[H-TT18] Development and applications of environmental traceability methods

[HTT18-04] Sulfur isotopic compositions of sulfate in rainwater in the Kyoto-Osaka-Kobe area

*Yoriko Yokoo¹, Masato Kanamaru¹, Naoto Ishikawa² (1.Faculty of Science and Engineering, Doshisha University, 2.Graduate School of Human and Environmental Studies, Kyoto University)

Keywords:sulfur isotope, rainwater, non sea salt sulfate

We determined the sulfur isotope compositions (δ³⁴S) of monthly wet precipitation to elucidate the seasonal and regional variation in the provenance of dissolved sulfate. We collected manthly rainwater samples at Kyoto city and Kyotanabe city in Kyoto, at Neyagawa city in Osaka and at Nishinomiya city in Hyogo from January 2007 to December 2008.
We calculated the non-sea-salt (nss) SO₄^2- and nss-δ³⁴S in monthly rainwater samples on a Na basis. The nss-δ³⁴S were slightly lower than the δ³⁴S in monthly rainwater, indicating the effect of sea-salt on atmospheric deposition are small in the Kyoto-Osaka-Kobe area.
The nssδ³⁴S of monthly rainwater samples showed seasonal variation. The monthly rainwater samples in summer had the lower nss-δ³⁴S, suggesting nssSO₄^2- in atmospheric deposition contained sulfur derived from oil in industrial activities. On the other hand, the nss-δ³⁴S and nss-SO₄^2- deposition in the monthly rainwater samples in winter and spring showed higher than those in summer. These results suggest that the addition of coal from the eastern Asia to nssSO₄^2- in atmospheric deposition were occurred in winter and spring.
Sulfur isotopic compositions of monthly rainwater samples varied depending on seasons and sites, indicating they are useful tracer to study on the provenance of sulfur in atmosphere of urban area.