School of Marine Science and Technology, Tokai University, 3-20-1 Orido, Shimizu-ku, Shizuoka, 424-8610, Japan.
Research Institute for Humanity and Nature, 457-4 Motoyama, Kamigamo, Kita-ku, Kyoto, 603-8047, Japan.
Environ Monit Assess. 2020 Jun 29;192(7):467. doi: 10.1007/s10661-020-08292-4.
To evaluate the seasonal water circulation of Tonle Sap Lake and its tributary rivers in Cambodia, the spatial distribution patterns of major and trace elements in surface water were investigated. Based on the similarity of the dissolved elemental concentrations, the water samples were mainly divided into the three groups: samples with relatively high percentages of Ca, Mo, and Sb (Subcluster B1); samples with high Si, Al, and Fe (B2); and samples with high Na, K, and Mg (B3). During the rainy season, the elemental composition of lake water (B1) appeared to be greatly influenced by the intrusion of water from the Mekong River (B1) through the Tonle Sap River (B1). During the dry season, the type of lake water shifted to B3, suggesting that the lake water stored during the rainy season was replaced by inflow from other tributaries and groundwater in its vicinity. Thus, the seasonal changes in the elemental composition of the lake water were largely controlled by surface water and groundwater circulation. The dissolved As concentration was higher in the lake water and during the dry season than that in the river water and during the rainy season, indicating the discharge of As from the lake's bottom sediment during the dry season. Although the redox cycling of Fe and Mn appeared to be less important due to the shallow water depth in the lake, there are potential risks of As poisoning induced by the formation of an anoxic water mass and increment in the concentration of phosphorus if eutrophication continues to progress.
为了评估柬埔寨洞里萨湖及其支流的季节性水循环，研究了地表水主要和微量元素的空间分布模式。基于溶解元素浓度的相似性，水样主要分为三组：Ca、Mo 和 Sb 含量较高的样品（B1 亚群）；Si、Al 和 Fe 含量较高的样品（B2）；以及 Na、K 和 Mg 含量较高的样品（B3）。雨季时，湖水的元素组成（B1）似乎受到湄公河（B1）通过洞里萨河（B1）入侵的强烈影响。旱季时，湖水类型转为 B3，表明雨季储存的湖水被附近其他支流和地下水所取代。因此，湖水元素组成的季节性变化主要受地表水和地下水循环的控制。溶解态 As 浓度在旱季的湖水和旱季的河水中均高于雨季的湖水和雨季的河水中，表明旱季湖水底部沉积物中 As 的释放。尽管由于湖泊水深较浅，Fe 和 Mn 的氧化还原循环似乎不太重要，但如果继续富营养化，缺氧水团的形成和磷浓度的增加可能会导致 As 中毒的风险。
