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Rationale: Preparation of BaSO4 from samples of atmospheric rain, snow, and aerosols has been used for δ18O and δ34S analyses. In the present study, we investigated the effect of various sample pretreatments on δ18O and δ34S values determined from a Na2SO4 reagent solution and samples of atmospheric precipitation to improve assay time and cost efficiency. Methods: BaSO4 was prepared from a Na2SO4 solution by (a) evaporative concentration, (b) evaporation to dryness, (c) evaporation to dryness after adding HCl, and (d) evaporation to concentration after adding HCl, followed by cooling and then precipitation using a BaCl2 solution. To analyze the atmospheric precipitation samples for δ18O, BaSO4 prepared from the samples was treated with diethylenetriaminepentaacetic acid (DTPA) and SO42− and separated chromatographically. The values of δ18O and δ34S were measured using a continuous‐flow elemental analyzer coupled to an isotope‐ratio mass spectrometer. Results: The δ34S values in BaSO4 precipitated from Na2SO4 solution determined by methods (a)–(c) were consistent within precisions of ±0.5‰. The δ18O values of methods (a) and (b) were consistent within ±0.2‰, whereas the δ18O values of methods (c) and (d) increased with increasing HCl concentrations. Similar results were obtained from samples of atmospheric precipitations. The δ18O values from DTPA‐treated BaSO4 were consistent with those obtained by chromatographic separation within ±0.5‰. Conclusions: We found no significant differences in the effects of various pretreatments (acidification, heating, concentration, and drying) on δ18O and δ34S values in sulfate from samples of atmospheric precipitation and aerosols extracted as BaSO4 if HCl was not added to the sample before heating and BaSO4 was treated with DTPA for the δ18O analysis. [ABSTRACT FROM AUTHOR]

This study investigated a continuous sediment core, retrieved from the deepest part in Lake Hovsgol, northwestern Mongolia. Its surrounds are occupied by a continuous Siberian permafrost zone. Distinct geochemical and lithological features suggest that the watershed soil was moistened during the last deglaciation, associated with climate amelioration. Especially, the calcareous glacial clay layers (ca 13.7 and ca 11.0 cal. ka BP), with high sulfur content peaks and positive shifts of δ34S values, well correlate with the timing of meltwater pulses 1A and 1B, leading to rapid warming such as Bølling/Allerød and Preboreal Holocene, respectively. This finding allows our interpretation for the calcareous glacial clay layers produced by landslide‐induced debris flow, which resulted from intensive water discharge from rapid thawing of permafrost during the abrupt warming periods. Our correlation with Lake Baikal records suggests that these permafrost thawings have accelerated over the area of the Selenga drainage basin (continental interior Eurasia). Key Points: The high TS contents with positive δ34S anomalies in sediments of lakes in permafrost zones become an indicator of permafrost thawingRapid thawing of Siberian permafrost during the last deglaciation occurred over the Selenga drainage basin (continental interior Eurasia)Thawing of Siberian permafrost was accelerated at ca 13.7 and ca 11.0 cal. ka BP, which correspond to Bølling/Allerød and Preboreal Holocene [ABSTRACT FROM AUTHOR]

Micro‐X‐ray fluorescence scanning spectroscopy of marine and lake sedimentary sequences can provide detailed palaeoenvironmental records through element intensity proxy data. However, problems with the effects of interstitial pore water on the micro‐X‐ray fluorescence intensities have been pointed out. This is because the X‐ray fluorescence intensities are measured directly at the surfaces of split wet sediment core samples. This study developed a new method for correcting X‐ray fluorescence data to compensate for the effects of pore water using a scanning X‐ray analytical microscope. This involved simultaneous use of micro‐X‐ray fluorescence scanning spectroscopy and an X‐ray transmission detector. To evaluate the interstitial pore water content from the X‐ray transmission intensities, a fine‐grained sediment core retrieved from Lake Baikal (VER99‐G12) was used to prepare resin‐embedded samples with smooth surfaces and uniform thickness. Simple linear regression between the linear absorption coefficients of the samples and their porosity, based on the Lambert–Beer law, enabled calculation of the interstitial pore spaces and their resin content with high reproducibility. The X‐ray fluorescence intensities of resin‐embedded samples were reduced compared with those of dry sediment samples because of: (i) the X‐ray fluorescence absorption of resin within sediment; and (ii) the sediment dilution effects by resin. An improved micro‐X‐ray fluorescence correction equation based on X‐ray fluorescence emission theory considers the instrument's sensitivity to each element, which provides a reasonable explanation of these two effects. The resin‐corrected X‐ray fluorescence intensity was then successfully converted to elemental concentrations using simple linear regression between the data from micro‐X‐ray fluorescence scanning spectroscopy and from the conventional analyzer. In particular, the calculated concentration of SiO2 over the depth of the core, reflecting diatom/biogenic silica concentration, was significantly changed by the calibrations, from a progressively decreasing trend to an increasing trend towards the top of the core. [ABSTRACT FROM AUTHOR]