北海市铁山港东部地区地下水水化学特征及形成机制

Hydrochemical Characteristics and Formation Mechanism of Groundwater in the Eastern Region of Tieshangang District,Beihai City

地下水为北海地区经济社会发展提供有力的资源支撑,研究该地区地下水水化学特征及形成机制对区域地下水资源合理开采及可持续利用和服务海岸带生态安全建设具有重要意义。本研究在北海市铁山港东部地区开展了地下水调查、水样采集与分析,并综合运用描述性统计分析、Gibbs图以及离子比值等方法分析了地下水水化学特征及水岩相互作用机理。结果表明:研究区地下水具有矿化度和pH值低的显著特点,潜水水化学类型为Na·Ca-Cl·HCO_(3)·NO_(3)、Na·Ca-Cl·NO_(3)和Na·Ca-Cl型;承压水水化学类型以Na·Ca-Cl·HCO_(3)·NO_(3)、Na·Ca-Cl·NO_(3)和Na-Cl·NO_(3)型等为主,Na^(+)、Cl^(-)质量浓度沿径流方向增加明显。地下水的形成过程主要受到硅酸盐和蒸发盐矿物溶解、阳离子交换作用等的控制,且受到一定程度人类活动的影响。硝酸盐在地下水中普遍存在,有55.2%的承压水和66.7%的潜水样品表现为硝酸型水,指示区内地下水有受到污染的趋势。建议重视研究区地下水污染防治,尤其注意化肥的科学使用,并加强对工业、生活排污的有效处理。

Groundwater resources provide strong support for the economic and social development in the Beihai area.Therefore,the study of the hydrochemical characteristics and formation mechanism of groundwater in this area is important for the rational exploitation and sustainable utilization of regional groundwater resources,and of great significance in the construction of ecological security in the coastal zone.In this paper,groundwater investigation,water sample collection and analysis were carried out in the eastern region of Tieshangang District,Beihai City;the groundwater hydrochemical characteristics and water-rock interaction mechanism were analysed with descriptive statistical analysis,Gibbs diagram and ion ratio methods.The results show that the groundwater of the study area is characterized by a low degree of mineralization and pH value.For phreatic water,hydrochemical types are mainly Na·Ca-Cl·HCO_(3)·NO_(3),Na·Ca-Cl·NO_(3) and Na·Ca-Cl types.The Na·Ca-Cl·HCO_(3)·NO_(3),Na·Ca-Cl·NO_(3) and Na-Cl·NO_(3) types predominate in the confined water,and the concentrations of Na^(+)and Cl^(-)increased along the groundwater flow path.The groundwater formation process is mainly controlled by the dissolution of silicate and evaporite minerals,cation exchange and is influenced by human activities to some extent.Nitrate is widespread in the groundwater,with 55.2%of the confined water and 66.7%of the phreatic water samples exhibiting NO_(3) type,indicating a trend of groundwater contamination in the area.This study suggests that attention should be paid to the prevention and control of groundwater pollution in the study area,especially the scientific use of chemical fertilizers and the effective treatment of industrial and domestic discharges.