Sulfur and strontium isotope geochemistry of tributary rivers of Lake Biwa: implications for human impact on the decadal change of lake water quality
Sulfur and strontium isotope geochemistry of tributary rivers of Lake Biwa: implications for human impact on the decadal change of lake water quality
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DOI：
10.1016/j.scitotenv.2004.10.014
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发表时间：
2005-06-01
影响因子：
9.8
通讯作者：
Miura, Y
中科院分区：
文献类型：
--
作者：
Nakanao, T;Tayasu, I;Miura, Y
为了研究日本琵琶湖近40年来水质的恶化，我们测量了41条入湖河流和1条出湖河流的硫和锶的浓度和同位素比值。下游入流河流SO4和锶浓度在南部城区和东部地区普遍较高，而在北部和西部地区较低，这些地区的流域多山，人口密度低。上游地区的SO4和锶浓度也较低，因为这些地区靠近山区。因此，流入的河流在流经人类活动水平较高的平原时，会接收大量的SO4和锶。下游大部分东部河流的S-34或sr-87/sr-86值均低于琵琶湖水的值，且随流域平原面积比例的增加而趋于一致。其他地区河水的S-34或锶-87/锶-86值高于湖水。这一结果表明，湖水中S-34和锶-87/锶-86比值的年代际下降主要是由于东部平原河流中SO_4和锶的通量增加所致。我们推测，在平原地区，人类活动产生的硫、氮和有机化合物在水中生成硫酸、硝酸和有机酸，加速了基岩中锶的提取，导致了该区河水中锶的生成。(C)2004爱思唯尔B.V.保留所有权利。
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 SO4 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. SO4 and Sr concentrations are also lower at upstream sites, which are closer to mountainous areas. Thus, the inflowing river receives large amounts of SO4 and Sr as it flows across the plain, where human activity levels are high. The delta S-34 or Sr-87/Sr-86 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 delta S-34 or Sr-87/Sr-86 than the lake water. This result indicates that the decadal decrease of delta S-34 and Sr-87/Sr-86 in the lake water has been caused mainly by the increased flux of SO4 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. (c) 2004 Elsevier B.V. All rights reserved.