80 search hits
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The formation and the geochemical and thermal evolution of the lithospheric mantle beneath the Kaapvaal craton recorded by subcalcic garnets from harzburgites and by pristine eclogites and garnet-pyroxenites
(2012)
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Qiao Shu
- The mantle xenoliths collected by kimberlites indicate that the subcratonic mantle underneath the Archean crust is mostly a residue of high degrees of partial melting which was subsequently reenriched. The majority of the xenoliths show cryptic metasomatism and only few modal metasomatism.
Much effort has been put into deciphering different kinds of enrichment processes within the mantle. Here, we take the approach to look into the inventory of subcalcic garnets which stem from cpx-free harzburgites and dunites. These subcalcic garnets, commonly with sinusoidal REE patterns, carry the major budget of the trace elements of their host rock. Thus, they are promising objects to study both depletion and enrichment. Most importantly, the analysis of a single grain subcalcic garnetwill provide almost all important information of the bulk rock. Our aim is to gain detailed information mainly on metasomatism on a craton wide scale by combining major, trace elements and Lu-Hf and Sm-Nd isotopic signatures from subcalcic garnets. Eventually, we will summarize the metasomatic agent(s) and processes and possibly the timing of the enrichment within the lithospheric mantle underneath the Kaapvaal craton.
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Insights into rifting from seismic noise variations, shear wave splitting and b value analyses: case study beneath the Rwenzori Region, East African Rift System
(2012)
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Arthur Godfrey Batte
- This research was conducted in the Rwenzori Region of the Western Branch, East African Rift System (EARS). The EARS is a tectonic structure extending over a length of more than 3000 km from the Afar Triple Junction, in Ethiopia, to Lake Malawi in the south. The Western Rift System is a roughly NE to ENE trending sector of the EARS, which runs along the western boundary of Uganda and the neighboring Democratic Republic of Congo (D.R.C). It stretches 2100 km from Nimule, NW on Uganda-Sudan border, extending to Lake Malawi in the SE of Africa. The unusual uplift of the Rwenzori Mountains within an extensional regime and the mechanisms associated with the high frequency of seismic activity in the region was hardly understood and therefore, had remained a subject of contention that needed to be critically addressed in detail. To my knowledge, this was probably the first study to be performed and documented in great depth within the domains of seismic noise variation, seismic anisotropy and b value analyses beneath the Rwenzori Region. After about six years of operation (2006-2012), the seismology group of the RIFTLINK Research Project (www.riftlink.org) acquired a vast amount of high-quality, digital data that were collected using a seismic network of well calibrated seismic equipment. The project was divided into two phases. Phase I, that operated between February 2006 - September 2007, consisted of thirty-two temporary seismic stations, which were selectively spread out in the Rwenzori Region on the Ugandan side, to detect and record extremely weak as well as strong naturally occurring earthquakes. The seismic equipment used included EDL and REFTEK digitizers, which were coupled with Güralp and MARK sensors respectively (REFTEKS: only short-period MARK sensors, EDLs: short-period MARK plus few broadband Güralp Sensors). Exactly 22375 earthquakes were recorded. The data were processed using the SEISAN software package. About 14413 earthquakes were carefully localized using the velocity model of Bram (1975) that implements a Vp=Vs ratio fixed at 1.74. Phase II, that extended between 2009-2012 consisted of thirty-two seismic stations, which were spread out around the Rwenzori Mountains, both on the Ugandan side and the neighboring D.R.C. Only Taurus digitizers that were coupled with Trillium sensors were used in the D.R.C. On the Ugandan side however, both EDL and Taurus digitizers, which were coupled with Trillium and Güralp sensors were used...
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Entwicklung der transdisziplinären Methode "Akteursbasierte Modellierung" und ihre Anwendung im Problemfeld der mobilen, organischen Fremdstoffe : die Verknüpfung von Akteurswahrnehmungen, partizipativer Szenarienentwicklung und sequentieller Modellierung von Handlungsentscheidungen
(2010)
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Christiane Döll
- Die vorliegende Arbeit wurde im Rahmen des Forschungsprojekts „Integrierte Analyse von mobilen, organischen Fremdstoffen in Fließgewässern“ (INTAFERE) am Institut für Physische Geographie an der Goethe-Universität Frankfurt erstellt. In INTAFERE wurde das Gefährdungspotenzial von mobilen, organischen Fremdstoffen (MOF) für aquatische Ökosysteme und die natürlichen Wasserressourcen in integrierter und partizipativer Art und Weise untersucht. MOF sind chemische Substanzen, die in Alltagsprodukten enthalten sind und durch unterschiedliche Eintragsfade in unbekannten Mengen in Oberflächengewässer eingetragen werden. Problematisch sind aus Umweltgesichtspunkten ihre Eigenschaften: sie besitzen im Wasser eine hohe Mobilität und sind schwer abbaubar. Dies führt zu einer Persistenz über lange Zeiträume. Für einige dieser Substanzen wurde zudem gezeigt, dass sie in sehr geringen Konzentrationen biologisch aktiv sind und für aquatische Ökosysteme eine Gefahr darstellen. In INTAFERE wurden drei zentrale Ziele verfolgt: Charakterisierung des Problemfeldes MOF, Erzeugung von praxisrelevantem Wissen für das Management von MOF und Entwicklung einer Softwareanwendung, die gesellschaftliche Aushandlungsprozesse durch eine transparente Darstellung der Wirkungszusammenhänge im Problemfeld unterstützt. Um einen Beitrag für die Erfüllung der Ziele zu leisten, war es die Aufgabe der Verfasserin, eine Akteursanalyse und -modellierung durchzuführen sowie Zukunftsszenarien im Bereich der MOF zu entwickeln. Dafür existierte keine adäquate Methodik, daher verfolgt die Dissertation zum einen die Entwicklung einer Methodik und zum anderen deren Anwendung im Kontext des Projektes INTAFERE. Da im Forschungsprozess die Durchführung von Analysen, die wissenschaftliche und gesellschaftliche Sichtweise der Problematik sowie die Erarbeitung von praktischen Lösungen im Mittelpunkt standen, wurde eine transdisziplinäre Herangehensweise gewählt. Ziel war es, eine Methodik zu entwerfen, die sowohl eine Entwicklung von Szenarien als auch eine Modellierung von Handlungsentscheidungen umfasst. Eine Modellierung und Visualisierung von Handlungsentscheidungen ist notwendig, um Strategien für ein Umweltproblem für verschiedene Szenarien zu ermitteln, und damit einen Lernprozess der Stakeholder zu initiieren. Dies wurde mit der transdisziplinären Methode „Akteursbasierte Modellierung“ umgesetzt. Hierbei wurden insbesondere Aspekte der Problemwahrnehmung von Akteuren und deren Darstellung, der partizipativen Szenarienentwicklung sowie der semi-quantitativen Modellierung von Handlungsentscheidungen berücksichtigt. Die Verfasserin hat mit der semi-quantitativen akteursbasierten Modellierung eine Methode erarbeitet und getestet, die bisher unverbundene Komponenten (wie die Software Dynamic Actor Network Analysis (DANA) und die Szenarienentwicklung) zusammenführt. Um Handlungsentscheidungen unter verschiedenen Szenarien zu modellieren hat die Autorin eine sequentielle Modellierung entwickelt, die mit der Software DANA durchgeführt werden kann. Die dafür notwendige Weiterentwicklung von DANA wurde von Dr. Pieter Bots (TU Delft) umgesetzt. Die akteursbasierte Modellierung läuft in drei methodischen Schritten ab: 1. Modellierung von Akteurs-Sichtweisen in Form von Wahrnehmungsgraphen und deren Analyse, aufbauend auf Ergebnissen von qualitativen, leitfaden-gestützten Expertengesprächen (= Akteursmodellierung), 2. partizipative Szenarienentwicklung mit den Akteuren und 3. Zusammenführung der Ergebnisse der Akteursmodellierung und der Szenarienentwicklung und darauf aufbauend eine sequentielle Modellierung von Handlungsentscheidungen und deren Auswirkungen auf Schlüsselfaktoren. Im Zuge der Anwendung auf das Problemfeld der MOF wurde für folgende Akteure jeweils ein Wahrnehmungsgraph modelliert: Obere Wasserbehörde, Umweltbundesamt, Umwelt- und Verbraucherschutzorganisationen, Wasserversorger sowie für die Hersteller von verschiedenen MOF, weiterhin für die European Flame Retardants Association und die Weiterverarbeitende Industrie. Das Ergebnis der Szenarienentwicklung waren vier Szenarien: ein Gesundheitsszenario, unter der Annahme von hohen lokalen Umweltstandards durch nachhaltigkeitsorientierte KonsumentInnen, ein Umweltszenario, in dem eine starke Regulierung und nachhaltigkeitsorientierter Konsum Hand in Hand gehen, ein Globalisierungsszenario, in dem Wirtschaftsmacht und preisbewusste KonsumentInnen statt staatliche Regulierung vorherrschen und ein Technikszenario, unter der Annahme, dass Kläranlagen, bedingt durch eine starke Regulierung, aufgerüstet werden. Bei der Modellierung von Handlungsentscheidungen wurden die Wahrnehmungsgraphen und die vier Szenarien miteinander verknüpft. Pro Substanz wurde ein Modell entwickelt, welches die wichtigsten Systemkomponenten in einer angemessenen Komplexität umfasst und die von den Akteuren gemeinsam getragene Einschätzung der Wirkungsbeziehungen darstellt. Insgesamt wurden 16 Modelle entwickelt. Basierend auf den simulierten Akteurshandlungen wurden relativen Veränderungen der Schlüsselfaktoren Produktion, Import und Leistungsfähigkeit der Kläranlagen für die vier genannten Szenarien berechnet. In Zusammenarbeit mit Pieter Bots konnten algorithmische Beiträge zur Analyse- und Modellierungssoftware DANA getestet und verbessert werden. Da keine vollständige und zugleich leicht verständliche Einführung zu DANA vorlag, wurde für Nutzer im Rahmen dieser Dissertation eine Anleitung verfasst, die die Modellierung von Wahrnehmungsgraphen und deren Analyse sowie alle Schritte der akteursbasierten Modellierung mit DANA erläutert.
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Coupling of geological processes in the Earth’s crust and mantle
(2012)
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Timo Luchs
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On the interaction between thermal tides and gravity waves in the middle atmosphere
(2012)
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Fabian Senf
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Occurrence and sources of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) in the aquatic environment
(2011)
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Arlen Guedez Orozco
- 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.
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The radiation budget in a regional climate model
(2011)
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Steffen Kothe
- The aim of this study is a better understanding of radiation processes in regional climate models (RCMs) in order to quantify their impact and to reduce possible errors. A first important task in finding an answer to this question was to examine the accuracy of the components of the radiation budget in regional climate simulations. To this end, the simulated radiation budgets of two regional climate simulations for Europe were compared with a satellite-based reference. In the simulations with the RCM COSMO-CLM there were some serious under- and overestimations of short- and long-wave net radiation in Europe. However, taking into account the differences in the reference datasets, the results of the COSMO-CLM were quite satisfactory.
Using statistical methods, the influence of potential sources of uncertainties was estimated. Uncertainties in the cloud cover and surface albedo had a significant impact on uncertainties in short-wave net radiation, the explained variance of uncertainties in cloud cover was two to three times higher than that of uncertainties in surface albedo. Uncertainties in the cloud cover resulted in significant errors in the net long-wave radiation. However, the influence of uncertainties in soil temperature on errors in the long-wave radiation budget was low or even negligible. These results were confirmed in a comparison with simulations of the REMO and ALADIN regional climate models. It is reasonable to expect that a better parameterization of relatively simple parameters such as cloud cover and surface albedo is a means of significantly improving the simulation of radiation budget components in the COSMO-CLM.
An important question for the application of RCMs is to examine whether the results of radiation uncertainties and their impact factors are comparable if the model is applied in a region that is not the one for which it was originally created. Comparisons of the simulated radiation budgets of different RCMs for West Africa showed that problems in the simulation of short- and long-wave radiation fluxes were a widespread problem. Most of the tested models showed some considerable under- or overestimation of the short- and long-wave radiation fluxes.
Similar to Europe uncertainties in cloud cover were also in the simulations for Africa a significant factor affecting uncertainties in the simulated radiation fluxes. However, for the African simulations uncertainties in the parameterization of surface albedo were much more important than in Europe. On average, overland uncertainties in the cloud cover and surface albedo were of similar importance. Uncertainties in soil temperature simulations were of higher importance in Africa, and reached overland similar values of the mean explained variance
(R2 ≈ 0.2) such as uncertainties in the cloud cover. This indicates a geographical dependence of the model error. This study confirmed the assumption that an improved parameterization of relatively simple parameters such as the surface albedo in RCMs leads to a significant improvement in the modeled radiation budget, particularly in Africa.
The influence of errors in the simulated radiation budget components on the simulation of climate processes, such as the West-African monsoon (WAM), was investigated in a next step. The evaluation of ERA-Interim and ECHAM5 driven COSMO-CLM simulations for Africa showed that the main features of the WAM were well reproduced by the model, but there were only slight improvements compared to the driving data. The index of convective activity in the model simulations was much too high and precipitation was underestimated in large parts of tropical Africa. The partly considerable differences between the ERA-Interim and ECHAM5 driven simulations demonstrated the sensitivity of the RCM to the boundary conditions and in
particular to the sea surface temperature. An excessive northwards shift of the monsoon in the model was influenced by the land-sea temperature gradient and the strength of the Saharan heat low. Consequently, a part of the error was due to the driving data and the model itself produced another part.
By modifying the parameterization of the bare soil albedo the errors in the radiation budget
and 2 m temperature in the Sahara region were significantly reduced. Similarly, the overesti-mation of precipitation and convection has been reduced in the Sahel. The effect of this modifi-cation on the examined WAM area was low. This confirmed that especially in desert regions, errors in the surface albedo were a driving factor for errors in the radiation budget. However, there are other important factors not yet sufficiently understood that have a strong influence on the quality of the simulation of the WAM.
The analysis of the actual state, the quantification of error sources and the highlighting of connections made it possible to find means to reduce uncertainties in the simulated radiation in RCMs and to have a better understanding of radiation processes. However, the magnitude of the errors found, the number of possible influencing factors, and the complexity of interactions, indicate that there is still a need for further research in this area.
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The Holsteinian interglacial (MIS 11c) as a palaeoclimatic analogue to the Holocene : comparison of climate and ecosystem variability
(2011)
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Andreas Koutsodendris
- Owing to long-term similarities with regard to orbital climate forcing (i.e., low eccentricity and
a dampened influence of precession), Marine Isotope Stage (MIS) 11 represents one of the
closest astronomical analogues for present and future climate. Hence, insights into the
climate variability of MIS 11 can contribute to a better understanding of the climatic evolution
of the present (Holocene) interglacial as it would occur without human interference. In order
to elucidate the natural climate variability during MIS 11, this study examines predominantly
annually laminated lake sediments of Holsteinian age from Dethlingen, northern Germany.
The Holsteinian interglacial is widely accepted to be the terrestrial equivalent of MIS 11c in
central Europe and can be biostratigraphically correlated with the Hoxnian, Mazovian and
Praclaux interglacials on the British Isles, in Poland and in France, respectively. These
correlations yield the potential to cross-check the results from individual sites on a regional
scale. This study is based on a multi-proxy approach including palynological,
micropaleontological, sedimentological, geochemical and time series analyses within a wellconstrained
chronological framework that has been established through varve counting and
regional bio-stratigraphic correlations with other annually laminated archives of Holsteinian
age. In particular, the here-presented study aims at (i) fingerprinting the long-term
(centennial- to millennial-scale) and short-term (sub-decadal- to decadal-scale) climate
variability during the Holsteinian interglacial, (ii) deciphering the nature, tempo and trigger
mechanisms of abrupt climate change under interglacial boundary conditions, and (iii)
assessing its impact on terrestrial ecosystems.
With regard to long-term climate variability, the vegetation succession at Dethlingen as
inferred from pollen data provides insights into the mesocratic to telocratic forest phases of a
glacial-interglacial cycle spanning ~11500 (± 1000) years of the 15-16-ka-long Holsteinian
interglacial. The development of temperate mixed forests suggests a general prevalence of
mild climatic conditions during the Holsteinian. The older parts of the interglacial are
characterised by the strong presence of boreal tree taxa (e.g., Picea), whereas the younger
parts of the interglacial are marked by the expansion of sub-Atlantic to Atlantic forest
elements (e.g., Abies, Buxus, Ilex, Quercus) and the decline of boreal tree taxa. This
vegetation succession suggests a general warming trend and decreasing seasonality over
the course of the Holsteinian interglacial. Based on the maximum pollen abundances of
indicator tree taxa (e.g., Buxus and Quercus), peak warmth was reached during the later
stages of the interglacial; it was accompanied by high humidity. The forest succession of the
Holsteinian interglacial was punctuated by abrupt and gradual changes in the abundances of
temperate plant taxa. These vegetation changes indicate considerable intra-interglacial
climate variability. In particular, two marked declines of temperate taxa leading to the
transient development of boreal and sub-boreal forests were triggered by centennial-scale
climate oscillations, here termed Older and Younger Holsteinian Oscillations (OHO and
YHO). These oscillations occurred ~6000 and ~9000 years after the onset of the interglacial
pioneer forestation in central Europe, respectively.
To assess the impact of abrupt climate change on terrestrial ecosystems during the
Holsteinian and to investigate the underlying driving mechanisms, the intervals spanning the
OHO and the YHO at Dethlingen were subjected to decadal-scale palynological and
sedimentological analyses. Based on these data, the OHO comprises a 90-year-long decline
of temperate taxa associated with expansion of Pinus and non-arboreal pollen, and a
subsequent 130-year-long recovery of temperate taxa marked by the pioneer expansion of
Betula and Alnus. Owing to its highly characteristic imprint on vegetation dynamics, the OHO
can be identified in pollen records from the central European lowlands north of 50º latitude,
from the British Isles to Poland. A close inspection of individual pollen records from that
region reveals the prevalence of colder winters during the OHO, with a gradient of
decreasing temperature and moisture availability, and increased continentality towards
eastern Europe. This climate pattern points to a weakened influence of the westerlies and/or
stronger influence of the Siberian High connected to the OHO.
The vegetation dynamics during the YHO are characterised by a decline of temperate taxa
(particularly of Carpinus) and the expansion of pioneer trees (mainly Betula). In contrast to
the OHO, frost-sensitive taxa (e.g., Ilex, Buxus and Hedera) continued to thrive. This
suggests that mean winter temperatures remained relatively high (>0 ºC) during the YHO
pointing to a decrease of summer warmth related to the climatic deterioration. The YHO,
which has a duration on the order of 300 years, is centered within a long-term (~1500-year)
decline and subsequent, millennial-scale recovery of temperate taxa.
Because the impact of the OHO and the YHO on the vegetation at Dethlingen was markedly
different, both short-term climate oscillations may have been caused by different trigger
mechanisms. For the OHO, the inferred regional-scale winter cooling over central Europe
lasting for several decades points to a decrease in ocean heat transport, most likely related
to a transient slowdown in North Atlantic Deep Water formation. This view is supported by
the strong resemblance of the OHO to the 8.2 ka event of the Holocene with regard to the
duration, imprint on terrestrial ecosystems, spatial pattern of the climatic impact, timing within
the respective interglacial, and prevailing interglacial boundary conditions. In contrast, the
presence of frost-sensitive taxa during the YHO appears to exclude a reduction in oceanic
heat transport as postulated for the OHO. Instead, the long-lasting, gradual changes in the
abundances of temperate taxa suggest a connection to orbital forcing, with the triggering
mechanism causing the centennial-scale vegetation setback itself remaining unclear.
The characteristics of short-term climate variability were investigated based on microfacies
and time series analyses of a ~3200-year-long, annually laminated window of the Dethlingen
record. The annual laminations at Dethlingen comprise biogenic varves consisting of two
discrete sub-layers. The light layers, which are controlled by the intensity of diatoms blooms
during spring/summer, reflect changes in the productivity of the Dethlingen palaeolake. In
contrast, the dark layers, which consist predominantly of amorphous organic matter and
fragmented diatom frustules, represent sediment deposition during autumn/winter. Spectral
analyses of the thicknesses of the light and dark layers have revealed several peaks
exceeding the 95% and 99% confidence levels that are near-identical to those known from modern instrumental data and Holocene records. Decadal-scale signals at periods of 90, 25,
and 10.5 years are likely associated with the 88-, 22- and 11-year solar cycles; hence, solar
activity appears to have been a forcing agent in productivity changes of the Dethlingen
palaeolake. Sub-decadal-scale signals at periods between 3 and 5 years and ~6 years may
reflect an influence of the El Niño-Southern Oscillation (ENSO) and the North Atlantic
Oscillation (NAO) on varve formation during winter.
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The Cenozoic salt diapir near Eyvanekey and Garmsar, Iran: new insights from structural investigations and analogue modeling
(2010)
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Shahram Baikpour
- The Alborz Mountains are forming a ~100 km wide, E-W trending mountain chain where individual summits are up to 5000 m in elevation. The Alborz Mountains range are part of the Alpine orogen and are straddling a 2000 km wide area S of the Caspian Sea. The rocks of the Alborz Mountains consist of Neogen sediments, which are affected by folding and faulting. In the western part of the Alborz Mountains the folds and faults are trending NW-SE, whereas in the eastern part they are trending NE-SW. GPS data confirm N-S shortening including dextral strike-slip along ESE-WNW trending faults, and sinistral strike-slip along ENE-WSW trending faults. The present thesis is focusing on the active Garmsar salt nappe, the fragmented roof of which is pierced by rock salt which extruded near the front of the Alborz Mountains Range. During the past 5 m.y. the front of the Alborz chain migrated towards SSW on top of the salt of the Garmsar basin. The salt was squeezed towards SSW and took place at the Great Kavir. The extruded salt is forming the Eyvanekey plateau between the cities of Eyvanekey and Garmsar. Both the Garmsar salt nappe and the Eyvanekey plateau are dextrally displaced for ca. 9 km along the Zirab-Garmsar fault. Structural analyses of the Garmsar salt nappe indicate three different groups of joints which are trending perpendicular and parallel to the local mechanical anisotropy. The folds of the study area are congruent (type 2 and 3 after Ramsay) resulting from viscose inhomogeneous flow. InSAR-Investigations suggest the Alborz Mountains to be lifted up by ca. 1 cm/a, while horizontal shortening is active at a rate of 8 ±2 mm/a. These values are consistent with GPS data. Based on nine „Advanced Synthetic Aperture Radar“ (ASAR) scenarios, produced by the ENVISAT satellite of the European space agency between 2003 and 2006, we used interferograms to map the displacement via 22 increments during 2 – 18 months. The results suggest that the topographic height of the surface of the salt is changing at a rate which is controlled by the season. The displacement ranges from subsidence at -40 to -50 mm/a to uplift of 20 mm/a. In order to investigate the time-dependent deformation with high spatial resolution, we used algorithms which are based on data of small base lines (SBAS). The resulting interferometric SAR time series analyses also suggest that the study area is largely subsiding at a rate that is controlled by the seasons. The map with the averaged LOS deformation velocities, on the other hand, suggests the subsidence to increase from the upper part of the salt nappe towards deeper topographic 5 levels of the agricultural lowlands. The major part of subsidence is probably caused by the annual rainfall which results in subrosion of salt. The spatial changes in the subsidence rate are probably controlled by the distribution of fountains, mining activity at the margin of the salt glacier, and faults and fractures inside the salt. Striking seasonal imprints are obvious along the agricultural areas which are surrounding the Garmsar salt nappe. These areas are rapidly subsiding in summer and spring when groundwater is used for irrigations. The maximum rate of subsidence (40-50 mm/a) is located E and W of the Eyvanekey plateau, where large areas are irrigated. The maximum displacement is 20 mm/a in the farmland and 5 mm/a in the center of the salt nappe. Depth estimates using Euler deconvolution method for gravimetric and magnetic data suggest the salt to extrude from a depth less than ca. 2000 m. The gravity field of the study area is characterized by strong anomalies in the SW and weak anomalies in the NE. A considerable negative anomaly in the N indicates that the northern part subsided, whereas the southern part was lifted up. The seismic data show three major horizons inside the Miocene sediments: the Lower Red Formation, the Qom Formation, and the Upper Red Formation. The western part of the study area seems to be free from salt domes. The layers of the upper part of the Qom Formation show thinning along the NE and NW trending faults. In some areas the seismic reflectors indicate steep faults close the saddle of the folds. NE-SW-, NW-SE and E-Wtrending faults prevail. Analogue experiments have been carried out to extend our knowledge about the evolution of the Garmsar salt dome. We used a scaled model (34 cm * 25 cm * 2.5 cm) that was shortened perpendicular to its long side. The wedge shape of the Alborz Mountains was simulated by a wedge consisting of Styrofoam. Rock salt was simulated using Polydimethylsiloxan (PDMS), a linear viscous material with a viscosity of 2.3*104 Pa s and a density of 0.96 g/cm3 at room temperature. Other sediments were modeled using dry quartz sand. The experimental results can be used to simulate the structural evolution of the study area: The Alborz deformation front was emplaced on top of the salt rocks in the Garmsar area while migrating towards SSW. A salt basin and a salt extrusion have also been produced in the model. Cross sections through the wedge shaped analogue model indicate N- and S-dipping reverse faults, which are in line with the wedge shape of the Alborz chain. Moreover, ENE-WSW trending sinistral and ESE-WNW trending dextral strike-slip faults led to N-S shortening during the Miocene. Structural marker horizons, 6 which have been turned into Z-folds on the western fold limbs and to S-folds on the eastern fold limbs, are comparable with the folds of the study area. Solving the problem of waste is one of the central tasks of environmental protection. It is becoming increasingly difficult to find suitable sites that are acceptable to the public. Salt and salt formations have relevant properties to be utilizing as a repository for each kind of waste. The favorable properties make rock salt highly suitable as a host rock, in particular for nonradioactive and radioactive wastes. The Qom and Garmsar basins are the nearest salt diapirs to the Tehran province, and there are suitable repositories for waste disposal. Based on surface and subsurface data, the Garmsar salt diapir has been investigated as a case example for its suitability as a host and repository for various types of waste. The data used are based on field studies, interferometry, and geophysical investigations. The results of this study suggest the deep bedded salt of the Garmsar Salt Basin to be an appropriate host for the deposition of industrial waste. Rock salt of surficial layers or domes, on the other hand, is not regarded as an appropriate candidate for waste disposal.
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Variabilität der Eiskeimkonzentration über Zentraleuropa
(2010)
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Holger Klein
- Die kumulative Dissertation beschäftigt sich mit der atmosphärischen Konzentration von Eiskeimen, einer Unterklasse des atmosphärischen Aerosols, die bei der Eisbildung in Wolken eine zentrale Bedeutung besitzt. Messungen der Eiskeimkonzentration am Taunusobservatorium (Kleiner Feldberg) (nahe Frankfurt am Main) wurden mit dem Verfahren einer Vakuum-Diffusionskammer durchgeführt. Die Arbeit umfasst die Darstellung des angewandten Messverfahrens und die Analyse und Bewertung der Messergebnisse für den Raum Zentraleuropa, anhand von u.a. Rückwärtstrajektorien und Korrelationen zu aerosolphysikalischen Parametern. Ein signifikanter Einfluss von Mineralstaub-Ferntransport aus Wüstengebieten auf die Eiskeimkonzentration in Zentral-Europa wurde ermittelt.
