基于多变量统计分析和水化学特征的海水入侵特征研究——以青岛市崂山区为例

沿海地区地下水环境问题日益突出，进行地下水水化学特征及演化规律的研究，能够更有效地开展地下水环境的监测和保护。以青岛市崂山区地下水为研究对象，综合运用统计分析、主成分分析、Piper图解法、HFE-D图解法、Chadha’s矩形图法等方法，对研究区海水入侵特征与地下水化学特征演化进行分析，探究地下水水化学特征及演化规律，并进一步评价了海水入侵现状。结果表明，研究区地下水以Na+、Ca2+、Cl−、${rm{SO}}_4^{2-}$为主要优势离子，地下水化学类型多为Cl·SO4-Na型和SO4·Cl-Ca·Mg型。地下水中Cl−浓度变化幅度较大，且其均值超出了有无海水入侵的分界值（250 mg·L−1），地下水可能发生一定程度的海水入侵；青岛市崂山区地下水呈中性至弱碱性（pH均值=7.0~8.0），是沿海地区长期的水文地球化学过程的影响；地下水化学变化主要受自然因素（岩石与水的相互作用）或人为因素（农业和家庭活动）的控制；采用反距离加权（IDW）方法，结合地理信息系统（GIS），进行海水入侵位置的空间映射，研究结果表明崂山区海水入侵主要分布于江家土寨东−浦里社区北入侵段，王哥庄−港西−港东入侵段、仰口湾入侵段、登瀛村−栲栳岛入侵段。

Characterization of seawater intrusion based on multivariate statistical analysis and water chemistry characteristics: A case study of Laoshan district,Qingdao City

Groundwater is an important source of freshwater in coastal areas. With the rapid development of industrialization and urbanization, the water demand for production and living in coastal areas has been rising year by year. Therefore, the increasing exploitation of groundwater has triggered seawater intrusion and increasingly prominent environmental problems of groundwater in many places. Researching the hydro-chemical characteristics and evolutionary patterns of groundwater enables effective monitoring and protection of the groundwater environment. Taking the groundwater in Laoshan district, Qingdao City as the research object, we mainly focused on the issues of groundwater chemical characteristics, groundwater chemical processes, the degree of seawater intrusion and its impact on groundwater. In addition, under the theoretical guidance of hydrogeology, we analyzed the characteristics of seawater intrusion and evolution of groundwater hydrochemistry in the study area by means of data collection, theoretical analysis, field investigation and sample collection and testing. The research findings can provide a scientific basis for the rational development and utilization of groundwater in the area.The results show that the groundwater in the study area has Na+, Ca2+, Cl−, and ${rm{SO}}_4^{2-}$ as the main dominant ions, and most of the groundwater chemistry types are Cl·SO4-Na and SO4·Cl-Ca·Mg types. The Cl− concentration in the groundwater varied considerably and its mean value exceeded the cut-off value for the presence or absence of seawater intrusion (250 mg·L−1), indicating that some degree of seawater intrusion may have occurred in groundwater. Groundwater in the Laoshan district of Qingdao City is neutral to weakly alkaline (mean pH=7.0–8.0), which is an effect of long-term hydrogeochemical processes in the coastal area. The results obtained by the PCA model show that changes in groundwater chemistry are mainly controlled by natural factors (rock-water interaction) or anthropogenic factors (agricultural and domestic activities). The five chemical characteristics of Cl−, mineralization, ${rm{SO}}_4^{2-}$, γCl−/γHCO$_3^- $ and SAR were selected as evaluation factors. Based on the inverse distance weighting (IDW) method and geographic information systems (GIS), we achieved the spatial mapping of seawater intrusion locations, showing that the seawater intrusion, in Laoshan district was mainly distributed in the intrusion sections such as the east of Jiangjia Tuzhai—the north of Puli community, the area of Wanggezhuang-Gangxi-Gangdong, Yangkou bay and the area of Danying village-Quanzhou island. The study results are of great significance for the use of groundwater resources and the prevention and control of seawater intrusion in Laoshan district. In addition, the research ideas and methods provide a reference for the study of groundwater genesis in other coastal areas in the world.