Sulfur and strontium isotope geochemistry of tributary rivers of Lake Biwa: implications for human impact on the decadal change of lake water quality

To study the deterioration of the water quality in Lake Biwa, Japan, over the last 40 years, we measured the concentrations and isotopic ratios of sulfur and strontium of water in 41 inflowing rivers and one discharging river. The concentrations of SO 4 and Sr of inflowing rivers at downstream sites...

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Bibliographic Details
Published in:	The Science of the total environment Vol. 345; no. 1; pp. 1 - 12
Main Authors:	Nakano, Takanori, Tayasu, Ichiro, Wada, Eitaro, Igeta, Akitake, Hyodo, Fujio, Miura, Yuuta
Format:	Journal Article
Language:	English
Published:	Shannon Elsevier B.V 01-06-2005 Elsevier Science
Subjects:	Applied sciences Continental surface waters Earth sciences Earth, ocean, space Engineering and environment geology. Geothermics Environmental Monitoring Exact sciences and technology Fresh Water - chemistry Geologic Sediments - chemistry Geological Phenomena Geology Human Activities Human activity Japan Lake Biwa Natural water pollution Pollution Pollution, environment geology Rivers - chemistry Sr isotope Strontium Isotopes - analysis Sulfur isotope Sulfur Isotopes - analysis Water Pollutants, Chemical - analysis Water quality Water Supply - standards Water treatment and pollution Asia Japan Japan, Honshu, Shiga Prefect., Biwa L Sr isotope Lake Biwa Human activity Sulfur isotope Water quality Isotopic analysis Strontium isotopes Geochemistry Urban area Concentration measurement Watershed Surface water Lakes Stream Water pollution Sulfur isotopes Population density Anthropogenic factor
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Summary:	To study the deterioration of the water quality in Lake Biwa, Japan, over the last 40 years, we measured the concentrations and isotopic ratios of sulfur and strontium of water in 41 inflowing rivers and one discharging river. The concentrations of SO 4 and Sr of inflowing rivers at downstream sites were generally high in the southern urban area and in the eastern area, where a large agricultural plain is situated, but low in the northern and western areas, whose watersheds are mountainous and with low population density. SO 4 and Sr concentrations are also lower at upstream sites, which are closer to mountainous areas. Thus, the inflowing river receives large amounts of SO 4 and Sr as it flows across the plain, where human activity levels are high. The δ 34S or 87Sr/ 86Sr values of most eastern rivers at downstream sites are lower than those of water in Lake Biwa, and values become more uniform as the proportion of the plain area in the watershed increases. River water in other areas has higher values of δ 34S or 87Sr/ 86Sr than the lake water. This result indicates that the decadal decrease of δ 34S and 87Sr/ 86Sr in the lake water has been caused mainly by the increased flux of SO 4 and Sr from rivers in the eastern plain. We assume that in the plain, sulfur, nitrogen, and organic compounds induced by human activities generate sulfuric, nitric, and organic acids in the water, which accelerate the extraction of Sr from bedrocks, leading to the generation of Sr in the river water in the area.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0048-9697 1879-1026
DOI:	10.1016/j.scitotenv.2004.10.014