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Rationale: Measurements of the multiple sulfur isotopic composition (δ34S, δ33S and δ36S values) of ancient sedimentary sulfide are useful for clarifying and reconstructing the picture of the global sulfur cycle on the early Earth. The methods used for these measurements should provide a high level of precision for the determination of sulfur isotope mass‐independent anomalies (∆33S and ∆36S values). Here we propose some improvements to the earlier published femtosecond laser‐ablation fluorination method to make it suitable for measuring both ∆33S and ∆36S values in the Archean sedimentary sulfides with acceptable precision. Methods: A new gas purification system for the laser‐ablation fluorination method has been developed. The design of this system is based on temperature‐controlled flow traps for cryogenic separation of SF6 gas from other fluorinated products produced by fluorination of sulfide minerals. Compared with the previous version of the purification system, the efficiency of SF6 purification was significantly improved, which in turn improved the precision of the method for in situ GC/IRMS measurements of 36S/32S ratios (and determination of ∆36S values). Results: The improved method was tested using IAEA reference materials, as well as samples of natural pyrite with zero and non‐zero sulfur isotope anomalies. For samples of ~12–13 nmol SF6 (optimal size), the overall precision of the method is ±0.03‰ for ∆33S values and ±0.27‰ for ∆36S values. This level of precision is satisfactory to examine the sulfur isotope anomalies in the rock. Conclusions: The improved femtosecond laser‐ablation fluorination method is applicable for in situ measurements of δ34S, ∆33S and ∆36S values in sulfide minerals. [ABSTRACT FROM AUTHOR]

Deciduous forest covers vast areas of permafrost under severe dry climate in eastern Siberia. Understanding the water cycle in this forest ecosystem is quite important for climate projection. In this study, diurnal variations in isotopic compositions of atmospheric water vapour were observed in eastern Siberia with isotope analyses of precipitation, sap water of larch trees, soil water, and water in surface organic layer during the late summer periods of 2006, 2007, and 2008. In these years, the soil moisture content was considerably high due to unusually large amounts of summer rainfall and winter snowfall. The observed sap water δ18O ranged from −17.9‰ to −13.3‰, which was close to that of summer precipitation and soil water in the shallow layer, and represents that of transpired water vapour. On sunny days, as the air temperature and mixing ratio rose from predawn to morning, the atmospheric water vapour δ18O increased by 1‰ to 5‰ and then decreased by about 2‰ from morning to afternoon with the mixing ratio. On cloudy days, by contrast, the afternoon decrease in δ18O and the mixing ratio was not observed. These results show that water vapour that transpired from plants, with higher δ18O than the atmospheric water vapour, contributes to the increase in δ18O in the morning, whereas water vapour in the free atmosphere, with lower δ18O, contributes to the decrease in the afternoon on sunny days. The observed results reveal the significance of transpired water vapour, with relatively high δ18O, in the water cycle on a short diurnal time scale and confirm the importance of the recycling of precipitation through transpiration in continental forest environments such as the eastern Siberian taiga. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]