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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.
Yuanmou Basin of Yunnan, SW China, is a famous locality with hominids, hominoids, mammals and plant fossils. Based on the published megaflora and palynoflora data from Yuanmou Basin, the climate of Late Pliocene is reconstructed using the Coexistence Approach. The results indicate a warm and humid subtropical climate with a mean annual temperature of ca. 16–17°C and a mean annual precipitation of ca. 1500–1600 mm in the Late Pliocene rather than a dry, hot climate today, which may be due to the local tectonic change and gradual intensification of India monsoon. The comparison of Late Pliocene climate in Eryuan, Yangyi, Longling, and Yuanmou Basin of Yunnan Province suggests that the mean annual temperatures generally show a latitudinal gradient and fit well with their geographic position, while the mean annual precipitations seem to be related to the different geometries of the valleys under the same monsoon system.
We have analysed the microseismic activity within the Rwenzori Mountains area in the western branch of the East African Rift. Seismogram recordings from a temporary array of up to 27 stations reveal approximately 800 events per month with local magnitudes ranging from –0.5 to 5.1. The earthquake distribution is highly heterogeneous. The majority of located events lie within faults zones to the East and West of the Rwenzoris with the highest seismic activity observed in the northeastern area, where the mountains are in contact with the rift shoulders. The hypocentral depth distribution exhibits a pronounced peak of seismic energy release at 15 km depth. The maximum extent of seismicity ranges from 20 to 32 km and correlates well with Moho depths that were derived from teleseismic receiver functions. We observe two general features: (i) beneath the rift shoulders seismicity extends from the surface down to ca. 30 km depth; (ii) beneath the rift valley seismicity is confined to depths greater than 10 km. From the observations there is no indication for a crustal root beneath the Rwenzori Mountains. The magnitude frequency distribution reveals a b-value of 1.1, which is consistent with the hypothesis that part of the seismicity is caused by magmatic processes within the crust. Fault plane solutions of 304 events were derived from P-polarities and SV/P amplitude ratios. More than 70 % of the source mechanisms exhibit pure or predominantly normal faulting. T-axis trends are highly uniform and oriented WNW-ESE, which is perpendicular to the rift axis and in good agreement with kinematic rift models. At the northernmost part of the region we observe a rotation of the T-axis trends to NEN-SWS, which may be indicative of a local perturbation of the regional stress field.
Spatial variations of nitrogen trace gas emissions from tropical mountain forests in Nyungwe, Rwanda
(2012)
Globally, tropical forest soils represent the second largest source of N2O and NO. However, there is still considerable uncertainty on the spatial variability and soil properties controlling N trace gas emission. Therefore, we carried out an incubation experiment with soils from 31 locations in the Nyungwe tropical mountain forest in southwestern Rwanda. All soils were incubated at three different moisture levels (50, 70 and 90 % water filled pore space (WFPS)) at 17 °C. Nitrous oxide emission varied between 4.5 and 400 μg N m−2 h−1, while NO emission varied from 6.6 to 265 μg N m−2 h−1. Mean N2O emission at different moisture levels was 46.5 ± 11.1 (50 %WFPS), 71.7 ± 11.5 (70 %WFPS) and 98.8 ± 16.4 (90 %WFPS) μg N m−2 h−1, while mean NO emission was 69.3 ± 9.3 (50 %WFPS), 47.1 ± 5.8 (70 %WFPS) and 36.1 ± 4.2 (90 %WFPS) μg N m−2 h−1. The latter suggests that climate (i.e. dry vs. wet season) controls N2O and NO emissions. Positive correlations with soil carbon and nitrogen indicate a biological control over N2O and NO production. But interestingly N2O and NO emissions also showed a positive correlation with free iron and a negative correlation with soil pH (only N2O). The latter suggest that chemo-denitrification might, at least for N2O, be an important production pathway. In conclusion improved understanding and process based modeling of N trace gas emission from tropical forests will benefit from spatially explicit trace gas emission estimates linked to basic soil property data and differentiating between biological and chemical pathways for N trace gas formation.
The Late Miocene (11.6–5.3 Ma) is a crucial period in the history of the Asian monsoon. Significant changes in the Asian climate regime have been documented for this period, which saw the formation of the modern Asian monsoon system. However, the spatiotemporal structure of these changes is still ambiguous, and the associated mechanisms are debated. Here, we present a simulation of the average state of the Asian monsoon climate for the Tortonian (11–7 Ma) using the regional climate model CCLM3.2. We employ relatively high spatial resolution (1° × 1°) and adapt the physical boundary conditions such as topography, land-sea distribution and vegetation in the regional model to represent the Late Miocene. As climatological forcing, the output of a Tortonian run with a fully-coupled atmosphere-ocean general circulation model is used. Our regional Tortonian run shows a stronger-than-present East Asian winter monsoon wind as a result of the enhanced mid-latitude westerly wind of our global forcing and the lowered present-day northern Tibetan Plateau in the regional model. The summer monsoon circulation is generally weakened in our regional Tortonian run compared to today. However, the changes of summer monsoon precipitation exhibit major regional differences. Precipitation decreases in northern China and northern India, but increases in southern China, the western coast and the southern tip of India. This can be attributed to the changes in both the regional topography (e.g. the lower northern Tibetan Plateau) and the global climate conditions (e.g. the higher sea surface temperature). The spread of dry summer conditions over northern China and northern Pakistan in our Tortonian run further implies that the monsoonal climate may not have been fully established in these regions in the Tortonian. Compared with the global model, the high resolution regional model highlights the spatial differences of the Asian monsoon climate in the Tortonian, and better characterizes the convective activity and its response to regional topographical changes. It therefore provides a useful and compared to global models, a complementary tool to improve our understanding of the Asian monsoon evolution in the Late Miocene.
Wenn Klimaforscher wissen wollen, was die Zukunft
bringt, schauen sie gern in die Vergangenheit. Während
der Kreidezeit herrschte auf der Erde ein Treibhausklima
mit atmosphärischen CO2-Gehalten, die weitaus
höher waren als heute. Welche Konsequenzen das für
die Meeresströmungen und die marinen Ökosysteme
hatte, können Geowissenschaftler heute nicht mehr direkt
messen. Bei der Spurensuche helfen ihnen die
Fossilien mikroskopisch kleiner Einzeller, deren wunderschöne
Kalkschalen als Klimagedächtnis dienen.
Occurrence and sources of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) in the aquatic environment
(2011)
The aim of the present study was to identify the sources of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) into the aquatic environment and to investigate its occurrence in rivers and wastewater treatment plants (WWTPs). Therefore, TMDD was analyzed in 441 wastewater samples from influents and effluents of 27 municipal WWTPs, in 6 sludge samples, in 52 wastewater samples from 3 sewage systems of municipal WWTPs, in 489 surface samples from 24 rivers, in 9 wastewater samples of 3 paper-recycling industries and in 65 groundwater samples. TMDD was also analyzed in household paper products, in 23 samples of toilet
papers, in 5 types of paper towels and in 12 types of paper tissues. The samples were collected between 2007 and 2011. The water samples were extracted with solid phase extraction (SPE) and the household paper samples with Soxhlet extraction. Gas chromatography-mass spectrometry (GC-MS) was used for quantification purposes. Between November 2007 and January 2008, TMDD was detected in the river Rhine at Worms with permanent high concentrations (up to 1330 ng/L). The results showed that TMDD is uniformly distributed across the river at Worms. An increase of the mean TMDD concentration from approximately 500 ng/L to 1000 ng/L was registered in January 2008. Due to the minor fluctuations of the TMDD concentration during the sampling period it is expected that the input of TMDD into the river is continuous. Therefore, TMDD might rather originate from effluents of municipal WWTPs than from temporal sources. The mean TMDD load based on the analysis of 147 water samples collected in the River Rhine was 62.8 kg/d which is equivalent to 23 t/a suggesting that TMDD must be used and/or produced in high quantities in order to be found in those high concentrations. To determine if TMDD is discharged by effluents of municipal WWTPs into the rivers, 24 hours influent and effluent samples of four municipal WWTPs in the Frankfurt/Rhine-Main metropolitan region were collected during November 2008 and February 2010 and analyzed for TMDD. The TMDD influent concentrations varied between 134 ng/L and 5846 ng/L and the effluent concentrations between <LOQ (limit of quantitation) and 3539 ng/L. The TMDD elimination rates in the four WWTPs varied between 33% and 68%. The results showed that effluents of municipal WWTPs are an important source of TMDD in the aquatic environment because TMDD is not completely removed from the sewage during the wastewater treatment. Weekly and daily variations of the TMDD concentration in the influents of two municipal WWTPs indicated that both private households and indirect industrial dischargers contribute to the introduction of TMDD into the municipal sewage systems. A more detailed study of the TMDD elimination rate in the different wastewater treatment stages was carried out in the WWTP Niederrad/Griesheim in Frankfurt am Main. The results showed that the removal of TMDD is mainly carried out during the aerobic biological treatments, where the elimination rate was 46%. In contrast, during the anoxic treatment the removal efficiency was only 1.4% and during the mechanical treatment the elimination rate was 19%. To determine the sources of TMDD in the sewage, household paper products (paper tissues, toilet papers and paper towels) were analyzed for TMDD using Soxhlet extraction. TMDD was detected in 83% of the samples (n=40). The highest mean TMDD concentrations were found in recycled toilet paper (0.20 μg/g) and in paper towels (0.11 μg/g). In paper tissues and non-recycled toilet paper the mean TMDD concentrations were lower 0.080 μg/g and 0.025 μg/g respectively. According to these results the high TMDD influent concentrations found previously in municipal WWTPs (mean 1.20 μg/L) cannot be explained due to migration of TMDD from the household paper products into the sewage. Thus indirect industrial dischargers are the cause of the high influent TMDD concentrations. Effluents of municipal WWTPs with different indirect industrial dischargers (textile-, metal processing-, food processing-, electroplating-, paper-recycling- and printing ink factories) were analyzed. The highest mean TMDD concentrations were found in the effluents of municipal WWTPs that have paper-recycling (71.3 μg/L) and printing ink factories (138 μg/L) as indirect industrial dischargers. These results were confirmed by analyzing process wastewater of three paper-recycling factories located in Germany. High TMDD concentrations were detected and fluctuated between 1.83 μg/L and 113 μg/L. TMDD was also analyzed in the wastewater of a non-recycling-paper factory but its concentration was much lower (0.066 μg/L) indicating that TMDD is introduced into the processing water during the papermaking process due to the use of waste paper. Analyses of wastewater samples from different parts of the sewage pipes of a municipal WWTP in Hesse, which receives the wastewater from a printing ink factory, were carried out. The TMDD concentration in the wastewater sample from the sewage pipe of the printing ink factory was much higher (3,300 μg/L) than the TMDD concentration detected in the other wastewater samples from the sewage system (0.030 μg/L – 0.89 g/L). These results confirm the printing ink production as one of the principal sources of TMDD in the sewage. Analysis of surface water samples of the River Modau downstream from the effluent of the WWTP Nieder-Ramstadt showed TMDD concentrations of up to 28.0 μg/L. These high TMDD concentrations might be caused by the indirect wastewater discharges of a paint factory connected to the municipal sewage system. These results indicate that TMDD is introduced into the municipal WWTPs principally by indirect industrial dischargers and they are mainly paint and printing ink factories. The paper-recycling factories also represent an important source of TMDD in municipal WWTPs but indirectly. According to statements given by the representatives of two paper recycling factories neither TMDD or any other TMDD containing product is used or added during the papermaking process. Therefore, TMDD is washed out from the printing inks of the coloured waste paper and concentrated in the process wastewater in the closed water circuits of paper-recycling factories reaching rivers and municipal WWTPs. The occurrence and distribution of TMDD in surface waters in Germany was also studied. The results showed that TMDD is widely distributed across different rivers systems in the federal states of Hesse, North-Rhine-Westphalia, Bavaria, Baden-Wuerttemberg and Rhineland-Palatinate. In Hesse, TMDD was detected in the some of main rivers with mean concentrations of 812 ng/L (Schwarzbach, Hessian Ried), 374 ng/L (Kinzig), 393 ng/L (Main, at Frankfurt), 539 ng/L (Werra), 326 ng/L (Fulda), 151 ng/L (Emsbach) and 161 ng/L (Nidda). In small rivers (creeks) the mean TMDD concentrations varied between <LOQ (Diemel, Urselbach) and 1890 ng/L (Darmbach). The results showed that the TMDD concentrations in creeks are highly influenced by both effluents of WWTPs and by the distance between the sampling point and the nearest WWTP. Surface samples from sampling locations downstream from WWTPs dischargers showed higher TMDD concentrations (mean 518 ng/L) than sampling locations upstream from WWTPs dischargers (mean 35.1 ng/L). The behavior of TMDD during bank filtration was investigated at two locations, at a water utility company at the Lower River Rhine (urban area) and at the Oderbruch polder (rural area). The results indicated that TMDD is removed from the surface water by bank filtration at both sampling locations. The removal process is probably carried out in the first meters of the aquifer (hyporheic zone) by biodegradation processes, since TMDD does not tend to be absorbed by sediments and it was not found in the groundwater of monitoring wells. In groundwater samples from the Hessian Ried (n=23) TMDD was found only in five samples and the highest TMDD concentration was 135 ng/L. According to these results, TMDD does not represent a concern for drinking water in Germany, since it does not reach the groundwater with high concentrations and it has a low toxicity potential. The input of TMDD into the North Sea was estimated to be 60.7 t/a by considering the mean transported loads of TMDD by the River Rhine at Wesel (58.3 t/a) and Meuse in the Netherlands (2.40 t/a). The estimated discharge of TMDD by German municipal WWTPs (8.19 t/a) and paper-recycling factories (9.24 t/a) into rivers seems to be too low considering that the mean TMDD load in the River Rhine downstream from Wesel is 58.3 t/a. However, due to the high density of population and industries at the Lower Rhine it is expected that more relevant sources of TMDD are located along the Rhine River increasing the transported load. According to the results of this PhD project TMDD is a non-ionic surfactant contained in products, which are applied on surfaces (printing inks and paints) and has the potential to reach the aquatic environment. Therefore, TMDD should fulfill the requirement of a biodegradability of 80% established by the “Law on the Environmental Impact of Detergents and Cleaning Products” in Germany. However, due to the partial elimination rates of TMDD obtained in municipal WWTPs (between 33% and 68%) and to the absence of information about the execution of the biodegradation test on TMDD, it is unknown if TMDD is in accordance with this law. Otherwise, its use as surfactant in such products is questionable.
Sedimentbilanzen haben sich als Methode zur Quantifizierung von Sedimentflüssen in Raum und Zeit in den Geowissenschaften etabliert. Sie eröffnen die Möglichkeit, differenzierte Aus¬sagen über die Erosions- und Sedimentationsdynamik von Einzugsgebieten zu treffen. Ziel der vorliegenden Arbeit ist es, die holozäne Erosions- und Sedimentationsentwicklung im mesoskaligen Mittelgebirgseinzugsgebiet des Speyerbachs im Pfälzerwald zu erfassen, und räumlich und zeitlich möglichst differenziert darzulegen. Um Langzeit-Sedimentbilanzen für den Speyerbach zu berechnen wurden verfügbare Daten zum Boden, eine eigene Kartierung der Erosion und Sedimentation sowie eine intensive (OSL und 14C-) Datierung zweier Stand¬orte durchgeführt. Die Sedimente wurden durch eine direkte Kartierung erfasst. Die Erosions¬tiefe errechnet sich aus der Subtraktion der aktuellen Mächtigkeit der Hauptlagen und der Parabraunerden vom initialen Zustand (= Berechnungsgrundlage).
Die Sedimentbilanz I basiert auf öffentlich zugänglichen bodenkundlichen Punkt- und Flächendaten und hat eine Erosion von ~27 Mio. m³ mit einem Einzugsgebiets-Sedimentaus¬tragsverhältnis (CSDR) von 31,5 % ergeben. Die Sensitivitätsanalyse belegt eine hohe Abhängigkeit des Ergebnisses von der Wahl der Berechnungsgrundlage. Aufgrund fehlender Daten sind eine höhere räumliche Auflösung sowie Aussagen zur zeitlichen Entwicklung nicht möglich.
Die Berechnung der Sedimentbilanz II erfolgte auf der Grundlage eigens erhobener Punkt- und Flächendaten, womit die Anwendung eines nested approach möglich wurde: Neben der Gesamtbilanz für den Speyerbach (sechste Strahler-Ordnung) wurden Bilanzen für Teilein¬zugsgebiete erster und vierter Strahler-Ordnung erstellt, anhand derer die Skalenabhängigkeit der Sedimentdynamik diskutiert werden konnte. Es wurden ~109 Mio. m³ und ein CSDR von 5 % errechnet und ebenfalls eine hohe Sensitivität gegenüber der Änderung der Erosionstiefen festgestellt.
Die erfolgreiche Datierung von periglazialen Deckschichten zweier Bodenprofile unterstützt die Ergebnisse der Landnutzungsrekonstruktion aus Literaturdaten und historischen Karten und zeigt, dass in den Tälchen erster Ordnung Erosion verstärkt in der Neuzeit stattfand. Nur in den lösslehmbeeinflussten Gebieten hat sich die Besiedlung im Frühmittelalter in der Ablagerung von Bodensedimenten abgebildet. Es wurden frühholozäne Umlagerungsprozesse am Hang identifiziert. Aufgrund der guten Datierungseigenschaften der sandigen periglazia¬len Lagen wäre das Untersuchungsgebiet geeignet, der Frage nach der Parallelisierung der frühholozänen Umlagerungen von Hangsedimenten mit Klimaschwankungen nachzugehen.
Die vorliegende Arbeit liefert mit den erstellten Sedimentbilanzen und der Darlegung der Landnutzungsverhältnisse ein regionales Beispiel für Mittelgebirgsräume im Rhein-Einzugs¬gebiet. Die mikro- bis mesoskaligen Ergebnisse folgen der generellen Tendenz anderer welt¬weiter Studien, wonach die Sedimentaustragsverhältnisse mit steigender Einzugsgebietsgröße abnehmen. Die Werte der Sedimentbilanz II liegen jedoch deutlich unter denen der Lössge¬biete und belegen, dass sich die Zwischenspeicherung in der Mittelgebirgsregion höher ist. Die räumliche Differenzierung zeigt regionale Unterschiede, die auf der Zugänglichkeit, der administrativen Zugehörigkeit und die naturräumliche Ausstattung zurückzuführen sind. Arbeiten in anderen Sandsteinregionen Deutschlands sind derzeit im Gange und werden in Zukunft eine Einschätzung der vorliegenden Untersuchung zulassen.