Groundwater sources and the influencing factors on water quality in the river-lake transition zone of Lake Shengjin, lower reaches of the Yangtze River<sup>*</sup>

Abstract

为探究河湖过渡带地下水来源及其水质影响因素，本文分析了不同水体氢氧同位素的分布特征，确定地下水的补给来源，而后采用贝叶斯混合模型（MixSIAR）定量解析不同补给源对地下水的贡献率，并计算混合水源对地下水酸碱度（pH）、电导率（Cond）和总溶解固体（TDS）的贡献量，探究水源混合对地下水水质的影响.研究发现：近长江和湖岸的地下水同位素特征与长江水、湖水接近，其水力联系密切，而中部地下水同位素特征与河水接近，受河水补给明显；河水对地下水的贡献率最大，约为47%，降水贡献率约为20%，湖水和长江水的贡献率分别约为16%和17%；混合水源对pH的贡献率接近100%，对Cond的贡献率约为70%，而对TDS的贡献率很小.此外，生活污水、农业污染等外源输入也会导致地下水pH下降，Cond和TDS明显升高.;The distribution characteristics of δ¹⁸O and δD in precipitation, surface water and groundwater are analyzed, and the potential recharge sources of groundwater are determined. Then the MixSIAR model is used to calculate the contribution rate of different recharge sources to groundwater quantitatively, and the influence of water source mixing on groundwater's quality is also analyzed. The results show that the characteristics of δ¹⁸O, δD in groundwater near the Yangtze River and the lake are similar to those in the Yangtze River and lake, indicating that a close hydraulic connection exists. While δ¹⁸O, δD values in groundwater located in the middle region are similar to those in rivers, indicating that groundwater is mainly recharged by rivers. The contribute ratio of the river to groundwater is the largest, about 47%, that of precipitation is about 20%, lake and the Yangtze River are about 16% and 17%, respectively. The contribution rate of the mixed water source to the pH of the groundwater is close to 100%. And the contribution rate of the mixed water source to conductivity is about 70%, contributes the conductivity value in most of the groundwater samples, but only contributes a small part of the total dissolved solids value.