珠海市酸性地下水分布特征及成因机制

Characteristics of Distribution and Genetic Mechanism of Acidic Groundwater in Zhuhai City

酸性地下水是我国南方广泛存在的水环境问题,查明酸性地下水的分布特征和成因机制,对区域地下水开发利用和水资源保护具有重要的科学意义。本文系统采集了珠海市不同类型的地下水样品211件,采用数理统计和水文地球化学等方法,分析并研究了地下水pH值的空间分布、酸性地下水的主要成因和影响因素。结果表明,研究区地下水pH值为3.24~8.23,大多数为6.06~6.52,以酸性水为主。地下水p H值随着地势降低而升高,大部分丘陵、台地区裂隙水的碱度和酸中和能力较弱,地下水酸性较强,平原区孔隙承压水的碱度和酸中和能力相对较强,地下水呈中性;地下水的酸碱度与大气降水、包气带介质、水岩相互作用以及河流、潮汐作用有关;酸雨的补给、偏酸性的包气带介质、花岗岩和陆源碎屑岩中的硅酸盐矿物化学风化和硫化物矿物的氧化水解是丘陵区地下水偏酸性的主要原因。

Acidic groundwater is a widespread water environment problem in southern China.The research on distribution characteristics and genetic mechanism of acidic groundwater has great scientific significance for the development and utilization of regional groundwater and the protection of water resources.211 groundwater samples in different aquifers in Zhuhai city were systematically collected,and the distribution and main genetic and influential factors of acidic groundwater were analyzed by the method of mathematical statistics and hydrogeochemistry.The results show that the groundwater is mainly acidic,with the pH from 3.24 to 8.23,and mostly between 6.06 and 6.52.The pH of groundwater increases with the decrease of the terrain.The alkalinity and acid neutralization ability of groundwater in most hilly platform areas are weak,and the acidity of groundwater is strong.The alkalinity and acid neutralization ability of pore phreatic water and pore confined water are relatively strong,and the groundwater is neutral.The acidity and alkalinity of groundwater in the study area are related to atmospheric precipitation,vadose zone medium,water-rock interaction,river and tidal action.The recharge of acid rain,acidic vadose zone medium,weathering and dissolution of silicate minerals in granite and terrigenous clastic rocks and the oxidative hydrolysis of sulfide minerals are the main genesis for the acidic groundwater.