Central Asia is highly vulnerable to large earthquakes, yet existing records of past seismic activity in this area are still insufficient to reliably assess regional earthquake hazard on longer timescales. Within this study, the sediments of Sary Chelek, a mountain lake in the western Kyrgyz Tian Shan, were investigated to explore its potential as a natural paleoseismic archive. The lacustrine deposits are characterized by a succession of annually laminated (varved) sediments overlying event deposits that consist of large-scale turbidites and distorted lake sediments, similar to earthquake-related deposits described from other lake sediment records. Microscopic sediment analysis furthermore revealed distorted varves in the laminated sequence that closely resemble earthquake-related soft-sediment deformation structures. Varve counting and radiometric dating determine the formation of the distorted varves and the emplacement of the large-scale event deposits to the early 1990s and mid-1940s, respectively. This is in good temporal agreement with the occurrence of two large earthquakes that struck western Kyrgyzstan in AD 1992 and AD 1946. These results and particularly the precise age control of the Sary Chelek sediment record highlight its potential for establishing a long and precisely dated record of regional earthquake activity.

Tajikistan is often affected by atmospheric mineral dust. The direct and indirect radiative effects of dust play a sensitive role in the climate system in Central Asia. The Central Asian Dust Experiment (CADEX) provides first lidar measurements in Tajikistan. The autonomous multiwavelength polarization Raman lidar Polly(XT) was operated for 1.5 years (2015/16) in Dushanbe. In spring, lofted layers of long-range transported dust and in summer/autumn, lower laying dust from local or regional sources with large optical thicknesses occurred.

Lake Sihailongwan in Jilin province, NE China, provides the first continuous and almost entirely seasonally laminated sediment record on the East Asian mainland comprising the complete Holocene, the Late-glacial period, and large parts of the Last Glacial. Sediment and palynological proxy data provide a finely resolved regional environmental history of the East Asian monsoon. A varve-based chronology (shl-vc2) has been established for the last 65,000 years and allows a detailed comparison with other long regional and global palaeoclimate records. Vegetation density of the study area depends, on the long run, on precessionally forced insolation changes, with superimposed millennial-scale variability during the Last Glacial. Periodic increase of organic carbon content and thermophilous tree species like Ulmus and Fraxinus and contemporary decrease of shrub Alnus precisely mirror millennial-scale climatic variations primarily known from Greenland ice-cores as Dansgaard-Oeschger cycles, as well as Late-glacial period climate changes. Percentages of trees & shrubs pollen and in particular lake productivity-related data reveal substantial differences between interstadial intensities, with those between 50 and 60 ka BP being more pronounced than the following ones.

Mineral dust needs to be characterized comprehensively since it contributes to the climate change in Tajikistan / Central Asia. Lidar results from the measurements of mineral dust during CADEX are compared with results of sun photometer measurements, satellite-based measurements, and chemical analysis of ground samples. Although the dust is often advected from far-range sources, it impacts on the local conditions considerably.

The production of gas from unconventional resources became an important position in the world energy economics. In 2012, the European Commission's Joint Research Centre estimate 16 trillion cubic meters (Tcm) of technically recoverable shale gas in Europe. Taking into account that the exploitation of unconventional gas can be accompanied by serious health risks due to the release of toxic chemical components and natural occurring radionuclides into the return flow water and their near-surface accumulation in secondary precipitates, we investigated the release of U, Th and Ra from black shales by interaction with drilling fluids containing additives that are commonly employed for shale gas exploitation. We performed leaching tests at elevated temperatures and pressures with an Alum black shale from Bomholm, Denmark and a Posidonia black shale from Lower Saxony, Germany. The Alum shale is a carbonate free black shale with pyrite and barite, containing 74.4 mu g/g U. The Posidonia shales is a calcareous shale with pyrite but without detectable amounts of barite containing 3.6 mu g/g U. Pyrite oxidized during the tests forming sulfuric acid which lowered the pH on values between 2 and 3 of the extraction fluid from the Alum shale favoring a release of U from the Alum shale to the fluid during the short-term and in the beginning of the long-term experiments. The activity concentration of U-238 is as high as 23.9 mBq/ml in the fluid for those experiments. The release of U and Th into the fluid is almost independent of pressure. The amount of uranium in the European shales is similar to that of the Marcellus Shale in the United States but the daughter product of U-238, the Ra-226 activity concentrations in the experimentally derived leachates from the European shales are quite low in comparison to that found in industrially derived flowback fluids from the Marcellus shale. This difference could mainly be due to missing Cl in the reaction fluid used in our experiments and a lower fluid to solid ratio in the industrial plays than in the experiments due to subsequent fracking and minute cracks from which Ra can easily be released.

For the first time, continuous vertically resolved aerosol measurements were performed by lidar in Tajikistan, Central Asia. Observations with the multiwavelength polarization Raman lidar PollyXT were conducted during CADEX (Central Asian Dust EXperiment) in Dushanbe, Tajikistan, from March 2015 to August 2016. Co-located with the lidar, a sun photometer was also operated. The goal of CADEX is to provide an unprecedented data set on vertically resolved aerosol optical properties in Central Asia, an area highly affected by climate change but largely missing vertically resolved aerosol measurements. During the 18-month measurement campaign, mineral dust was detected frequently from ground to the cirrus level height. In this study, an overview of the measurement period is given and four typical but different example measurement cases are discussed in detail. Three of them are dust cases and one is a contrasting pollution aerosol case. Vertical profiles of the measured optical properties and the calculated dust and non-dust mass concentrations are presented. Dust source regions were identified by means of backward trajectory analyses. A lofted layer of Middle Eastern dust with an aerosol optical thickness (AOT) of 0.4 and an extinction-related Ångström exponent of 0.41 was measured. In comparison, two near-ground dust cases have Central Asian sources. One is an extreme dust event with an AOT of 1.5 and Ångström exponent of 0.12 and the other one is a most extreme dust event with an AOT of above 4 (measured by sun photometer) and an Ångström exponent of −0.08. The observed lidar ratios (and particle linear depolarization ratios) in the presented dust cases range from 40.3 to 46.9 sr (and 0.18–0.29) at 355 nm and from 35.7 to 42.9 sr (0.31–0.35) at 532 nm wavelength. The particle linear depolarization ratios indicate almost unpolluted dust in the case of a lofted dust layer and pure dust in the near-ground dust cases. The lidar ratio values are lower than typical lidar ratio values for Saharan dust (50–60 sr) and comparable to Middle Eastern or west-Asian dust lidar ratios (35–45 sr). In contrast, the presented case of pollution aerosol of local origin has an Ångström exponent of 2.07 and a lidar ratio (particle linear depolarization ratio) of 55.8 sr (0.03) at 355 nm and 32.8 sr (0.08) at 532 nm wavelength.

Dust influences climate and weather by direct and indirect radiative effects or heterogeneous ice nucleation. Dust is often transported to and across Tajikistan. Tajikistan and all other countries in Central Asia suffer from climate change and the potential role of dust in that climate change needs to be investigated and quantified. Therefore the Central Asian Dust EXperiment (CADEX) conducted first lidar observations in Tajikistan for long-term vertically resolved aerosol measurements with the multiwavelength polarization Raman lidar PollyXT from March 2015–August 2016. A measurement example of a polluted dust layer as well as mean values of intensive optical properties and the aerosol optical thickness measured during the months August 2015 and August 2016 are shown.

Dust influences climate and weather by direct and indirect radiative effects or heterogeneous ice nucleation. Dust is often transported to and across Tajikistan. Tajikistan and Central Asia suffer from climate change and the potential role of dust needs to be investigated. But up to now, only a small number of measurements are available in that region, especially no vertical profiles of aerosol optical properties are known. Therefore the Central Asian Dust EXperiment (CADEX) conducts first lidar measurements in Tajikistan for long-term vertically resolved aerosol measurements from March 2015–September 2016. The multiwavelength polarization Raman lidar PollyXT is used for these measurements. Two characteristic measurement examples of dust layers are presented in this contribution.

We report about first aerosol lidar measurements that were performed in Dushanbe, Tajikistan (Central Asia) during our Central Asian Dust EXperiment (CADEX) project. The determined intensive property depolarization ratio allows an aerosol characterization and often shows mineral dust at lofted layers during spring time and optically and geometrically thick layers that touch the surface during summer time. The intensive property lidar ratio shows lower values for Asian dust than the lidar ratios measured from Saharan dust during our former campaigns in Morocco and Cape Verde. We show one measurement example from CADEX, allocate the possible dust source area for this measurement and discuss the measured differences between Asian and Saharan dust.

Ca–Na partitioning between tourmaline and a coexisting fluid is investigated in the system CaO–Na2O–B2O3–Al2O3–MgO–SiO2–H2O–Cl between 0.2–4.0 GPa and 500–700 °C. The synthesis experiments produced a mineral assemblage of tourmaline, coesite/quartz, and in some cases additional phases, typically comprising <1 wt% of the solid product. The synthesized tourmalines are solid solutions of dravite [NaMg3Al6Si6O18(BO3)3(OH)3(OH)], “oxy-uvite” (i.e. “Ca–Mg–O root name”) [CaMg3Al6Si6O18(BO3)3(OH)3O], and magnesio-foitite [☐(Mg2Al)Al6Si6O18(BO3)3(OH)3(OH)]. Starting materials comprised a fluid of constant ionic strength (2.00 m) and an oxide mixture with a constant Mg/Al ratio. As a result, the number of vacancies at the X site and the Mg/Al ratio of tourmaline crystals synthesized at the same temperature vary only slightly. The major solid solution is Ca–Na exchange at the X site via the exchange vector X Ca W O[ X Na W (OH)]−1, with the exchange vector X (Ca☐)[ X Na2]−1 serving as a secondary Ca-incorporation mechanism. Tourmaline’s X-site composition reflects the fluid composition, whereby the Ca (or Na) concentration in the fluid corresponds with the Ca (or Na) content in tourmaline at each pressure and temperature. At 0.2 GPa, 700 °C, Ca preferentially partitions into tourmaline, producing the most Ca-rich tourmaline crystals synthesized here. At pressures >1.0 GPa, Ca partitions preferentially into the fluid, resulting in Na-dominant tourmaline compositions. Temperature has a secondary effect on Ca–Na partitioning, with higher temperatures correlating with increased Ca incorporation in tourmaline. Based on the experimental findings, tourmaline is expected to have Ca-rich compositions when it forms in low pressure, high-temperature Ca-rich rocks, consistent with the current record of tourmaline occurrence. The bulk Mg/Al ratio and the pH of the tourmaline-forming system may also affect Ca incorporation in tourmaline, but remain to be investigated experimentally.

Tourmaline was synthesized in the system MgO–Al2O3–B2O3–SiO2–KCl–NaCl–H2O from an oxide mixture and excess fluid at 500–700 °C and 0.2–4.0 GPa to investigate the effect of pressure, temperature, and fluid composition on the relative incorporation of Na and K in dravitic tourmaline. Incorporation of K at the X-site increases with pressure, temperature, and KCl concentration; a maximum of 0.71 K pfu (leaving 0.29 X-vacant sites pfu) was incorporated into K-dravite synthesized at 4.0 GPa, 700 °C from a 4.78 m KCl, Na-free fluid. In contrast, Na incorporation depends predominately on fluid composition, rather than pressure or temperature; dravite with the highest Na content of 1.00 Na pfu was synthesized at 0.4 GPa and 700 °C from a 3.87 m NaCl and 1.08 m KCl fluid. All synthesized crystals are zoned, and the dominant solid solution in the Na- and K-bearing system is between magnesio-foitite [□(Mg2Al)Al6Si6O18(BO3)3(OH)3OH] and dravite [NaMg3Al6Si6O18(BO3)3(OH)3(OH)], with the dravitic component increasing with the concentration of Na in the fluid. In the K-bearing, Na-free system, the dominant solid solution is between magnesio-foitite and K-dravite [KMg3Al6Si6O18(BO3)3(OH)3(OH)], with the K-dravitic component increasing with pressure, temperature, and the concentration of K in the fluid. The unit-cell volume of tourmaline increases with K incorporation from 1555.1(3) to 1588.1(2) Å3, reflecting the incorporation of the relatively large K+ ion. Comparison of our results to the compositional data for maruyamaite (K-dominant tourmaline) from the ultrahigh-pressure rocks of the Kokchetav Massif in Kazakhstan suggests that the latter was formed in a K-rich, Na-poor environment at ultrahigh-pressure conditions near the diamond-stability field.

We present the results of our investigations on the radiocarbon dated core sediments from the Lake Tso Moriri, NW Himalaya aimed at reconstructing palaeohydrological changes in this climatically sensitive region. Based on the detailed geochemical, mineralogical and sedimentological analysis, we recognise several short-term fluctuations superimposed upon seven major palaeohydrological stages identified in this lake since similar to 26 cal ka. Stage I (>20.2 cal ka): shallow lake characterised by input of coarse-grained detrital sediments; Stage II (20.2-16.4 cal ka): lake deepening and intensification of this trend ca. 18 cal ka; Stage III (16.4-11.2 cal ka): rising lake levels with a short term wet phase (13.1-11.7 cal ka); Stage IV (11.2-8.5 cal ka): early Holocene hydrological maxima and highest lake levels inferred to have resulted from early Holocene Indian monsoon intensification, as records from central Asia indicate weaker westerlies during this interval; Stage V (8.5-5.5 cal ka): mid-Holocene climate deterioration; Stage VI (5.5-2.7 cal ka): progressive lowering of lake level; Stage VII (2.7-0 cal ka): onset of modern conditions. The reconstructed hydrological variability in Lake Tso Moriri is governed by temperature changes (meltwater inflow) and monsoon precipitation (increased runoff). A regional comparison shows considerable differences with other palaeorecords from peninsular India during late Holocene. (C) 2014 Elsevier Ltd and INQUA. All rights reserved.

The Aral Sea has been shrinking since 1963 due to extensive irrigation and the corresponding decline in the river water inflow. Understanding of the current hydrological situation demands an improved understanding of the surface water/groundwater dynamics in the region. Rn-222 and Ra-226 measurements can be used to trace groundwater discharge into surface waters. Data of these radiometric parameters were not previously available for the study region. We determined Rn-222 activities after liquid phase extraction using Liquid Scintillation Counting (LSC) with peak-length discrimination and analyzed Ra-226 concentrations in different water compartments of the Amu Darya Delta (surface waters, unconfined groundwater, artesian water, and water profiles from the closed Large Aral Sea (western basin).The water samples comprise a salinity range between 1 and 263 g/l. The seasonal dynamics of solid/water interaction under an arid climate regime force the hydrochemical evolution of the unconfined groundwater in the Amu Darya Delta to high-salinity Na(Mg)Cl(SO4) water types. The dissolved radium concentrations in the waters were mostly very low due to mineral over-saturation, extensive co-precipitation of radium and adsorption of radium on coexisting solid substrates.The analysis of very low Ra-226 concentrations (<10 ppq) at remote study sites is a challenge. We used the water samples to test and improve different analytical methods. In particular, we modified a procedure developed for the alpha-spectrometric determination of Ra-226 after solid phase extraction of radium using 3M Empore(TM) High Performance Extraction Disks (Purkl, 2002) for the analysis of the radionuclide using an ICP sector field mass spectrometer. The Ra-226 concentration of 17 unconfined groundwater samples ranged between 0.2 and 5 ppq, and that of 28 artesian waters between <0.2 and 13 ppq. The ICP-MS results conformed satisfactorily to analytical results based on gamma-measurements of the Rn-222 ingrowth after purging and trapping on super-cooled charcoal. The Ra-226 concentrations were positively correlated with the salinity and the dissolved NaCl concentrations. The occurrence of unusually high Ra-226 activities is explained by radium release from adsorption sites with increasing salinity. The inferred spatial variability of Rn-222 in the Aral Sea and of Rn-222 and Ra-226 in the groundwater of the Amu Darya Delta is discussed in the context of our own previous hydrochemical studies in the study sites. Relatively low Rn-222 activities in the unconfined GW (1-9.5 Bq/l) indicate the alluvial sediments hosting the GW to be a low-U-238(Ra-226) substrate. Positive correlations between U and Ra-226, and U and Rn-222 are likely related to locally deposited Fe(Mn)OOH precipitates. The Rn-222 activity of the GW, however, distinctly exceeds the Rn-222 concentration in the Aral Sea (10 mBq/l), in principle, making Rn-222 a sensitive tracer for the inflow of GW. The high water volume of the Large Aral Sea and wind induced mixing of its water body, however, hamper the detection of local groundwater inflow. (C) 2015 Elsevier Ltd. All rights reserved.

From November 2006 to January 2010, a sediment trap that was cleared monthly was deployed in Lake Challa, a deep stratified freshwater lake on the eastern slope of Mt. Kilimanjaro in southern Kenya. Geochemical data from sediment trap samples were compared with a broad range of limnological and meteorological parameters to characterize the effect of single parameters on productivity and sedimentation processes in the crater basin. During the southern hemisphere summer (November—March), when the water temperature is high and the lake is biologically productive (nondiatom algae), calcite predominated in the sediment trap samples. During the “long rain” season (March—May) a small amount of organic matter and lithogenic material caused by rainfall appeared. This was followed by the cool and windy months of the southern hemisphere winter (June—October) when diatoms were the main component, indicating a diatom bloom initiated by improvement of nutrient availability related to upwelling processes. The sediment trap data support the hypothesis that the light—dark lamination couplets, which are abundant in Lake Challa cores, reflect seasonal delivery to the sediments of diatom‐rich particulates during the windy months and diatom‐poor material during the wet season. However, interannual and spatial variability in upwelling and productivity patterns, as well as El Niño—Southern Oscillation (ENSO)‐related rainfall and drought cycles, exert a strong influence on the magnitude and geochemical composition of particle export to the hypolimnion of Lake Challa.

We report the results of our investigations on the catchment area, lake surface sediments, and hydrology of the high altitude alpine Tso Moriri Lake, NW Himalayas (India). Our results indicate that the lake is currently alkaline, and thermally stratified with an oxic bottom layer. Results from hydrochemistry and isotopic composition (delta O-18 and delta D) of inflowing streams and lake waters show that Tso Moriri Lake is an evaporative lake with contributions from both westerly source (snow melt) and Indian summer monsoon precipitation. Geochemical and mineralogical investigations on the catchment and lake surface sediments reveal the presence of authigenic aragonite in modern lake sediment. The lithogenic components reflect the inflow and sorting processes during transport into the lake, whereas the authigenic carbonate fraction can be linked to the changes in ([precipitation+meltwater]/evaporation) (I/E) balance within the lake. The spatial variability in grain size distribution within the lake surface sediments shows that the grain size data can be utilised as a proxy for transport energy and shoreline proximity in the lake basin. We have evaluated the applicability of commonly applied environmentally sensitive proxies (isotopes, mineralogy, weathering indices) for palaeoenvironmental reconstruction in the Tso Moriri Lake. Our results show that the commonly used weathering index (Rb/Sr) is not applicable due to Sr contribution from authigenic carbonates. The useful weathering indices in Tso Moriri Lake are the Si/Al and the Chemical Proxy of Alteration (CPA). Since the carbonates are formed by evaporative processes, their presence and isotopic values can be used as indicators of I/E changes in the lake.

A dust monitoring program was initiated in the summer of 2010 to (i) improve the informative value of aeolian components of varved lake sediments in Central Asia for palaeoclimatic interpretations, (ii) evaluate the impact of aeolian influx on modern lakes in the region and (iii) obtain data for a future comparison with dust east of the high mountain belt formed by the Alay, Pamir, Tien Shan and Altai mountains. We collected the coarse (>2.5 mu m) dust fraction on the northern slopes of the Tien Shan 42 degrees 40'49.69"N, (74 degrees 41'37.36"E, 1740 m asl) using a high-volume slit-impactor at 3-day sampling intervals. We present data on the mineralogical composition, particle-size distribution, soluble salts and nitrate isotope composition of the collected dust. The short-term and seasonal changes in dust concentration and composition are discussed in the context of high temporal resolution measurements of meteorological parameters and particle counts for 31 grain-size bands.Throughout the study period, CaCO3 was a major dust constituent (average particle frequency 14%). Between July 2010 and October 2012, the average content of soluble salts was 10 wt.%; mole percentages of water-leachable anions were 60% NO3, 30% SO4, 10% Cl. Ca was the dominant leachable cation (>90%). The collected dust comprised (i) gypsum which forms pedogenically in the topsoils of arid regions and (ii) secondary gypsum originating from the interaction of sulphuric acid aerosols with CaCO3 in the atmosphere. Variable proportions of (i) and (ii) and the extent of Ca(NO3)2 formation (verified by chemical mass budgets) were documented in the Ca/Sr and Ca/SO4 ratios of the aqueous leachates.The isotopic compositions of the dust nitrate in the majority of the samples clustered between 10 and +10%0 for delta N-15[NO3] (VSMOW) and +50 and +100%0 for delta O-18[NO3] (Air). The delta O-18[NO3] values of a majority of the collected samples exhibited a weak positive correlation with the NO3 load of the collected dust (R-2 = 0.148). The time series of the delta N-15[NO3] values varied around a basement level of -6%0, which indicates that NO from mobile sources is a major precursor of the dust-NO3. The distinct, positive departures from these values correlated with increases in the content of soot. We conclude that the related delta N-15[NO3] peaks reflect increased NOx, contributions from coal burning. The possible origin of the dust was evaluated using satellite images and backward trajectory calculations for a few example monitoring intervals. Data synthesis in the context of hemispherical atmospheric circulation models, including the data for 2013, the results from ongoing chemical and isotope analyses of the non-soluble solid residues of the collected materials and the statistical handling of an extended data set will further elucidate the relationships involving atmospheric circulation, atmospheric dust load, dust sources and the characteristics of the study region. (c) 2014 Elsevier Ltd. All rights reserved.

We examine mid- to late Holocene centennial-scale climate variability in Ireland using proxy data from peatlands, lakes and a speleothem. A high degree of between-record variability is apparent in the proxy data and significant chronological uncertainties are present. However, tephra layers provide a robust tool for correlation and improve the chronological precision of the records. Although we can find no statistically significant coherence in the dataset as a whole, a selection of high-quality peatland water table reconstructions co-vary more than would be expected by chance alone. A locally weighted regression model with bootstrapping can be used to construct a ‘best-estimate’ palaeoclimatic reconstruction from these datasets. Visual comparison and cross-wavelet analysis of peatland water table compilations from Ireland and Northern Britain show that there are some periods of coherence between these records. Some terrestrial palaeoclimatic changes in Ireland appear to coincide with changes in the North Atlantic thermohaline circulation and solar activity. However, these relationships are inconsistent and may be obscured by chronological uncertainties. We conclude by suggesting an agenda for future Holocene climate research in Ireland.