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Long-term human-environmental interactions in naturally fragile drylands are a focus of geomorphological and geoarchaeological research. Furthermore, many dryland societies were also affected by seismic activity. The semi-arid Shiraki Plain in the tectonically active southeastern Caucasus is currently covered by steppe and largely devoid of settlements. However, numerous Late Bronze to Early Iron Age city-type settlements suggest early state formation between ca. 3.2-2.5 ka that abruptly ended after that time. A paleolake was postulated for the lowest plain, and nearby pollen records suggest forest clearcutting of the upper altitudes under a more humid climate during the Late Bronze/Early Iron Ages. Furthermore, also an impact of earthquakes on regional Early Iron Age settlements was suggested. However, regional paleoenvironmental changes and paleoseismicity were not systematically studied so far. We combined geomorphological, sedimentological, chronological and paleoecological data with hydrological modelling to reconstruct regional Holocene paleoenvironmental changes, to identify natural and human causes and to study possible seismic events during the Late Bronze/Early Iron Ages. Our results show a balanced to negative Early to Mid-Holocene water balance probably caused by forested upper slopes. Hence, no lake but a pellic Vertisol developed in the lowest plain. Following, Late Bronze/Early Iron Age forest clear-cutting caused lake formation and the deposition of lacustrine sediments derived from soil erosion. Subsequently, regional aridification caused slow lake desiccation. Remains of freshwater fishes indicate that the lake potentially offered valuable ecosystem services for regional prehistoric societies even during the desiccation period. Finally, colluvial coverage of the lake sediments during the last centuries could have been linked with hydrological extremes during the Little Ice Age. Our study demonstrates that the Holocene hydrological balance of the Shiraki Plain was and is situated near a major hydrological threshold, making the landscape very sensitive to small-scale human or natural influences with severe consequences for local societies. Furthermore, seismites in the studied sediments do not indicate an influence of earthquakes on the main and late phases of Late Bronze/Early Iron Age settlement. Altogether, our study underlines the high value of multi-disciplinary approaches to investigate human-environmental interactions and paleoseismicity in drylands on millennial to centennial time scales.

Während der Klimawandel und die globale Erwärmung das östliche Afrika schon heutzutage beeinflussen, ist das Wissen über die klimatischen Veränderungen der Vergangenheit begrenzt. Vor allem in den letzten 15.000 Jahren hat das östliche Afrika räumlich komplexe klimatische Veränderungen erlebt. Obwohl in Ostafrika mehrere paläoklimatische Studien durchgeführt wurden, welche die Temperaturänderungen und die hydrologische Vergangenheit von Seearchiven rekonstruierten, sind die treibenden Mechanismen und Telekonnektionen noch nicht vollständig verstanden. Ein tieferes Verständnis wird verhindert durch (i) das Fehlen von zeitlich weit zurückreichenden, qualitativ hochwertigen wissenschaftlichen Daten bezüglich Umweltveränderungen, insbesondere in der Region des Horns von Afrika, (ii) das Fehlen solcher Daten aus großen Höhen und (iii) unzureichend untersuchte Regionen wie der östliche Teil Äthiopiens und Somalia. Eines der am wenigsten untersuchten Hochgebirgsgebiete der Region sind die Bale Mountains, obwohl sie das größte Gebiet des Kontinents oberhalb von 4000 m ü. NN umfassen. Diese Dissertation zielt darauf ab, den derzeitigen Mangel an paläoklimatischen Rekonstruktionen in Hochgebirgen in der untersuchten Region am Horn von Afrika weiter zu verringern. Hochgelegene perennierende Seen, insbesondere Karseen, sind wertvolle Archive für paläoklimatische und ökologische Rekonstruktionen, da sie kontinuierliche Sedimente liefern, die durch menschliche Aktivitäten nicht gestört wurden. Der einzige ganzjährige See in den Bale Mountains, der Garba Guracha, liegt in der afro-alpinen Zone auf 3950 m ü. NN. Frühere paläolimnologische Untersuchungen ergaben, dass die kontinuierlichen Sedimente des Garba Guracha paläoklimatische und ökologische Informationen seit der letzten Vergletscherung beinhalten. Um das paläoklimatische Wissen über die Bale Mountains und damit über das östliche Afrika zu erweitern, wurden neue innovative Proxies, z. B. brGDGTs, δ18Ofucose, δ18Odiatom und δ2Hn-alkane, auf neu geborgene Sedimentkerne des Garba Guracha angewendet. Die Interpretation der Ergebnisse dieser Analysen ermöglichen ein tieferes Verständnis des Sedimentkerns, vor allem in Bezug auf die Sedimentologie, die Chronologie und die Quellen abgelagerten organischen Materials. Die hochauflösende Chronologie des Garba Guracha, die unter Verwendung verschiedener Datierungsmethoden und -komponenten (210Pb-Datierung, Radiokohlenstoffdatierung an der Gesamtsedimentfraktion, an Holzkohle und komponentenklassenspezifisch an n-Alkanen) erstellt wurde, ergibt ein basales Alter von ∼ 16 cal ka BP. Die geochemische Korrelation der Tephra-Schichten in den Garba-Guracha-Sedimenten mit datierten Tephra-Schichten aus anderen Seen der Region liefert eine externe Alterskontrolle, die die Robustheit der neuen Garba-Guracha-Chronologie und die Abwesenheit von systematischen Altersverschiebungen weiter untermauert. Ähnliche Altersangaben für n-Alkane und der Gesamtsedimentfraktion deuten darauf hin, dass die Biomarker in dem sehr kleinen afro-alpinen Einzugsgebiet kein Pre-aging vorweisen, was auf eine kurze Verweildauer oder/und eine hohe aquatische Produktivität schließen lässt. Die vorherrschende autochthone Produktion von organischem Material in dem im Vergleich zur Größe des Einzugsgebiets relativ großen See wurde durch relativ niedrige TOC/N Verhältnisse, relativ positive δ13C Werte und niedrige Werte der Zucker-Biomarker-Verhältnisse nachgewiesen. Der aquatische Ursprung von Fucose wird außerdem durch einen methodischen Vergleich von δ18Ofucose mit dem rein aquatischen δ18Odiatom Rekord unterstützt. Die gute Korrelation und ähnliche Amplitude von δ18Odiatom und δ18Ofucose (7,9 ‰ bzw. 7,1 ‰) unterstreichen nicht nur das Potenzial von δ18O-Zucker-Analysen in paläoklimatischen Studien, sondern lassen auch den Schluss zu, dass δ18Ofucose im Garba Guracha δ18OSeewasser widerspiegelt. Ohne den Einfluss des 'Amount effects' und des 'Source effects' völlig auszuschließen, interpretieren wir den δ18O-Datensatz des Garba Guracha daher als das Verhältnis von Niederschlag zu Verdunstung. Die hydrologische Vergangenheit des Garba Guracha wird von regionalen und nordhemisphärischen klimatischen Veränderungen beeinflusst. Zu Beginn des Holozäns nahmen die Niederschläge zu, was zu einem überlaufenden See zwischen ∼ 10 und ∼ 7 cal ka BP führte (erkennbar an den negativsten δ18O-Werten im gesamten Kern). Diese Phase entspricht der African Humid Period, einer räumlich unterschiedlich ausgeprägten feuchten Phase im äquatorialen und nördlichen Afrika, die durch eine verstärkte Aktivität des Westafrikanischen Monsuns und, im Fall der östlich gelegenen Bale Mountains, des Ostafrikanischen Monsuns bedingt wurde. Während die hydrologischen Veränderungen der AHP in Ostafrika durch meridionale Klimaprozesse angetrieben zu werden scheinen, zeigt das hochgelegene Garba Guracha Archiv zusätzliche Ähnlichkeiten mit rekonstruierten Monsunveränderungen in Oman. Eine kontinuierliche Verschiebung hin zu positiveren δ18O-Werten beginnt um 7 cal ka BP und deutet auf einen allmählichen Übergang von feuchtem zu trockenem Klima hin. Die Temperaturen am Garba Guracha wurden mit Hilfe einer modifizierten MBT'5ME Kalibrierung durch Hinzunahme von 6-Methyl-brGDGT IIIa' rekonstruiert (MBT'5ME Bale-Mountain-Index - r2 = 0,93, p < 0,05). Eine Anpassung der Kalibration war nötig, da die 6-Methyl-brGDGTs in den modernen Seesedimenten der Bale Mountains in bislang unbekannten Mengen auftreten und die Temperatur-Kalibrierung beeinflussen. Die rekonstruierten Temperaturänderungen sind stark von überregionalen klimatischen Einflüssen, wie Insolationsveränderungen und der AHP beeinflusst. Zusätzliche lokale Einflüsse, wie noch nicht abgeschmolzene Eismassen im Einzugsgebiet oder die Veränderungen der Hydrologie sind nicht auszuschließen. Im hochgelegenen Garba Guracha herrschten kalte Temperaturen, bis es kurz nach Beginn des Holozäns zu einer deutlichen Erwärmung (3,0 °C in weniger als 600 Jahren) kam. Zwischen 9 und 6 cal ka BP herrschte ein thermisches Maximum, das mit feuchten Bedingungen zusammenfiel und gefolgt war von einem Temperaturrückgang der bis 1.4 cal ka BP andauerte. Die Ergebnisse dieser Dissertation zeigen regionale und globale Antriebsmechanismen für klimatische Veränderungen in den Bale Mountains auf und erweitern damit das paläoklimatische Wissen über das Horn von Afrika. Der innovative methodische Ansatz dieser Arbeit hebt das Potenzial von δ18O-Zuckeranalysen und n-Alkan-Datierungen hervor. Darüber hinaus unterstreichen die Ergebnisse die Notwendigkeit einer verstärkten Grundlagenforschung, wie z. B. lokaler brGDGT-Kalibrierungsstudien, um die bestehenden wissenschaftlichen Konzepte voranzutreiben und zu präzisieren.:1.1 Table of Content List of Abbreviations v List of Tables vi List of Figures vii List of papers ix Abstract x Zusammenfassung xii Acknowledgements xiv 1 Introduction 1 1.1 Motivation 2 1.2 Objectives of the thesis 5 1.3 Background – The Bale Mountains and biomarker 6 1.3.1 Study area and archive 6 1.3.2 A short introduction to selected biomarkers applied in environmental geochemistry 8 1.4 Methods used in the thesis 10 1.4.1 Monosaccharide sugar biomarkers 11 1.4.2 Total lipid extraction for n-alkane and brGDGTs analyses 11 1.4.3 Branched Glycerol Dialkyl Glycerol Tetraether analyses 12 1.4.4 Biogeochemical analyses 13 1.4.5 Radiocarbon dating 13 1.4.6 Age depth model 13 1.5 Structure of the thesis 15 1.6 References 16 2 Revisiting afro-alpine Lake Garba Guracha in the Bale Mountains of Ethiopia: rationale, chronology, geochemistry, and paleoenvironmental implications 27 Abstract 28 2.1 Introduction 29 2.1.1 Study site 29 2.2 Material and Methods 31 2.2.1 Chronology and dating 31 2.2.2 XRF scanning 34 2.2.3 Biogeochemical analyses 34 2.2.4 n-Alkane and sugar quantification 35 2.3 Results 35 2.3.1 The sedimentary sequence – Master core and lithofacies 35 2.3.2 Chronology 37 2.3.3 Geochemistry 39 2.4 Discussion 41 2.4.1 Chronology 41 2.4.2 Origin of organic matter 43 2.4.3 Environmental implications 45 2.4.4 Comparison with lake level and other records 49 2.5 Conclusions 50 2.6 Acknowledgements 50 2.7 References 51 3 The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms 61 Abstract 62 3.1 Introduction 62 3.1.1 Regional setting 64 3.2 Material and methods 66 3.2.1 Material and sampling 66 3.2.2 Compound-specific δ18O analyses of sugar biomarkers 66 3.2.3 δ18O analyses of diatoms 67 3.3 Results 68 3.3.1 δ18Ofuc record of Garba Guracha 68 3.3.2 δ18Odiatom record of Garba Guracha 69 3.4 Discussion 69 3.4.1 The Garba Guracha δ18Osugar record - lake or leaf water? 69 3.4.2 The Garba Guracha δ18Odiatom record 70 3.4.3 Comparison of reconstructed δ18Olake water from δ18Ofuc versus δ18Odiatom 71 3.4.4 Paleoclimatic significance and proxy interpretation 72 3.4.5 Comparison with other records 75 3.5 Conclusions 77 3.6 Acknowledgements 78 3.7 References 78 4 A Holocene temperature (brGDGT) record from Garba Guracha, a high-altitude lake in Ethiopia 89 Abstract 90 4.1 Introduction 90 4.1.1 Regional setting 93 4.2 Material and Methods 94 4.2.1 Material and Sampling 94 4.2.2 Sample preparation and analysis 95 4.2.3 BrGDGTs – structure, statistical methods and proxy calculation 96 4.2.4 Quantitative data analyses 97 4.3 Result 97 4.3.1 BrGDGT patterns of surface sediments from lakes in the Bale Mountains 97 4.3.2 BrGDGT patterns of the Garba Guracha sediment core 100 4.4 Discussion 103 4.4.1 Possible MAT calibration functions inferred from the expanded eastern African surface sediment dataset 103 4.4.2 Paleotemperature reconstructions for the Garba Guracha sedimentary record - comparison of the different calibrations 104 4.4.3 Paleotemperature reconstructions for the Garba Guracha sedimentary record – regional comparison 106 4.5 Conclusions 111 4.6 Acknowledgements 111 4.7 References 112 5 Synthesis 121 5.1 Sedimentation and chronology - What is the time frame and age depth function of the Garba Guracha core? 122 5.2 Source identification What is the origin of the organic material in the Garba Guracha sediment core? 125 5.3 Hydrology δ18O as a proxy for Garba Guracha evaporation history 126 5.4 Hydrology δ2H – as a proxy for the Garba Guracha precipitation history 128 5.5 Temperature - brGDGTs - as a proxy for Garba Guracha MAT history 129 5.6 Garba Guracha environmental and climate reconstruction – Why and how has the climate changed? 131 5.6.1 Deglaciation 132 5.6.2 North hemisphere forcings in the Garba Guracha catchment during the Younger Dryas period 132 5.6.3 Changing climatic conditions beginning of the Holocene 133 5.6.4 The warm African Humid Period 133 5.6.5 The termination of the African Humid Period 134 5.6.6 The Late Holocene 135 5.7 Garba Guracha – Climatic implications and driving mechanisms 136 5.7.1 Comparison of high and low altitudes in eastern Africa 136 5.7.2 Atmospheric circulation 138 5.8 References 144 6 Conclusions and Outlook 157 A Supplements to Chapter 2 162 B Supplements to Chapter 3 168 C Supplements to Chapter 4 173 D Supplements to Chapter 5 182 / While climate change and global warming are affecting eastern Africa today, the understanding of past climatic changes is limited. Especially during the last 15.000 years, eastern Africa has experienced spatially complex climatic changes. Although several paleoclimatic studies have been conducted in eastern Africa, reconstructing temperature changes and the hydrological history of lake archives, the driving mechanisms and teleconnections are yet not fully understood. A deeper understanding is precluded by (i) the lack of long, high-quality records of environmental change, especially in the Horn of Africa region, (ii) the lack of high altitude records, and (iii) insufficiently studied regions like eastern Ethiopia and Somalia. One of the region's most understudied high-altitude areas are the Bale Mountains, even though they encompass the continent's largest area above 4000 m a. s. l. This dissertation aims to further reduce the current lack of paleoclimatic reconstructions in high altitudes in the understudied Horn of Africa region. High-altitude perennial lakes, especially cirque lakes, are valuable archives for paleoclimate and environmental reconstructions, yielding continuous sedimentation undisturbed by human activity. The only perennial lake in the Bale Mountains, the Garba Guracha, lies in the afro-alpine zone at 3950 m a. s. l. Previous paleolimnological research revealed that Garba Guracha comprises a continuous paleoclimatic and environmental sedimentary record since the last deglaciation. In order to enhance the paleoclimatic knowledge of the Bale Mountains and hence of eastern Africa, new innovative proxies, e.g. brGDGTs, δ18Ofucose, δ18Odiatom, and δ2Hn alkane were applied to newly retrieved sediment cores of Garba Guracha. The application of these analyses and the interpretation of the results imply a deeper understanding of the retrieved sediment cores, concerning mainly sedimentology, chronology and organic matter source identification. The high resolution chronology of Garba Guracha, established using different dating methods and compounds (210Pb dating, radiocarbon dating of bulk sedimentary OM, compound class specific n alkanes, and charcoal), yields a basal age of ∼ 16 cal ka BP. The geochemical correlation of tephra layers in the Garba Guracha sediments to dated tephra layers of the region provides an external age control, further supporting the robustness of the new Garba Guracha chronology and the non existence of systematic age offsets. Similar ages obtained for n alkanes and bulk sediments suggest no pre aging of the biomarker in the very small afro-alpine catchment indicating short residence times or/and high aquatic productivity. Predominant autochthonous production of organic matter in the relative large lake compared to the catchment size has been proven by relatively low TOC/N ratios and relatively positive δ13C values. The aquatic origin of the sugar biomarker fucose is further supported by a methodological comparison of δ18Ofucose to a pure aquatic δ18Odiatom record. The good correlation and similar ranges of δ18Odiatom and δ18Ofucose (7.9 ‰ and 7.1 ‰, respectively) not only highlight the potential of δ18Osugar analyses in paleoclimatic studies but also lead to the conclusion that the Garba Guracha δ18Ofucose record reflects δ18Olake water. Therefore, without completely excluding the influence of the ‘amount effect’ and the ‘source-effect’, we interpret the record to reflect primarily the precipitation to evaporation ratio (P/E). The hydrological history of Garba Guracha is influenced by regional and northern hemisphere climatic changes. Precipitation increased at the onset of the Holocene, resulting in an overflowing lake between ∼ 10 and ∼ 7 cal ka BP (noted by the most negative δ18O values in the record). This humid phase corresponds to the African Humid Period (AHP), a spatially complex humid phase across equatorial and northern Africa, driven by enhanced West African Monsoon (WAM) and, in the case of the easterly-situated Bale Mountains, East African Monsoon (EAM) activity. While hydrological changes during the AHP in eastern Africa seem to be driven by meridional climatic processes, the high-altitude Garba Guracha archive shows additional similarities to reconstructed monsoonal changes in Oman. A continuous transition towards more positive δ18O values begins at 7 cal ka BP and indicates a gradual shift from humid to drier climate. The reconstructed temperature history is strongly linked to supraregional climatic changes associated with insolation forcing and the AHP, as well as with local anomalies associated with catchment deglaciation and hydrology. Cold temperatures prevailed in the high-altitude Garba Guracha until significant warming (3.0 °C in less than 600 years) occurred shortly after the Holocene onset. A thermal maximum prevailed between 9 and 6 cal ka BP, coinciding with humid conditions, followed by a temperature decrease until 1.4 cal ka BP. The temperatures at the Garba Guracha were reconstructed using a modified MBT'5ME calibration by adding 6 methyl brGDGT IIIa' (resulting in the MBT'5ME Bale Mountain index, r2 = 0.93, p < 0.05) due to an uncommon variation in 6 methyl brGDGTs in the modern lake surface sediment samples. The results of this dissertation reveal regional and global driving mechanisms of climatic changes in the Bale Mountains, further expanding paleoclimatic knowledge about the Horn of Africa. The innovative methodological approach of this thesis highlights the potential of δ18Osugar analyses and n alkane dating. Moreover, the results underline the need for intensified basic research like local brGDGT calibration studies to advance and specify existing scientific concepts.:1.1 Table of Content List of Abbreviations v List of Tables vi List of Figures vii List of papers ix Abstract x Zusammenfassung xii Acknowledgements xiv 1 Introduction 1 1.1 Motivation 2 1.2 Objectives of the thesis 5 1.3 Background – The Bale Mountains and biomarker 6 1.3.1 Study area and archive 6 1.3.2 A short introduction to selected biomarkers applied in environmental geochemistry 8 1.4 Methods used in the thesis 10 1.4.1 Monosaccharide sugar biomarkers 11 1.4.2 Total lipid extraction for n-alkane and brGDGTs analyses 11 1.4.3 Branched Glycerol Dialkyl Glycerol Tetraether analyses 12 1.4.4 Biogeochemical analyses 13 1.4.5 Radiocarbon dating 13 1.4.6 Age depth model 13 1.5 Structure of the thesis 15 1.6 References 16 2 Revisiting afro-alpine Lake Garba Guracha in the Bale Mountains of Ethiopia: rationale, chronology, geochemistry, and paleoenvironmental implications 27 Abstract 28 2.1 Introduction 29 2.1.1 Study site 29 2.2 Material and Methods 31 2.2.1 Chronology and dating 31 2.2.2 XRF scanning 34 2.2.3 Biogeochemical analyses 34 2.2.4 n-Alkane and sugar quantification 35 2.3 Results 35 2.3.1 The sedimentary sequence – Master core and lithofacies 35 2.3.2 Chronology 37 2.3.3 Geochemistry 39 2.4 Discussion 41 2.4.1 Chronology 41 2.4.2 Origin of organic matter 43 2.4.3 Environmental implications 45 2.4.4 Comparison with lake level and other records 49 2.5 Conclusions 50 2.6 Acknowledgements 50 2.7 References 51 3 The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms 61 Abstract 62 3.1 Introduction 62 3.1.1 Regional setting 64 3.2 Material and methods 66 3.2.1 Material and sampling 66 3.2.2 Compound-specific δ18O analyses of sugar biomarkers 66 3.2.3 δ18O analyses of diatoms 67 3.3 Results 68 3.3.1 δ18Ofuc record of Garba Guracha 68 3.3.2 δ18Odiatom record of Garba Guracha 69 3.4 Discussion 69 3.4.1 The Garba Guracha δ18Osugar record - lake or leaf water? 69 3.4.2 The Garba Guracha δ18Odiatom record 70 3.4.3 Comparison of reconstructed δ18Olake water from δ18Ofuc versus δ18Odiatom 71 3.4.4 Paleoclimatic significance and proxy interpretation 72 3.4.5 Comparison with other records 75 3.5 Conclusions 77 3.6 Acknowledgements 78 3.7 References 78 4 A Holocene temperature (brGDGT) record from Garba Guracha, a high-altitude lake in Ethiopia 89 Abstract 90 4.1 Introduction 90 4.1.1 Regional setting 93 4.2 Material and Methods 94 4.2.1 Material and Sampling 94 4.2.2 Sample preparation and analysis 95 4.2.3 BrGDGTs – structure, statistical methods and proxy calculation 96 4.2.4 Quantitative data analyses 97 4.3 Result 97 4.3.1 BrGDGT patterns of surface sediments from lakes in the Bale Mountains 97 4.3.2 BrGDGT patterns of the Garba Guracha sediment core 100 4.4 Discussion 103 4.4.1 Possible MAT calibration functions inferred from the expanded eastern African surface sediment dataset 103 4.4.2 Paleotemperature reconstructions for the Garba Guracha sedimentary record - comparison of the different calibrations 104 4.4.3 Paleotemperature reconstructions for the Garba Guracha sedimentary record – regional comparison 106 4.5 Conclusions 111 4.6 Acknowledgements 111 4.7 References 112 5 Synthesis 121 5.1 Sedimentation and chronology - What is the time frame and age depth function of the Garba Guracha core? 122 5.2 Source identification What is the origin of the organic material in the Garba Guracha sediment core? 125 5.3 Hydrology δ18O as a proxy for Garba Guracha evaporation history 126 5.4 Hydrology δ2H – as a proxy for the Garba Guracha precipitation history 128 5.5 Temperature - brGDGTs - as a proxy for Garba Guracha MAT history 129 5.6 Garba Guracha environmental and climate reconstruction – Why and how has the climate changed? 131 5.6.1 Deglaciation 132 5.6.2 North hemisphere forcings in the Garba Guracha catchment during the Younger Dryas period 132 5.6.3 Changing climatic conditions beginning of the Holocene 133 5.6.4 The warm African Humid Period 133 5.6.5 The termination of the African Humid Period 134 5.6.6 The Late Holocene 135 5.7 Garba Guracha – Climatic implications and driving mechanisms 136 5.7.1 Comparison of high and low altitudes in eastern Africa 136 5.7.2 Atmospheric circulation 138 5.8 References 144 6 Conclusions and Outlook 157 A Supplements to Chapter 2 162 B Supplements to Chapter 3 168 C Supplements to Chapter 4 173 D Supplements to Chapter 5 182

Thermokarst is a typical process that indicates widespread permafrost degradation in yedoma landscapes. The Lena-Aldan interfluvial area in Central Yakutia in eastern Siberia is now facing extensive landscape changes with surface subsidence due to thermokarst development during the past few decades. To clarify the spatial extent and rate of subsidence, multiple spatial datasets, including GIS and remote sensing observations, were used to analyze the Churapcha rural locality, which has a typical yedoma landscape in Central Yakutia. Land cover classification maps for 1945 and 2009 provide basic information on anthropogenic disturbance to the natural landscape of boreal forest and dry grassland. Interferometric synthetic aperture radar (InSAR) with ALOS-2/PALSAR-2 data revealed activated surface subsidence of 2 cm/yr in the disturbed area, comprising mainly abandoned agricultural fields. Remote sensing with an unmanned aerial system also provided high-resolution information on polygonal relief formed by thermokarst development at a disused airfield where InSAR analysis exhibited extensive subsidence. It is worth noting that some historically deforested areas have likely recovered to the original landscape without further thermokarst development. Spatial information on historical land-use change is helpful because most areas with thermokarst development correspond to locations where land was used by humans in the past. Going forward, the integrated analysis of geospatial information will be essential for assessing permafrost degradation.

Editorial on the Research Topic. Physics and Geomorphology of Sand Ripples on Earth and in the Solar System.

Dieser Beitrag beschreibt informatische Herausforderungen im Kontext eines Digital Humanities-Projekts zur Erschließung und Analyse historischer Wetteraufzeichnungen im Zeitraum 1774 - 1827. Bei der Erschließung der handschriftlichen Aufzeichnungen, die Besonderheiten wie numerische Messwerte in Tabellenstruktur und überlagernde Notizen enthalten, soll langfristig ein entsprechend trainierter OCR-Ansatz (optical character recognition) zum Einsatz kommen. Für die Erstellung entsprechender Trainingsdaten sowie für die manuelle Korrektur der automatisch erkannten Daten ergeben sich zunächst softwareergonomische Herausforderungen aus Perspektive der Medieninformatik. Der Fokus dieses Beitrags liegt daher auf der Erstellung von Tools unter Berücksichtigung von Prinzipien des usability engineering und des user-centered design (UCD) für geisteswissenschaftliche Forschungsvorhaben.

Spaceborne impact ionization mass spectrometers, such as the Cosmic Dust Analyzer on board the past Cassini spacecraft or the SUrface Dust Analyzer being built for NASA's upcoming Europa Clipper mission, are of crucial importance for the exploration of icy moons in the Solar System, such as Saturn's moon Enceladus or Jupiter's moon Europa. For the interpretation of data produced by these instruments, analogue experiments on Earth are essential. To date, thousands of laboratory mass spectra have been recorded with an analogue experiment for impact ionization mass spectrometers. Simulation of mass spectra of ice grains in space is achieved by a Laser Induced Liquid Beam Ion Desorption (LILBID) approach. The desorbed cations or anions are analyzed in a time-of-flight mass spectrometer. The amount of unstructured raw data is increasingly challenging to sort, process, interpret and compare with data from space. Thus far this has been achieved manually for individual mass spectra because no database containing the recorded reference spectra was available. Here we describe the development of a comprehensive, extendable database containing cation and anion mass spectra from the laboratory LILBID facility. The database is based on a Relational Database Management System with a web server interface and enables filtering of the laboratory data using a wide range of parameters. The mass spectra can be compared not only with data from past and future space missions but also mass spectral data generated by other, terrestrial, techniques. The validated and approved subset of the database is available for general public (https://lilbid-db.planet.fu-berlin.de).

Assessment of potentially contaminated sites (PCS) can be expensive; hence, simple and less demanding methods and models are required. This work attempts to provide an approach that can aid in selecting the most appropriate model for the PCS. The developed method uses over 100 field site data to evaluate four test models (analytical/empirical) that provide the maximum plume length (Lmax), which is used as a principal model ranking quantity in this work. Analysis of site data shows that field plume length (Lf) follows a log-normal distribution. Subsequently, Lmax is delineated with respect to Lf using a threshold probability as underestimating, overestimating, and overly-overestimating. Akaike information criterion (AIC) and analytical hierarchy process (AHP) are considered to support the threshold approach results. The classical AIC is modified (to AICmod) to fit the term represented by the difference between Lf and Lmax. Additionally, the threshold factors as a product of subjective weights are added to the AICmod. Using Lf and Lmax, the AICmod provides a distinct ranking of the test models. For the AHP approach, the goodness of fit, underestimation, overly overestimation, and model complexity are the four chosen criteria. Similar to AICmod, the AHP approach provides a distinct ranking of the test models. The final decision on the best fitting model can be made on user criteria following the scheme developed in this work.

Nanofiltration (NF) is an attractive option for the treatment of wastewater e.g. municipal wastewater and landfill leachate. However, membrane fouling can be a major obstacle in the implementation of this technology. Fouling of nanofiltration membranes by hu-mic acids (HA) was investigated using bisphenol A (BPA) as an indicator chemical to dif-ferentiate between various mechanisms that may lead to a change in solute rejection. Three commercially available NF membranes were investigated and an accelerated foul-ing condition was achieved with a foulant mixture containing humic acids in an electro-lyte matrix. The effects of membrane fouling on the rejection of BPA were interpreted with respect to the membrane pore sizes and the fouling characteristics. Results report-ed here indicate that calcium concentration in the feed solution could be a major factor governing the humic acid fouling process. Moreover, a critical concentration of calcium in the feed solution was observed, at which membrane fouling was most severe. Mem-brane fouling characteristics were observed by their influence on BPA rejection. Such influence could result in either an increase or decrease in rejection of BPA by the three different membranes depending on the rejection mechanisms involved. It is hypothe-sised that these mechanisms could occur simultaneously and that the effects of each might not be easily distinguished. However, it was observed that their relative contribu-tion was largely dependent upon membrane pore size. Pore blocking, which resulted in a considerable improvement in rejection, was prominent for the more open pore size TFC-SR2 membrane. In contrast, the cake-enhanced concentration polarisation (CECP) effect was more severe for the tighter NF270 and NF90 membranes. For hydrophobic solutes such as BPA, the formation of the fouling layer could also interfere with the so-lute-membrane interaction, and therefore, exert considerable influence on the separa-tion process. The combined impact of humic acid fouling and CaCO3 scaling on the rejection of trace organic contaminants by a commercially available nanofiltration membrane was inves-tigated in this study. Due to the presence of humic acid in the feed solution, CaCO3 scal-ing behaviour differed substantially from that of a pure CaCO3 solution. A prolonged induction period was consistently observed prior to the onset of membrane scaling. In addition, membrane scaling following humic acid fouling did not result in a complete loss of permeate flux. This is consistent with the absence of any large CaCO3 crystals. In fact, the CaCO3 crystals on the membrane surface were quite small and similar in size, which would result in a relatively porous cake layer. At the onset of CaCO3 scaling the rejection of all three trace organic contaminants started to decrease dramatically. The observed decrease in rejection of the trace organic contaminants was much more se-vere than that reported previously with a single layer of either organic or colloidal foul-ing. Such severe decrease in rejection can be attributed to the extended cake-enhanced concentration polarisation effect occurring as a result of the combination of membrane fouling and scaling. The porous CaCO3 scaling layer could lead to a substantial cake-enhanced concentration polarisation effect. In addition, the top CaCO3 scaling layer could reduce the wall shear rate within the underlying humic acid fouling layer, causing an additional concentration polarisation (CP) effect.:1 INTRODUCTION 1 1.1 Fundamentals of NF/RO 1 1.1.1 Solute transport through NF/RO membranes 2 1.1.2 Separation mechanisms 3 1.1.2.1 Steric size exclusion 3 1.1.2.2 Donnan effect 3 1.1.2.3 Electrostatic repulsion 4 1.1.2.4 Adsorption 4 1.1.3 Environmental applications of NF/RO 5 1.1.4 Drinking water treatment from groundwater and surface water sources 5 1.1.5 Water/Wastewater reclamation 7 1.2 Classification and materials of NF/RO membranes 7 1.2.1 Membrane classes 7 1.2.2 Membrane materials 8 1.2.3 Organic membrane materials 9 1.2.3.1 Polyamide membranes 9 1.2.3.2 Cellulose acetate membranes 9 1.2.4 Inorganic membrane materials 10 1.3 Removal of trace organic contaminants 11 1.3.1 Impact of membrane characteristics 14 1.3.1.1 Molecular weight cut-off/pore size 14 1.3.1.2 Surface charge 14 1.3.1.3 Hydrophobicity/hydrophilicity 15 1.3.1.4 Surface morphology 15 1.3.2 Impact of feed characteristics 17 1.3.2.1 pH value 17 1.3.2.2 Ionic strength 18 1.3.2.3 Organic matter 19 1.3.2.4 Presence of divalent ions 20 1.3.2.5 Presence of foulants 20 1.3.2.6 Temperature 20 1.3.3 Impact of solute characteristics 22 1.3.3.1 Molecular weight 22 1.3.3.2 Molecular size (length and width)/molecular volume 22 1.3.3.3 Minimum projection area/Equivalent width 23 1.3.3.4 Charge 23 1.3.3.5 Hydrophobicity/hydrophilicity 24 1.3.4 Impact of operational characteristics 25 1.3.4.1 Transmembrane pressure/permeate or transmembrane flux 25 1.3.4.2 Cross-flow velocity/recovery/concentration polarisation 25 1.3.5 Impact of fouling on rejection 26 1.3.5.1 Organic fouling 28 1.3.5.2 Colloidal fouling 30 1.3.5.3 Inorganic fouling (scaling) 31 1.3.5.4 Biological fouling 32 1.3.6 Impact of membrane cleaning on rejection 32 1.3.6.1 Changes of membrane morphology due to cleaning 32 1.3.6.2 Impact on rejection of TrOCs due to cleaning 33 1.3.7 Validation at pilot and full scale systems 35 2 MEMBRANE FOULING IN THE NANOFILTRATION OF LANDFILL LEACHATE AND ITS IMPACT ON TRACE CONTAMINANT REMOVAL 37 2.1 Introduction 37 2.2 Materials and Methods 40 2.2.1 Analytical reagents and chemicals 40 2.2.2 Nanofiltration membrane 40 2.2.3 Membrane filtration set-up and protocol 41 2.2.4 Analytical technique 42 2.3 Results and discussion 42 2.3.1 Landfill leachate characterisation 42 2.3.2 Physico-chemical properties of bisphenol A 43 2.3.3 Influence of the calcium concentration on the flux 44 2.3.4 Influence of fouling on the rejection of organic contaminants 46 2.4 Conclusions 48 3 CHARACTERISING HUMIC ACID FOULING OF NANOFILTRATION MEMBRANES USING BISPHENOL A AS A MOLECULAR INDICATOR 50 3.1 Introduction 50 3.2 Materials and methods 52 3.2.1 Model NF membranes and membrane characterisation 52 3.2.2 Model trace organic contaminant 52 3.2.3 Organic foulant 53 3.2.4 Membrane filtration set-up 54 3.2.5 Filtration protocol 55 3.2.6 Analytical technique 56 3.3 Results and discussions 56 3.3.1 Membrane characteristics 56 3.3.2 Membrane fouling behaviour 58 3.3.3 Change of membrane hydrophobicity 61 3.3.4 Effects of organic fouling on the nanofiltration of BPA 63 3.3.5 Effects of organic fouling on rejection: the mechanisms 65 3.4 Conclusions 67 4 EFFECTS OF FOULING AND SCALING ON THE REJECTION OF TRACE ORGANIC CONTAMINANTS BY A NANOFILTRATION MEMBRANE: THE ROLE OF CAKE-ENHANCED CONCENTRATION POLARISATION 69 4.1 Introduction 69 4.2 Materials and methods 71 4.2.1 Nanofiltration membrane 71 4.2.2 Chemicals and reagents 71 4.2.3 Crossflow membrane filtration system 72 4.2.4 Experimental protocol 73 4.2.5 SEM-EDS analysis 74 4.2.6 Analytical methods 75 4.3 Results and discussion 75 4.3.1 Membrane characteristics 75 4.3.2 Membrane fouling and scaling development 76 4.3.3 Effects of fouling/scaling on the membrane rejection behaviour 79 4.3.4 Cake-enhanced concentration polarisation 85 4.4 Conclusions 87 5 SUMMARY AND CONCLUSIONS 88 6 REFERENCES 94 7 ACKNOWLEDGEMENTS 112

Diese Schriftenreihe präsentiert eine strukturgeologische Neubewertung des Sächsischen Granulitgebirges, die aus einem multidisziplinären Datensatz abgeleitet wird. Die gewonnenen Ergebnisse münden in die Darstellung einer Bruchtektonischen Karte des Granulitgebirges und einen zusammenfassenden Katalog der Bruchstrukturen. Hierbei liegt ein Schwerpunkt des Projektes auf der Identifikation und Charakterisierung junger Störungszonen. Die Veröffentlichung richtet sich sowohl an geologisch interessierte Laien ohne fachlichen Hintergrund als auch an ein Fachpublikum. Redaktionsschluss: 31.10.2021