张家口地区枯水期地下水水化学特征及其成因机制分析

Hydrochemical Characteristics and Genesis Mechanism of Groundwater in the Dry Period in the Zhangjiakou Area

为更好支撑首都水源涵养功能区和生态环境支撑区建设,开展张家口地区枯水期地下水水化学特征及其形成机制研究,对地下水资源合理开发利用具有重要参考意义.采集41组地下水样品,运用描述性统计分析、Piper三线图、相关性分析、Gibbs图及离子比值等方法,分析了研究区地下水水化学类型、组成特征和控制因素.结果表明,研究区地下水整体呈弱碱性,总硬度变化范围为105.00~1433.00 mg·L^(-1),ρ(TDS)变化范围在137.00~2286.00 mg·L^(-1),坝上地区地下水中总硬度和TDS质量浓度均高于坝下地区.研究区地下水中HCO_(3)^(-)和Na^(+)为主要优势阴、阳离子.地下水中主要组分超标率最高的为总硬度,超标率为36.59%,坝上地区地下水中各组分的超标率和最大超标倍数均大于坝下地区.研究区地下水水化学类型以HCO_(3)-Ca·Mg·Na型为主,坝上地区和坝下地区水化学类型差异较小,SO_(4)^(2-)、Cl^(-)、HCO_(3)^(-)、Na^(+)和Mg^(2+)对TDS的贡献最大.地下水水化学特征受盐岩、钠长石和白云岩等岩石矿物风化溶滤作用、阳离子交换作用和人类活动的共同影响,蒸发结晶和大气降水对研究区地下水主要离子来源贡献较小.坝上地区地下水受人类活动影响要大于坝下地区,其中NO_(3)^(-)主要来源于农业活动.

In order to better support the construction of the capital water conservation functional area and ecological environment support area,research on the chemical characteristics of groundwater and its formation mechanism in the dry period in the Zhangjiakou area can provide a great reference for the rational development and utilization of groundwater resources.A total of 41 groups of groundwater samples were collected,and the hydrochemical types,composition characteristics,and control factors of groundwater in the study area were analyzed by using the combined method of descriptive statistical analysis,Piper triplot,correlation analysis,Gibbs plot,and ion ratio.The results showed that the groundwater in the study area was weakly alkaline,with the total hardness and ρ(TDS)ranging from 105.00 mg·L^(-1) to 1433.00 mg·L^(-1) and 137.00 mg·L^(-1) to 2286.00 mg·L^(-1),respectively.The total hardness and TDS mass concentrations of groundwater in the Bashang area were higher than those in the Baxia area.HCO_(3)^(-) and Na^(+)were the main dominant anions and cations in the groundwater in the study area.The highest overstandard rate of the main components in groundwater was that of total hardness(36.59%).The overstandard rate and maximum excess multiple of each component in groundwater in the Bashang area were greater than those in the Baxia area.HCO_(3)-Ca·Mg·Na was the main type of groundwater hydrochemistry in the study area,and there was little difference between the Bashang area and the Baxia area.SO_(4)^(2-),Cl^(-),HCO_(3)^(-),Na^(+),and Mg^(2+)contributed the most to TDS.The chemical characteristics of groundwater were affected by weathering and filtration of rock minerals such as salt rock,albite,and dolomite;cation exchange;and human activities.Evaporative crystallization and atmospheric precipitation contributed to a small part of the main ion source of groundwater in the area.The effect of human activities on groundwater in the Bashang area was greater than that in the Baxia area,and NO_(3)^(-)mainly originated from agricultural activities.