Over twenty years trend of chloride ion concentration in Lake Biwa
Over twenty years trend of chloride ion concentration in Lake Biwa
复制标题
琵琶湖氯离子浓度二十年变化趋势
DOI：
10.4081/jlimnol.2003.s1.42
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发表时间：
2003
影响因子：
1.6
通讯作者：
K. Ishikawa
中科院分区：
文献类型：
--
作者：
Y. Aota;M. Kumagai;K. Ishikawa
考虑了近期琵琶湖氯离子浓度的增加。在过去20年中，在琵琶湖北盆地的数据表明，氯离子浓度一直在不断增加，从7.4到9.9毫克升-1-0.5米深的湖面和7.3到9.9毫克升-1以上的底部（深度超过80米的湖面）。然而，这一低水平的盐度表明，在20年中增加了约35%。本文报道了近20年来琵琶湖部分测点氯离子浓度的变化趋势和变化趋势，以及气候资料的变化。在一年的短时间内，上层水体中氯离子浓度波动明显。这种波动主要受降水的影响。在琵琶湖南部流域中，氯离子浓度也有类似的变化趋势，但浓度远高于北部流域。并对5条集水面积大、水位高、降水量大的主要河流氯离子浓度的长期变化进行了讨论。河流流量数据表明，与其他河流相比，在北部盆地南部的一些河流中含有相对较高的氯化物浓度。此外，我们提出了一个简单的概念模型与可变流出和流入通量。该概念模型表达了氯化物收支量。利用琵琶湖的氯离子浓度数据和湖水排放数据，估算了从分水岭流入琵琶湖的平均氯离子通量。模型分析结果与对琵琶湖贡献较大的12条主要河流的数据比较表明，河流入湖是导致该湖氯离子浓度升高的主要来源之一，非点源入湖也是重要来源。
Recent increase of chloride ion concentration in Lake Biwa was considered. Over the past 20 years' data at the North Basin of Lake Biwa showed that chloride ion concentration has been continuously increasing from 7.4 to 9.9 mg l-1 at 0.5 m depth from lake surface and from 7.3 to 9.9 mg l-1 above the bottom (depth of over 80 m from lake surface). This low level salinity indicated, however, about 35% increase through 20 years. In this paper, we reported the trend and the tendency of chloride ion concentration at some locations and the change of climatic data through 20 years in Lake Biwa. In a short period within one year, chloride ion concentration clearly fluctuated in the upper water layer. This fluctuation was mostly influenced by precipitation. Similar trend of chloride ion concentration could be seen in the South Basin of Lake Biwa with much higher concentration than that in the North Basin. We also discussed the long-term changes of chloride concentrations in 5 major rivers with large catchment area, water level and precipitation. The data of river discharge indicated that some rivers in the southern part of the North Basin in Lake Biwa contain a relatively high chloride concentration compared with others. Furthermore, we proposed a simple conceptual model with variable outflow and inflow fluxes. This conceptual model expressed an amount of chloride budget. We estimated the average chloride flux flowing from the watershed into Lake Biwa using the data of chloride ion concentration in the lake and the data of water discharge from the lake. Comparing the results of the model analysis with the data of 12 major rivers contributing large flux to Lake Biwa, we suggested that river inflow is one of the major sources to induce the increase of chloride ion concentration in the lake, and the inflow from non-point source can be also important sources.