Effect of agriculture on water quality of Lake Biwa tributaries, Japan
Effect of agriculture on water quality of Lake Biwa tributaries, Japan
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DOI：
10.1016/j.scitotenv.2007.08.042
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发表时间：
2008-01-15
影响因子：
9.8
通讯作者：
Yachi, Shigeo
中科院分区：
文献类型：
--
作者：
Nakano, Takanori;Tayasu, Ichiro;Yachi, Shigeo
我们调查了自然环境和人类活动对日本中部的琵琶湖的影响。测定了该湖主要支流中19种元素的含量和S、Sr稳定同位素组成，并与循环期湖水中的相应值进行了比较。主成分分析结果表明，各支流下游溶解组分可分为第1组（HCO 3、SO 4、NO3、Ca、Mg、Sr）和第2组（Cl、Br、Na、K、Ba、Rb、Cs）。第1组成分的浓度高，在河流的南部地区，这是城市化和人口稠密，东部地区，其中包括平原，农业占主导地位，相比之下，河流的北方和西部地区，这主要是山区和人口稀少。工业区河水中第2组成分浓度较高。在河水中的SO 4的三角洲S-34值收敛到0 +/- 2千分之一的SO 4浓度的增加，不包括石灰石广泛分布的地区，作为HCO 3浓度的增加。特别是，在广泛种植水稻的东部平原地区的中小河流中，δ S-34值（0 +/- 2千分之一）和Sr-87/Sr-86比值（0.7117 +/- 0.0005）均处于狭窄范围内。这些值分别与日本琵琶湖流域肥料的S-34值和东部平原土壤交换性Sr-87/Sr-86值相一致。东部地区中小河流水质特征可以用化肥和水稻分解产生的硫酸、硝酸和重碳酸选择性浸出吸附在平原土壤和沉积物上的碱土元素或溶解的富含Mg和Sr的碳酸钙的模式来解释。由于反硝化作用，湖水中的NO3被耗尽，由于在底部沉积物的氧化还原条件下发生的矿化作用，湖水中的Mn被耗尽。除NO3和Mn外，通过简单的支流水混合，可以近似地再现出琵琶湖水体中溶解态元素和Sr、S同位素组成，表明这些组分为评价湖水与支流沃茨之间的关系提供了有效的指标。(C)2007 Elsevier B. V.保留所有权利。
We investigated the effects of natural environments and human activity on Lake Biwa, central Japan. We determined the concentrations of 19 elements and the compositions of stable S and Sr isotopes in the main tributaries of the lake and compared them with the corresponding values obtained from the lake water during the circulation period. Results of a principal component analysis indicated that the components dissolved in the lower reaches of the tributaries can be divided into group 1 (HCO3, SO4, NO3, Ca, Mg, Sr) and group 2 components (Cl, Br, Na, K, Ba, Rb, Cs). The concentrations of group 1 components were high in the rivers of the southern area, which is urbanized and densely populated, and the eastern area, which consists of plains where agriculture predominates, compared with the rivers of the northern and western areas, which are mostly mountainous and sparsely populated. The concentrations of group 2 components tended to be high in the river water of industrial areas. The delta S-34 values of SO4 in the river water converged to 0 +/- 2 parts per thousand as the SO4 concentration increased and, excluding the areas where limestone is extensively distributed, as the HCO3 concentration increased. In particular, both the delta S-34 values (0 +/- 2 parts per thousand) and the Sr-87/Sr-86 ratios (0.7117 +/- 0.0005) fell within narrow ranges in the small and medium rivers of the eastern plain area, where rice is widely grown. These values agreed respectively with the delta S-34 values of the fertilizers used in the Lake Biwa basin and the soil-exchangeable Sr-87/Sr-86 in the eastern plain. The characteristics of water quality in the small and medium rivers of the eastern area can be explained by a model in which sulfuric, nitric, and bicarbonic acids generated by the decomposition of agricultural fertilizer and paddy rice selectively leached out alkaline-earth elements adsorbed on the soil and sediments of the plain or dissolved calcium carbonate enriched with Mg and Sr. Compared with tributary waters, the lake water was depleted in NO3, owing to denitrification, and in Mn, owing to mineralization, which occur under the redox condition of bottom sediments. Excluding NO3 and Mn, the compositions of both the dissolved elements and the Sr and S isotopes in the water of Lake Biwa can be approximately reproduced by simple mixing of the tributary water, indicating that these components provide effective indices for evaluating the relationship between the waters of the lake and its tributaries. (C) 2007 Elsevier B.V. All rights reserved.