Japan Geoscience Union Meeting 2014

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Poster

Symbol A (Atmospheric, Ocean, and Environmental Sciences) » A-HW Hydrology & Water Environment

[A-HW25_2PO1] Isotope Hydrology 2014

Fri. May 2, 2014 4:15 PM - 5:30 PM Poster (3F)

Convener:*Yasuhara Masaya(Geological Survey of Japan, AIST), Kohei Kazahaya(Geological Survey of Japan, AIST), Shinji Ohsawa Shinji(Institute for Geothermal Sciences, Graduate School of Science, Kyoto University), Masaaki Takahashi(Geological Survey of Japan (GSJ), National Institute of Advanced Industrial Science and Technology (AIST)), YUICHI SUZUKI(Faculty of Geo-Environmental Sience,Rissho University), Futaba Kazama(Social Cystem Engineering, Division of Engineering, Interdiciplinary Graduate School of Medical and Engineering, University of Yamanashi), Kazuyoshi Asai(Geo Science Laboratory)

4:15 PM - 5:30 PM

[AHW25-P03] Exploring the sources of sulfur ion deposition and runoff in forest watersheds on the northern side of Lake Biwa

*Koyomi NAKAZAWA1, Seigo HORIE1, Osamu NAGAFUCHI1, Ken'ichi OSAKA1, Takuro NISHIMURA1 (1.The University of Shiga Pref.)

To clarify the sources of sulfur ions in precipitation and runoff from forest watersheds, bulk deposition and stream water samples were collected within the small Kutsuki and Surumi forest watersheds on the northern side of the Lake Biwa basin, central Japan. Samples were analyzed for major ions and δ34S. Continuous monitoring from 1990 to 2010 showed that the average SO42-concentration in stream water samples was 1.62 ±0.31 (0.76, 3.58) mg l-1at Kutsuki and 6.59 ±1.54 (3.68, 16.1) mg l-1at Surumi (t-test, p<0.01). However, the average SO42-concentration in bulk deposition samples was similar in both watersheds: 2.15 ± 1.31 (SD) mg l-1(range, 0.202-10.2 mg l-1) at Kutsuki and 2.24 ± 1.29 mg l-1(0.350?6.07 mg l-1at Surumi (t-test, p>0.05). The δ34S values in bulk deposition samples fluctuated from +8.86 to +9.14‰ at Kutsuki and from +9.87 to +11.1‰ at Surumi, whereas non-sea salt (nss-) δ34S in stream water samples varied from +6.89 to +12.0‰ and from ?4.64 to +5.11‰ , respectively (t-test, p<0.01). It is said that the δ34S values in coal products from northern China varied from -3 to -1 ‰ and Japanese oil varied from +5 to + 18‰ .Our findings suggest that the difference in the ability of canopies in the watersheds to catch SO42-dry deposition is the reason for the significant difference in nss- δ34S values in stream water samples. The more open canopy in the Kutsuki watershed consists of young conifers and deciduous broadleaf trees, whereas the canopy in the Surumi watershed consists of mature conifer trees at a high density. Therefore, it appears that the Kutsuki watershed was only affected by SO42-deposition from the Asian continent.There were not any domestic air pollution sources on the north side of Kutsuki. In contrast, the dense canopy of the Surumi watershed was affected by local SO42-pollution sources of national roads which were located 1 km northwest from Kutsuki, rather than continental sources. Overall, this investigation suggests that the difference in stream water SO42-concentrations in both watersheds is caused by the canopy differences.