湛江市深层承压水铁分布和地球化学模拟研究

Study on Fe Occurrence and Geochemical Simulation of Groundwater in the Deep Confined Water in Zhanjiang

在广东省湛江市深层承压水开采过程中,在开采区内形成了区域水位降落漏斗。降落漏斗的形成对深层承压水的化学特性产生了一些影响,具体表现为:西部和西北部铁含量低,北部铁含量高,降落漏斗附近铁含量中等。对降落漏斗内深层承压水铁分布进行演化模拟计算,结果表明,降落漏斗内深层承压水的补给可能来自北部高铁承压水、西部和西北部低铁承压水以及浅层承压水。深层承压水由这些地下水混合而成,高铁地下水是主要补给来源。降落漏斗中心区深层承压水的大量人工开采导致其铁含量升高。地下水在向降落漏斗中心区的径流过程中,不但发生了方解石、白云石和赤铁矿的溶解作用以及菱铁矿和水绿矾的沉淀作用,而且发生了Na+与Ca2+的交换、铁氧化-还原反应等一系列复杂的水-岩作用。

A regional depression cone exists in groundwater level in the deep confined water owing to a longterm exploitation of groundwater in Zhanjiang, Guangdong. The formation of the depression cone has a certain effect on the chemical nature of groundwater in the deep confined water, resulting in low concentration of Fe in the western and northwestern parts, high concentrations of Fe in the northern part and medium concentrations of Fe near the center of the depression cone. Geochemical simulation was carried out for the Fe occurrence in groundwater in the depression cone. The results show that groundwater in the depression cone in the deep confined water may be supplied from groundwater in the north, northwest and west, or from groundwater in the shallow confined aquifers. Groundwater in the deep confined water is a mixture of the supplied groundwater, and the high Fe groundwater is a main source. Groundwater exploitation of large quantity in the deep confined water causes an increase in Fe contents in the groundwater. In the course of groundwater towards the center of the depression cone, not only the dissolution of calcite, dolomite and hematite, the precipitation of siderite and melanterite may occur, but also the cation exchange between Na ^＋ and Ca^2＋, Fe oxidation-reduction of Fe may occur.