Antarctic Study on Tropospheric Aerosol and Snow Chemistry (ASTASC) in JARE Phase X

The Tenth Symposium on Polar Science/Special session: [S] Future plan of Antarctic research: Towards phase X of the Japanese Antarctic Research Project (2022-2028) and beyond, Tue. 3 Dec. / Entrance Hall (1st floor) at National Institute of Polar Research (NIPR

Isotopic evidence for acidity-driven enhancement of sulfate formation after SO2 emission control

After the 1980s, atmospheric sulfate reduction is slower than the dramatic reductions in sulfur dioxide (SO2) emissions. However, a lack of observational evidence has hindered the identification of causal feedback mechanisms. Here, we report an increase in the oxygen isotopic composition of sulfate (Δ17OSO42-) in a Greenland ice core, implying an enhanced role of acidity-dependent in-cloud oxidation by ozone (up to 17 to 27 in sulfate production since the 1960s. A global chemical transport model reproduces the magnitude of the increase in observed Δ17OSO42- with a 10 to 15 to sulfate in Eastern North America and Western Europe. With an expected continued decrease in atmospheric acidity, this feedback will continue in the future and partially hinder air quality improvements

A simple and reliable method reducing sulfate to sulfide for multiple sulfur isotope analysis

International audienceRationale: Precise analysis of four sulfur isotopes of sulfate in geological and environmental samples provides the means to extract unique information in wide geological contexts. Reduction of sulfate to sulfide is the first step to access such information. The conventional reduction method suffers from a cumbersome distillation system, long reaction time and large volume of the reducing solution. We present a new and simple method enabling the process of multiple samples at one time with a much reduced volume of reducing solution. Methods: One mL of reducing solution made of HI and NaH 2 PO 2 was added to a septum glass tube with dry sulfate. The tube was heated at 124°C and the produced H 2 S was purged with inert gas (He or N 2) through gas-washing tubes and then collected by NaOH solution. The collected H 2 S was converted into Ag 2 S by adding AgNO 3 solution and the co-precipitated Ag 2 O was removed by adding a few drops of concentrated HNO 3. Results: Within 2-3 h, a 100% yield was observed for samples with 0.2-2.5 μmol Na 2 SO 4. The reduction rate was much slower for BaSO 4 and a complete reduction was not observed. International sulfur reference materials, NBS-127, SO-5 and SO-6, were processed with this method, and the measured against accepted δ 34 S values yielded a linear regression line which had a slope of 0.99 ± 0.01 and a R 2 value of 0.998. Conclusions: The new methodology is easy to handle and allows us to process multiple samples at a time. It has also demonstrated good reproducibility in terms of H 2 S yield and for further isotope analysis. It is thus a good alternative to the conventional manual method, especially when processing samples with limited amount of sulfate available.-This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited

Homogeneous sulfur isotope signature in East Antarctica and implication for sulfur source shifts through the last glacial-interglacial cycle

International audienceSulfate aerosol (So 4 2−) preserved in Antarctic ice cores is discussed in the light of interactions between marine biological activity and climate since it is mainly sourced from biogenic emissions from the surface ocean and scatters solar radiation during traveling in the atmosphere. However, there has been a paradox between the ice core record and the marine sediment record; the former shows constant nonsea-salt (nss-) So 4 2− flux throughout the glacial-interglacial changes, and the latter shows a decrease in biogenic productivity during glacial periods compared to interglacial periods. Here, by ensuring the homogeneity of sulfur isotopic compositions of atmospheric nss-So 4 2− (δ 34 S nss) over East Antarctica, we established the applicability of the signature as a robust tool for distinguishing marine biogenic and nonmarine biogenic So 4 2−. Our findings, in conjunction with existing records of nss-SO 4 2− flux and δ 34 S nss in Antarctic ice cores, provide an estimate of the relative importance of marine biogenic So 4 2− during the last glacial period to be 48 ± 10% of nss-SO 4 2− , slightly lower than 59 ± 11% during the interglacial periods. Thus, our results tend to reconcile the ice core and sediment records, with both suggesting the decrease in marine productivity around Southern ocean under the cold climate