中文摘要：

地下水一直是广东硇洲岛唯一的水资源，但近年来许多地区地下水咸化趋势加剧，严峻威胁着岛上居民的用水安全，研究地下水化学演化及成因机理，对预防和减缓水质变成意义重大。本文结合区域水文地质条件、地形地貌条件及水化学资料分析了整个岛屿地下水水质状况。在此基础上采用Piper三线图研究了水化学特征，并利用PHREEQC软件对水文地球化学演化规律进行模拟研究，结果表明：（1）海水入侵是造成地下水成化的主要原因，咸化对水质的影响主要表现为Cl-的增加，Ca2＋在区分该地区不同水体时反应灵敏，是良好的识别指标之一；（2）海水入侵的过程中，过渡带前缘不存在经受长期古海水演化而成的卤水与地下淡水的混合作用，地下水中Mg2＋、Ca2＋与Na＋之间存在着强烈的离子交换，石膏、白云石及方解石处于不饱和状态；（3）浅层地下水与深层地下水之间无明显的水力联系，属于相对独立的地下水流系统。在全球变暖，海平面上升的总趋势下，海岛地下水开发必须合理规划、严格管理，以防引发大规模海水入侵灾害的发生。

英文摘要：

Groundwater is the only resource in the Naozhou Island, Guangdong Province. Since the quality of the shallow fresh groundwater has been deteriorating a lot for increasing of TDS in recent years, it has been a burning issue to research hydrochemical evolution and formation mechanism of groundwater to prevent or reduce the deterioration. Based on hydrochemical characteristics and regional hydrogeological and topographic conditions, this paper discussed on the process of water chemical evolution and causes of groundwater salinization. PHREEQC software and piper diagram were applied respectively to simulate the groundwater spatial pattern and hydrochemical features. The results show that： （1） Groundwater salinization is controlled by seawater intrusion which contributes to the rapid increase of Cl-, Ca2＋ is able to distinguish different water effectively and proved to be a sensitive index; （2） There is no mix between fresh water and brine which evolved from ancient seawater in intermediate aquifer, Saturation indexes （SI） of gypsum, calcite and dolomite are out of equilibrium （undersaturated）, which contributes to ion exchange reactions among Mg2＋, Ca2＋ and Na~; （3） Shallow and deep aquifers have respective systems of groundwater circulation without hydraulic connection. Consequently, groundwater exploitation of island requires rational planning and stringent regulations to avoid severe seawater intrusion in the general trend of sea level rise.