposition will perturb the carbon and nitrogen cycles of European forests and thereby alter forest growth, carbon sequestration and N2O emission. The present study aimed to quantify the carbon and nitrogen balance, including the exchange of greenhouse gases, of European forests over the period 2010–2030, with a particular emphasis on the spatial variability of change. The analysis was carried out for two tree species: European beech and Scots pine. For this purpose, four different dynamic models were used: BASFOR, DailyDayCent, INTEGRATOR and Landscape-DNDC. These models span a range from semi-empirical to complex mechanistic. Comparison of these models allowed assessment of the extent to which model predictions depended on differences in model inputs and structure. We found a European average carbon sink of 0.160 ± 0.020 kgC m−2 yr−1 (pine) and 0.138 ± 0.062 kgC m−2 yr−1 (beech) and N2O source of 0.285 ± 0.125 kgN ha−1 yr−1 (pine) and 0.575 ± 0.105 kgN ha−1 yr−1 (beech). The European average greenhouse gas potential of the carbon sink was 18 (pine) and 8 (beech) times that of the N2O source. Carbon sequestration was larger in the trees than in the soil. Carbon sequestration and forest growth were largest in central Europe and lowest in northern Sweden and Finland, N. Poland and S. Spain. No single driver was found to dominate change across Europe. Forests were found to be most sensitive to change in environmental drivers where the drivers were limiting growth, where changes were particularly large or where changes acted in concert. The models disagreed as to which environmental changes were most significant for the geographical variation in forest growth and as to which tree species showed the largest rate of carbon sequestration. Pine and beech forests were found to have differing sensitivities to environmental change, in particular the response to changes in nitrogen and precipitation, with beech forest more vulnerable to drought. There was considerable uncertainty about the geographical location of N2O emissions. Two of the models BASFOR and LandscapeDNDC had largest emissions in central Europe where nitrogen deposition and soil nitrogen were largest, whereas the two other models identified different regions with large N2O emission. N2O emissions were found to be larger from beech than pine forests and were found to be particularly sensitive to forest growth.
During the APE-THESEO mission in the Indian Ocean the Myasishchev Design Bureau stratospheric research aircraft M55 Geophysica performed a flight over and within the inner core region of tropical cyclone Davina. Measurements of total water, water vapour, temperature, aerosol backscattering, ozone and tracers were made and are discussed here in comparison with the averages of those quantities acquired during the campaign time frame.
Temperature anomalies in the tropical tropopause layer (TTL), warmer than average in the lower part and colder than average in the upper TTL were observed. Ozone was strongly reduced compared to its average value, and thick cirrus decks were present up to the cold point, sometimes topped by a layer of very dry air. Evidence for meridional transport of trace gases in the stratosphere above the cyclone and the perturbed water distribution in the TTL is illustrated and discussed.
During the APE-THESEO mission in the Indian Ocean the Myasishchev Design Bureau stratospheric research aircraft M55 Geophysica performed a flight over and within the inner core region of tropical cyclone Davina. Measurements of total water, water vapour, temperature, aerosol backscattering, ozone and tracers were made and are discussed here in comparison with the averages of those quantities acquired during the campaign time frame. Temperature anomalies in the tropical tropopause layer (TTL), warmer than average in the lower part and colder than average in the upper TTL were observed. Ozone was strongly reduced compared to its average value, and thick cirrus decks were present up to the cold point, sometimes topped by a layer of very dry air. Evidence for meridional transport of trace gases in the stratosphere above the cyclone was observed and perturbed water distribution in the TTL was documented. The paper discuss possible processes of dehydration induced by the cirrus forming above the cyclone, and change in the chemical tracer and water distribution in the lower stratosphere 400–430 K due to meridional transport from the mid-latitudes and link with Davina. Moreover it compares the data prior and after the cyclone passage to discuss its actual impact on the atmospheric chemistry and thermodynamics.
Meteorologie
(2016)
Die Wetterkunde setzt sich aus vier Tätigkeitsfeldern zusammen: Datensammlung, Modellentwicklung, Prognostik und Wettersteuerung. Die Vorhersage zukünftiger Wetterereignisse stellt mithin nur eines von mehreren Aufgabengebieten dar. In ihrer Geschichte verlief die Entwicklung der vier Felder lange Zeit weitgehend separat. In den Agrar- und Seefahrergesellschaften der Antike führten Stadtverwaltungen und Tempel kalendarische Aufzeichnungen über alle Arten von Himmelsereignissen. Kosmologische Modelle wurden in der Naturphilosophie entworfen. Aristoteles unterschied dabei den Gegenstandbereich der 'Uranologie', die sich mit feststehenden Körpern wie Fixsternen und sich regelmäßig bewegenden Körpern wie Planeten beschäftigt, von dem der 'Meteorologie', die es mit singulären oder unregelmäßigen Ereignissen wie den Witterungserscheinungen zu tun hat. Für Prognosen in diesem Bereich stützte man sich auf Erfahrungswerte und ein Denken in Wenn-dann-Strukturen: Das Auftreten oder Ausbleiben von Himmelsphänomenen oder ihrer Kombination und das Verhalten von Pflanzen und Tieren zu bestimmten Tageszeiten wurde als Anzeichen für zukünftige Wetterereignisse gedeutet. Dieses Wissen bezog sich allein auf die alltägliche Nutzanwendung und war nicht an Erklärungen interessiert. In der Antike muss deshalb nicht die Meteorologie, sondern die Wetterprophetie als das wetterkundliche Zukunftswissen gelten. Die Mittel zur Beeinflussung des Wetters schließlich bestanden in Zaubern und Gebeten.1 An dieser Trennung der verschiedenen Tätigkeitsfelder der Wetterkunde änderte sich im Mittelalter und in der frühen Neuzeit kaum etwas.
The complete elastic stiffness tensor of thiourea has been determined from thermal diffuse scattering (TDS) using high-energy photons (100 keV). Comparison with earlier data confirms a very good agreement of the tensor coefficients. In contrast with established methods to obtain elastic stiffness coefficients (e.g. Brillouin spectroscopy, inelastic X-ray or neutron scattering, ultrasound spectroscopy), their determination from TDS is faster, does not require large samples or intricate sample preparation, and is applicable to opaque crystals. Using high-energy photons extends the applicability of the TDS-based approach to organic compounds which would suffer from radiation damage at lower photon energies.
The seasonality of transport and mixing of air into the lowermost stratosphere (LMS) is studied using distributions of mean age of air and a~mass balance approach, based on in-situ observations of SF6 and CO2 during the SPURT (Spurenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region) aircraft campaigns. Combining the information of the mean age of air and the water vapour distributions we demonstrate that the tropospheric air transported into the LMS above the extratropical tropopause layer (ExTL) originates predominantly from the tropical tropopause layer (TTL). The concept of our mass balance is based on simultaneous measurements of the two passive tracers and the assumption that transport into the LMS can be described by age spectra which are superposition of two different modes. Based on this concept we conclude that the stratospheric influence on LMS composition is strongest in April with tropospheric fractions (α1) below 20% and that the strongest tropospheric signatures are found in October with (α1 greater than 80%. Beyond the fractions, our mass balance concept allows to calculate the associated transit times for transport of tropospheric air from the tropics into the LMS. The shortest transit times (<0.3 years) are derived for the summer, continuously increasing up to 0.8 years by the end of spring. These findings suggest that strong quasi-horizontal mixing across the weak subtropical jet from summer to mid of autumn and the considerably shorter residual transport time-scales within the lower branch of the Brewer-Dobson circulation in summer than in winter dominates the tropospheric influence in the LMS until the beginning of next year's summer.
The seasonality of transport and mixing of air into the lowermost stratosphere (LMS) is studied using distributions of mean age of air and a mass balance approach, based on in-situ observations of SF6 and CO2 during the SPURT (Spurenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region) aircraft campaigns. Combining the information of the mean age of air and the water vapour distributions we demonstrate that the tropospheric air transported into the LMS above the extratropical tropopause layer (ExTL) originates predominantly from the tropical tropopause layer (TTL). The concept of our mass balance is based on simultaneous measurements of the two passive tracers and the assumption that transport into the LMS can be described by age spectra which are superposition of two different modes. Based on this concept we conclude that the stratospheric influence on LMS composition is strongest in April with extreme values of the tropospheric fractions (alpha1) below 20% and that the strongest tropospheric signatures are found in October with alpha1 greater than 80%. Beyond the fractions, our mass balance concept allows us to calculate the associated transit times for transport of tropospheric air from the tropics into the LMS. The shortest transit times (<0.3 years) are derived for the summer, continuously increasing up to 0.8 years by the end of spring. These findings suggest that strong quasi-horizontal mixing across the weak subtropical jet from summer to mid of autumn and the considerably shorter residual transport time-scales within the lower branch of the Brewer-Dobson circulation in summer than in winter dominates the tropospheric influence in the LMS until the beginning of next year's summer.
In this paper we present evidence that the observed increase in tropical upwelling after the year 2000 may be attributed to a change in the Brewer-Dobson circulation pattern. For this purpose, we use the concept of transit times derived from residual circulation trajectories and different in-situ measurements of ozone and nitrous dioxide. Observations from the Canadian midlatitude ozone profile record, probability density functions of in-situ N2O observations and a shift of the N2O-O3 correlation slopes, taken together, indicate that the increased upwelling in the tropics after the year 2000 appears to have triggered an intensification of tracer transport from the tropics into the extratropics in the lower stratosphere below about 500 K. This finding is corroborated by the fact that transit times along the shallow branch of the residual circulation into the LMS have decreased for the same time period (1993–2003). On a longer time scale (1979–2009), the transit time of the shallow residual circulation branch show a steady decrease of about −1 month/decade over the last 30 years, while the transit times of the deep branch remain unchanged. This highlights the fact that a change in the upwelling across the tropical tropopause is not a direct indicator for changes of the whole Brewer-Dobson circulation.
In this paper we present evidence that the observed increase in tropical upwelling after the year 2000 may be attributed to a change in the Brewer-Dobson circulation pattern. For this purpose, we use the concept of transit times derived from residual circulation trajectories and different in-situ measurements of ozone and nitrous dioxide. Observations from the Canadian midlatitude ozone profile record, probability density functions of in-situ N2O observations and a shift of the N2O-O3 correlation slopes, taken together, indicate that the increased upwelling in the tropics after the year 2000 appears to have triggered an intensification of tracer transport from the tropics into the extratropics in the lower stratosphere below about 500 K. This finding is corroborated by the fact that transit times along the shallow branch of the residual circulation into the LMS have decreased for the same time period (1993–2003). On a longer time scale (1979–2009), the transit time of the shallow residual circulation branch show a steady decrease of about −1 month/decade over the last 30 yr, while the transit times of the deep branch remain unchanged. This highlights that changes in the upwelling across the tropical tropopause are not sufficient as an indicator for changes in the entire Brewer-Dobson circulation.
Im Rahmen des Projektes SPURT (Spurenstofftransport in der Tropopausenregion) als Teil des deutschen Atmosphärenforschungsprogramms AFO 2000 wurden bei 8 Messkampagnen mit insgesamt 36 Flügen innerhalb eines Beobachtungszeitraums von zwei Jahren (Nov. 2001 bis Juli 2003) Spurengasmessungen in dem Breitenbereich zwischen 35°N und 75°N durchgeführt. Für die Messungen der Spurengase N2O, F12, SF6, H2 und CO wurde der vollautomatisierte in-situ GC (Gaschromatograph) GhOST II (Gas Chromatograph for the Observation of Stratospheric Tracers) entwickelt und eingesetzt. Das Ziel dieser Messungen war die Untersuchung der jahreszeitlichen Variabilität der Spurengase in der oberen Troposphäre und untersten Stratosphäre (UT/LMS: Upper Troposphere/Lowermost Stratosphere), um die Transport- und Austauschprozesse in der Tropopausenregion besser zu verstehen. Zur Untersuchung von Transport und Mischung in der UT/LMS wurden die Rückwärtstrajektorien entlang der Flugpfade, die Verteilungen der Tracer N2O, F12, SF6, CO und CO2 (MPI für Chemie in Mainz), die Tracer/Tracer-Korrelationen N2O/F12, N2O/O3 F12/O3 und SF6/O3 und die Verteilungen des aus SF6-Messungen berechnete mittlere Alters der Luft herangezogen. Zusätzlich wurden die simultanen Messungen der beiden Alterstracer CO2 und SF6 genutzt, um die Propagation der Amplitude des troposphärischen CO2-Jahresgangs in die LMS zu bestimmen und daraus mit Hilfe eines empirischen Altersspektrums den Eintrag und die mittlere Transportzeit aus der Troposphäre in die unterste Stratosphäre zu quantifizieren. Grundsätzlich muss die LMS in zwei Bereiche eingeteilt werden – die Übergangsschicht („tropopause following layer“) bis etwa 20-30 K über der potentiellen Temperatur der lokalen Tropopause [Hoor et al., 2004] und die freie LMS oberhalb dieser Schicht. Als wesentliche Unterscheidungsmerkmale beider Bereiche wird die mittlere Transportzeit des Eintrags troposphärischer Luft identifiziert. Aus Trajektorienuntersuchungen und Tracerverteilungen (Kap. 3.4) kann gezeigt werden, dass der Transport in die Übergangsschicht und die Mischungsprozesse in diesem Bereich auf der Zeitskala der mesoskaligen troposphärischen Prozesse ablaufen. Im Gegensatz dazu werden aus der Massenbilanz (Kap. 5.3) mittlere Transportzeiten aus der Troposphäre in die freie LMS von einigen Wochen bis zu mehreren Monaten abgeleitet. Außerdem konnte nachgewiesen werden, dass der troposphärische Eintrag in der freien LMS fast ausschließlich auf quasihorizontale isentrope Einmischung aus den Tropen über die Transportbarriere des Subtropenjets zurückzuführen ist. Nur im Sommer und Herbst konnte auch oberhalb der Übergangsschicht für einzelne Messungen ein Einfluss aus der extratropischen Troposphäre beobachtet werden. Die in dieser Arbeit untersuchten Tracerverteilungen und -korrelationen (Kap. 4) und die Verteilung des mittleren Alters (Kap.5.2) in der LMS zeigen einen Jahresgang mit einem maximalen troposphärischen Einfluss im Oktober und einem maximalen stratosphärischen Einfluss im April. Diese saisonale Charakteristik in der freien LMS kann durch die saisonalen Änderungen des Verhältnisses von Abwärtstransport aus der Overworld und quasihorizontalem Transport aus den Tropen und durch die mit den jeweiligen Transportprozessen assoziierte mittlere Transportzeiten erklärt werden, die aus Massenbilanzrechnungen bestimmt wurden. Es wird gezeigt, dass der überwiegende Eintrag von troposphärischer Luft in die LMS im Sommer und Herbst stattfindet, wobei im Mittel die kürzesten mittleren Transitzeiten (unter 0.3 Jahre) für den August und die längsten Transitzeiten (über 0.6 Jahre) für den Mai berechnet werden. Aus den Ergebnissen wird gefolgert, dass ein ausgeprägter isentroper Austauschprozess über den Subtropenjet im Sommer bis in den Herbst hinein der dominierende troposphärische Einfluss in der LMS bis in den Mai ist. Der Vergleich zwischen SPURT und anderen in der UT/LMS im Zeitraum von 1992 bis 1998 durchgeführten Messkampagnen zeigt einen systematischen Unterschied in den N2O/O3-Korrelationen. Die Zunahme von O3 relativ zu N2O in der LMS ist um etwa 6.5 ppb O3 pro 1 ppb N2O bzw. etwa 40% größer als die Zunahme bei jahreszeitlich vergleichbaren früheren Kampagnen. Durch eine weitergehende Analyse der Messungen, z.B. durch den Vergleich der N2O-Verteilungen in der LMS bei verschiedenen Messkampagnen, und zusätzlichen Informationen aus Satelliten- und Ballonmessungen wird abgeleitet, dass diese Änderung der N2O/O3-Korrelationen im Wesentlichen auf einen im Zeitraum von SPURT stärkeren quasihorizontalen Transport aus den Tropen in die Extratropen im Bereich des so genannten „tropical controlled transition layer“ [Rosenlof et al., 1997] zwischen 16-21 km (bzw. Θ ≈ 380-450 K) zurückzuführen ist. In Kooperation mit B. Bregman wurden mit dem Chemie-Transport-Modell TM5 des KNMI die Verteilungen von SF6 und CO2 in der Troposphäre und Stratosphäre, unter den Zielsetzungen Evaluation des Modelltransports und Erweiterung des Datensatzes von SPURT auf globalen Maßstab, für den Zeitraum 1.1.2000 bis 31.12.2002 modelliert. Dabei konnte gezeigt werden, dass bei Modellstudien zur Evaluation des Transports mit Hilfe von Alterstracern nicht nur troposphärisch monoton steigende Tracer wie SF6 sondern auch saisonal variable Tracer wie CO2 verwendet werden müssen. Bei dem Vergleich der Modellergebnisse des TM5 mit ER2- und SPURTMessungen zeigt sich, dass das Modell zum jetzigen Zeitpunkt in der Lage ist, das mittlere Alter in der unteren Stratosphäre und die SF6- und CO2-Verteilungen in der LMS qualitativ richtig wiederzugeben. Das mittlere Alter in der unteren Stratosphäre wird um etwa 0.5 bis 1 Jahr in den Tropen über- und in den Extratropen unterschätzt. Die vertikalen Gradienten im Modell für SF6 und CO2 in der LMS sind, insbesondere im Winter und Frühjahr, zu gering. Die Amplitude des CO2-Jahresganges in der oberen Troposphäre und in der LMS wird durch das Modell unterschätzt, während der saisonale Verlauf des Jahresganges richtig wiedergegeben wird. Im Moment wird vermutet, dass eine zu starke isentrope Mischung zwischen Tropen und Extratropen und/oder ein zu geringer Aufwärtstransport in der extratropischen Troposphäre im Sommer und Herbst die Ursachen für die beobachteten Abweichungen zwischen Modell und Messung sind.
Am 27. Januar 1981 verstarb an den Folgen eines tragischen Verkehrsunfalls das Ehrenmitglied des Naturwissenschaftlichen Vereins Osnabrück, Prof. Dr. GERHARD KELLER aus Ibbenbüren in seinem 77. Lebensjahr. Der Naturwissenschaftliche Verein Osnabrück gedenkt des Geologen und Naturwissenschaftlers GERHARD KELLER in seinem weit gespannten wissenschaftlichen Wirkungskreis und der besonderen Hinwendung zur Geologie seiner näheren Heimat, dem Osnabrücker Bergland und Teutoburger Wald.
This thesis is focusing on the impact of Paratethys and Mediterranean water bodies over the Eurasian climate and the interplay between climate, tectonics and biosphere during the late Miocene. This target was the interval between 12.7 and 7.65 Ma for Paratethys, following the Eastern Paratethys restriction and isolation, and 7.2−6.5 Ma (the early Messinian) in Mediterranean, zooming on the effects of gateway restrictions over the eastern Mediterranean and the new born Aegean domain. In both cases restriction is overlapping with large scale climatic changes and tectonic reconfiguration, leading a sort of symbiotic relationship.
Paratethys was a giant epicontinental sea that covered a large part of Eurasia since Paleogene. Due to the Eurasia-Afro-Arabia collision and formation of the Alpine-Himalayan belt (Rögl, 1999; Popov et al., 2006), the Paratethys was divided during the late Miocene in smaller basins that in time were isolated of each other. The protracted isolation and intense continentalisation of paratethyan realm led to changes in humidity distribution, basin connectivity, sediment sources and salinity. These changes had in turn major consequences over water circulation, water availability, vegetation cover and biota. These changes are more intense after 11.6 Ma, when the Eastern Paratethys lost any sustained marine connection, evolving into an enclosed system with endemic fauna (Harzhauser and Piller, 2007).
Mediterranean Sea is a Mezozoic oceanic relic squeezed between Africa, Europe, Anatolia and Arabia, as Africa continued to subduct beneath the European plate. As opposed to Paratethys, it maintained the open connection with the ocean until Messinian, when the two Atlantic gateways (Betic and Rifian corridors) closed for a short time, isolating the basin. The cut off resulted in a dramatic drop down and onset of evaporitic precipitation in marginal basins, the event receiving the name of Messinian Salinity Crisis (5.97−5.55). The restriction affected all marine ecosystems, due to changes in salinity and stratification of water column.
The main objectives of this thesis were:
(1) build valid paleo-temperatures records for both basins based on biomarkers;
(2) reconstruct the hydrology for the late Miocene time interval;
(3) identify vegetation composition and changes;
(4) identify paleo-fires in the late Miocene sediment records;
(5) identify the biotic response to the overall climate and tectonic changes.
All the above objectives were attained with results published in specific journals (Chapters 5−7).
Based on Panagia section (Taman Peninsula, Russia) the longest Paratethys temperature record was completed (~5 Myr), covering the interval between 12.7 and 7.65 Ma. A comprehensive SST and MAT records was obtained, as well as soil pH and carbon (δ13C) and hydrogen (δ2H) stable isotopic compositions on n-alkanes and alkenones. The main findings are concentrated around three prolonged periods with severe droughts affecting the late Miocene circum-Paratethys region peaking at 9.65, 9.4 and 7.9 Ma, associated with a transition towards open land vegetation, intensification of fire activity and enhanced evaporation and aridity.
The time intervals with dryer conditions recorded in Panagia coincide with periods of mammal turnover and dispersal in Eurasia indicating that major environmental changes occurred in the circum-Paratethys region and Paratethys fragmentation had a great impact on the terrestrial ecosystems, when periods of prolonged droughts generated biotic crises and animal displacements across the Eurasian continent. The δ13CC29n-alkane values and charcoal morphologies from Panagia indicate an increased contribution of C4 plants adapted to drier conditions at 9.66 Ma. Similarly high δ13CC29n-alkane values continue until 9.4 Ma, when in Western Europe increased seasonality accelerated the demise of the evergreen subtropical woodlands and expansion of grasslands from Anatolia and Middle East to Europe.
As a result of basin fragmentation and climatic stress, the Eastern Paratethys sub-basins progressively lost their marine properties and turned into brackish-fresh water bodies fed primarily by riverine input. The shallower areas became in time emerged, obstructing connections and isolating the biota, inducing rapid adjusting or extinctions. Thus, the Paratethys harbored a highly endemic fauna (Rögl, 1999), such as dwarf whales, dolphins, seals (among mammals), as well as fish and other taxa (mollusks, ostracods, diatoms, foraminifera, algae, etc.).
Collectively the data structured and analyzed in chapter five support a model in which the Eastern Paratethys evolved as a largely (en)closed system, registering paleoenvironmental signals that are governed by interbasinal connectivity (or lack of it) and regional climate changes in the basin catchment. Acting as an important source of humidity for Western and Central Asia, the size and areal extent of the Paratethys water body is likely to have had a major impact on hydroclimate patterns in the Eurasian interior, with the cumulative fluctuations in both hydrology and surface temperature enhancing the aridity and seasonality, with different partition of moisture over the year. Our combined data suggests a decoupling of Paratethys from the global system as isolation advanced, dominated by regional tectonics and ultimately the Paratethys volume and areal extent reduction.
Der oder das (noch nicht im letzten Rechtschreibduden verzeichnete) "Geotop" ist ein erhaltens- und schutzwürdiges Objekt der geologischen Erdgeschichte bzw. "Geotope" sind erdgeschichtliche Bildungen der unbelebten Natur, die Erkenntnisse über die Entwicklung der Erde oder des Lebens vermitteln. Sie umfassen Aufschlüsse von Gesteinen, Böden, Mineralen und Fossilien sowie einzelne Naturschöpfungen oder natürliche Landschaftsteile" (S.ll).
Diamant hat besondere physikalische und optische Eigenschaften sowie eine starke Resistenz gegenüber Strahlenschädigung. Diese Eigenschaften ermöglichen eine vielfältige Anwendung von Diamant in Wissenschaft und Technik, wie zum Beispiel als Sensormaterial in Strahlungsdetektoren.
Kubisches Zirconiumdioxid (ZrO2) wird aufgrund seiner mechanisch und optisch ähnlichen Eigenschaften unter anderem an Stelle von Diamant eingesetzt. Es ist ebenfalls ein geeignetes Material für viele technische Anwendungen und wird durch seine Strahlenresistenz in Strahlungsumgebungen verwendet. Da beide Materialien in diesem Anwendungsbereich hoher energetischer Strahlung ausgesetzt sind, sind Reaktionen auf die Bestrahlung wie etwa strukturelle Veränderungen oder die Änderungen von Materialeigenschaften von großem Interesse.
In der vorliegenden Arbeit wurde die Morphologie, Struktur und physikalischen Eigenschaften von Diamant und Yttriumoxid-stabilisiertem kubischem ZrO2 nach der Bestrahlung mit 14 MeV Au-Ionen und 1.6 GeV Au-Ionen untersucht. Die durch die Bestrahlung verursachten Veränderungen der Oberflächen und der bestrahlten Volumina wurden mit diversen komplementären analytischen Methoden charakterisiert, bewertet und für die verschiedenen Materialien und Ionenenergien verglichen.
Mittels Röntgenfluoreszenzmessungen wurde die Verteilung und Menge an implantiertem Au semi-quantitativ ermittelt. Die Oberflächen der Proben wurden mit optischer Mikroskopie, Rasterkraftmikroskopie, Rasterelektronenmikroskopie, Röntgenreflektometrie und Elektronenrückstreubeugung untersucht. Strukturelle Veränderungen wurden mit Raman-Spektroskopie analysiert. Der elektrische Widerstand, die Dichte, die Härte sowie das Ätzverhalten der bestrahlten Proben wurden ermittelt und geben Auskunft über die Änderung physikalischer Eigenschaften der Materialien.
Diamant und kubisches ZrO2 reagieren sehr unterschiedlich auf die Bestrahlung mit Au-Ionen gleicher Energien und Fluenzen. Die Diamantproben zeigen nach der Bestrahlung mit 14 MeV Au-Ionen deutliche Veränderungen und Schädigungen der Oberfläche sowie des bestrahlten Volumens. Es wird eine Änderung der Struktur, der Dichte, der Härte, des elektrischen Widerstands sowie des Ätzverhaltens der Proben beobachtet, was auf die Amorphisierung von Diamant zurückgeführt wird. Kubisches ZrO2 ist deutlich strahlungsresistenter gegenüber der Bestrahlung mit 14 MeV Au-Ionen. Es werden keine signifikanten strukturellen Änderungen im getesteten Fluenzbereich beobachtet.
Die mit 1.6 GeV Au-Ionen bestrahlten Diamanten zeigen nur geringe Schädigungen und keine deutliche Änderung der Struktur oder der physikalischen Eigenschaften. Die kubischen ZrO2 Proben sind als Folge der Bestrahlung mit 1.6 GeV Au-Ionen zerbrochen, was auf hohe interne Spannung durch Defektbildung zurückgeführt wird.
Development of a Bioaerosol single particle detector (BIO IN) for the Fast Ice Nucleus CHamber FINCH
(2010)
In this work we present the setup and first tests of our new BIO IN detector. This detector was constructed to classify atmospheric ice nuclei (IN) for their biological content. It is designed to be coupled to the Fast Ice Nucleus CHamber FINCH. If one particle acts as an ice nucleus, it will be at least partly covered with ice at the end of the development section of the FINCH chamber. The device combines an auto-fluorescence detector and a circular depolarization detector for simultaneous detection of biological material and discrimination between water droplets, ice crystals and non activated large aerosol particles. The excitation of biological material with UV light and analysis of auto-fluorescence is a common principle used for flow cytometry, fluorescence microscopy, spectroscopy and imaging. The detection of auto-fluorescence of airborne single particles demands some more experimental effort. However, expensive commercial sensors are available for special purposes, e.g. size distribution measurements. But these sensors will not fit the specifications needed for the FINCH IN counter (e.g. high sample flow of up 10 LPM). The newly developed -low cost- BIO IN sensor uses a single high-power UV LED for the electronic excitation instead of much more expensive UV lasers. Other key advantages of the new sensor are the low weight, compact size, and the little effect on the aerosol sample, which allows it to be coupled with other instruments for further analysis. The instrument will be flown on one of the first missions of the new German research aircraft "HALO" (High Altitude and LOng range).
In this work we present the setup and first tests of our new BIO IN detector. This detector is designed to classify atmospheric ice nuclei (IN) for their biological content. Biological material is identified via its auto-fluorescence (intrinsic fluorescence) after irradiation with UV radiation. Ice nuclei are key substances for precipitation development via the Bergeron–Findeisen process. The level of scientific knowledge regarding origin and climatology (temporal and spatial distribution) of IN is very low. Some biological material is known to be active as IN even at relatively high temperatures of up to –2°C (e.g. pseudomonas syringae bacteria). These biological IN could have a strong influence on the formation of clouds and precipitation. We have designed the new BIO IN sensor to analyze the abundance of IN of biological origin. The instrument will be flown on one of the first missions of the new German research aircraft ''HALO'' (High Altitude and LOng Range).
Das Ziel dieser Arbeit wurde eingangs über den Begriff der erweiterten Schließung der optischen und mikrophysikalischen Eigenschaften der Partikel definiert. Hierunter versteht man das Zusammenfügen von verschiedenen Messungen zu einem konsistenten Bild der betrachteten Partikeleigenschaften. Darüber hinaus sollen die Messungen auch in anderen Teilgebieten der Aerosolphysik verwendbar sein, um so das konsistente Bild zu erweitern. Dieses so umschriebene Ziel konnte für die mikrophysikalischen und optischen Messergebnisse, die während des LACE 98 Experimentes, einem vom Bundesministerium für Forschung und Bildung (Bmb f) geförderten Schließungsexperiment, in Lindenberg (Brandenburg) rund 50 km südöstlich von Berlin im Juli und August 1998 erfasst wurden, erreicht werden. Die Messungen wurden erfolgreich zu einem konsistenten Datensatz und einem "Bild" der Partikeleigenschaften zusammengefügt. Unter dem Begriff "Bild" subsummiert sich hierbei nicht nur eine Charakterisierung der Variabilität und Abhängigkeit der Partikeleigenschaften, z.B. von der rel. Luftfeuchte, sondern darüber hinaus auch eine Charakterisierung der Beeinflussung verschiedener von den Eigenschaften der Partikel abhängiger Größen. Hierzu zählen Strahlungshaushaltsgrößen (Erwärmungsrate der Luft durch Absorption solarer Strahlung und die Volumenabsorption solarer Strahlung durch Partikel), wolkenphysikalische Größen (maximale Übersättigung der Wolkenluft während der Wolkenentstehung und Anzahlkonzentration der wachsenden Wolkentropfen), die massengewichtete mittlere Sedimentationsgeschwindigkeit von Partikeln und nicht zuletzt gesundheitsrelevante Größen, wie z.B. die vom Menschen beim Atmen aufgenommene und eingelagerte Partikelmasse. Nachfolgende Zusammenstellung soll nochmals die erzielten Ergebnisse zusammenfassen. Für eine detaillierte Darstellung der in den einzelnen Kapiteln erzielten Ergebnisse soll hier nur auf die jeweiligen Zusammenfassungen der einzelnen Kapitel verwiesen werden. . Im Rahmen der direkten Schließung, wurden unterschiedliche Verfahren zur Bestimmung der optischen Eigenschaften der Partikel erfolgreich miteinander verglichen. Beteiligt waren bei diesem Vergleich folgende Methoden: Partikel im trockenen Zustand: -- Aerosolphotometer (alle optischen Eigenschaften, ) -- Nephelometer (Streukoeffizient) -- PSAP (Absorptionskoeffizient) -- IPMethode (Absorptionskoeffizient) -- Telephotometer (Extinktionskoeffizient) Partikel bei Umgebungsfeuchte: -- Telephotometer (Extinktionskoeffizient) -- horizontales Lidar (Extinktionskoeffizient) Es zeigte sich, dass sich das Aerosolphotometer mit seinem schon aus der Theorie des Messverfahrens her begründeten konsistenten Satz aller optischen Eigenschaften als Referenzmethode während LACE 98 bewährte. Mit seiner Hilfe konnte nun auch die Gültigkeit einer empirischen Korrektur des PSAP nach Bond et al. [1999] für natürliche Aerosolpartikel bestätigt werden. Dem Anwender dieses Gerätes, das mit einer hervorragenden zeitlichen Auflösung von wenigen Minuten den Absorptionskoeffizienten bestimmt, stehen somit zwei unabhängig voneinander gewonnene Kalibrierungsfunktionen zur Verfügung, die innerhalb der Fehlergrenzen auch mit einander im Einklang stehen. . Im Rahmen der indirekten Schließung wurde ein Modell entwickelt, mit dem auf Basis eines Kugelschalenmodells der Partikel aus Messungen der mikrophysikalischen Eigenschaften der Partikel den Extinktions, den Streu- und den Absorptionskoeffizienten sowie die Single Scattering Albedo berechnet wurden. Mit Hilfe dieses Modells wurde der Feuchteeffekt der oben genannten optischen Eigenschaften berechnet. Mit diesen Ergebnissen konnten dann die Messwerte des Telephotometers feuchtekorrigiert, und mit den Messungen des Aerosolphotometers verglichen werden, wo bei eine gute Übereinstimmung der Messreihen festgestellt werden konnte. Die beobachteten Unterschiede konnten auf Ernteaktivitäten, die nur die Messungen des Telephotometers beeinflussten, zurückgeführt werden. Ein Vergleich der mit Hilfe des Modells auch direkt berechenbaren optischen Eigenschaften mit den direkten Messwerten der beteiligten Verfahren fiel ebenfalls positiv aus. Anhand aller Modellrechnungen wurde eine physikalisch motivierte Näherungsfunktion für den Feuchteeffekt des Extinktions- und des Streukoeffizienten als Funktion des Aktivierungsparameters bereit gestellt. In Klimamodellen kann mit Hilfe der vorgestellten Näherungsfunktionen der Feuchteeffekt auf einfache Weise parametrisiert werden. Wenn man allerdings konkrete Messergebnisse miteinander vergleichen möchte, ist man auf eine vollständige Erfassung der mikrophysikalischen Eigenschaften der Partikel angewiesen. . Im Teil IV der Arbeit wurden auf der Basis des zuvor vorgestellten Datensatzes und der hierfür entwickelten Verfahren (Algorithmen) weitere Auswertungen zu unterschiedlichen, für die Meteorologie interessanten Themengebieten, vorgestellt und ihre Ergebnisse charakterisiert. . In Kapitel 6.1 wurde mit Hilfe von Auswertegleichungen aus den in dieser Arbeit erstellten Messungen des Sieben-Sensor-Bilanzphotometers und den Messungen des Aerosolphotometers die Volumenabsorptionsrate solarer Strahlung der bodennahen Partikel und die daraus resultierende Erwärmungsrate der Luft berechnet. Die Ergebnisse wurden mit Literaturwerten anderer Messkampagnen verglichen. Insbesondere konnte ein interessantes Ergebnis von Hänel
Soil water potential is crucial to plant transpiration and thus to carbon cycling and biosphere–atmosphere interactions, yet it is difficult to measure in the field. Volumetric and gravimetric water contents are easy and cheap to measure in the field, but can be a poor proxy of plant-available water. Soil water content can be transformed to water potential using soil moisture retention curves. We provide empirically derived soil moisture retention curves for seven soil types in the Kruger National Park, South Africa. Site-specific curves produced excellent estimates of soil water potential from soil water content values. Curves from soils derived from the same geological substrate were similar, potentially allowing for the use of one curve for basalt soils and another for granite soils. It is anticipated that this dataset will help hydrologists and ecophysiologists understand water dynamics, carbon cycling and biosphere–atmosphere interactions under current and changing climatic conditions in the region.
The timing and duration of leaf deployment strongly regulate earth-atmosphere interactions and biotic processes. Leaf dynamics therefore have major implications for life on earth, including the global energy balance, carbon and water cycles, feedbacks to climate, species extinction risk and agriculture. Evidence of shifts in the timing of leaf deployment and senescence (leaf phenology) as a result of climate change has been accumulating over the past decades, particularly in relation to spring phenology in the northern hemisphere. However, leaf phenological change in other parts of the world has received less attention. This thesis quantifies global phenological change over the past three decades using remotely sensed data. Phenological change was found to be widespread and severe, also in the southern hemisphere. While the detected change testifies of the phenological plasticity of many plant species, it is not clear if the duration of leaf deployment (leaf habit) is equally sensitive to environmental change. Since evergreen and deciduous leaf habits are often distinctly sorted along environmental gradients, ecologists have hypothesised that these patterns result from natural selection for an optimal leaf habit, under a given environmental regime. Such evolutionary convergence can be examined by testing if the physiological niche that is occupied by a particular leaf habit (evergreen or deciduous) is similar among regions with distinct evolutionary histories. Using a process-based model of plant growth and a constructed map of evergreen and deciduous vegetation, the physiological niche of leaf habits was quantified in four global biogeographic realms. Substantial niche overlap was found between the same leaf habit in different realms, suggesting evolutionary convergence of the physiological niche. This implies a sensitivity of leaf habit to environmental change, as environmental variables determine the geographic space where the physiological niche allows a positive carbon balance, and therefore occurrence of the leaf habit. Since the physiological niche consists of the integrated effects of physiological traits and trade-offs, environmental dependencies and leaf habit and phenology, an understanding of the carbon economy of individual plants requires decomposing the physiological niche into its components. Using empirical data on leaf phenology, leaf habit and physiological processes from woody species in a seasonally dry African savanna, a simple carbon balance model was parametrised. Carbon gain varied considerably between species as a result of substantial variation in leaf habit, leaf phenology and physiological traits. The multiple lines of evidence in this thesis therefore suggest that, while convergent selective forces may determine the dominant leaf habit in a particular environment, inter-specific variation is substantial, potentially as a consequence of historical contingencies or competitive interactions.