黄河三角洲浅层地下水化学特征及形成作用

Hydrochemical Characteristics and Formation Mechanism of Shallow Groundwater in the Yellow River Delta

黄河三角洲高效生态经济区开发建设和黄河下游生态调度均需要了解当地地下水化学特征.在沉积环境分区和补-径-排系统分区的基础上,采用数理统计与地统计、Piper三线图和离子比例系数等方法,对黄河三角洲浅层地下水化学特征及成因进行了系统研究.结果表明,①主要水化学参数Na+、Mg2+、Ca2+、Cl-、SO24-、HCO3-和TDS的质量浓度分别介于0.1～25.0g.L-1、3.6～3 815.0 mg.L-1、5.6～3 377.0 mg.L-1、0.1～45.1 g.L-1、24.2～4 947.0 mg.L-1、62.6～850.0 mg.L-1和0.4～80.7 g.L-1之间,各离子质量浓度均值进一步表明区域内Cl-、Na+和TDS质量浓度很高,而HCO 3-、CO23-和K+质量浓度很低.②Cl-和TDS质量浓度沿地下水流向逐渐增大,二者均呈现显著的方向性空间变异和空间分布一致性,揭示了Cl-是浅层地下水水质的主控离子.③从补给区到排泄区,浅层地下水水化学类型由Na+-Mg2+-Ca2+-Cl--SO42-等复杂类型快速过渡到Na+-Mg2+-Ca2+-Cl-(或Mg2+-Na+-Ca2+-Cl-)及Na+-Mg2+-Cl-型,并在海岸滩涂区演化成Na+-Cl-这一简单类型的水.④混合、蒸发浓缩、溶滤、阳离子交替吸附作用及人类活动的影响是黄河三角洲地区浅层地下水化学成分形成的主要作用.该地区浅层地下水化学特征形成的关键驱动因素是黄河入海流路的变迁和海水入侵.

Understanding the chemical characteristics of groundwater in the Yellow River Delta is very important.It can provide a useful reference for the development and construction of the Yellow River Delta High-efficiency Ecological Economic Zone and ecological regulation in the lower Yellow River.Based on partitioning the sediment environment and the recharge-runoff-discharge system,we studied the hydrochemical features and causes of shallow groundwater in the Yellow River Delta by mathematical statistics and geostatistics,Piper diagram,ion ratios and so on.Following results are obtained： ①Major cations and anions such as Na＋,Mg2＋,Ca2＋,Cl-,SO2-4,HCO-3and TDS concentrations range from 0.1-25.0 g·L-1,3.6-3 815.0 mg·L-1,5.6-3 377.0 mg·L-1,0.1-45.1 g·L-1,24.2-4 947.0 mg·L-1,62.6-850.0 mg·L-1 and 0.4-80.7 g·L-1.Average ion concentrations further indicate that Cl-,Na＋and TDS concentrations are high while HCO-3,CO2-3 and K＋concentrations are very low in the study area.②The Cl-and TDS concentrations of shallow groundwater possess conspicuous directional spatial variability and gradually increase along the groundwater flow direction,showing that Cl-is the most critical ion of shallow groundwater.③From the recharge area to the discharge area,shallow groundwater changes from the Na＋-Mg2＋-Ca2＋-Cl——SO2-4 facies to the Na＋-Mg2＋-Ca2＋-Cl-,Mg2＋-Na＋-Ca2＋-Cl-and Na＋-Mg2＋-Cl-facies,finally evolves into Na＋-Cl-facies in the coast.④Ion ratios indicate that the following main hydrochemical processes are inferred to control the shallow groundwater chemical composition： mixing,evaporation concentrating,mineral dissolution,cation exchange and adsorption and human activities.These findings strongly suggest that changes of the Yellow River water course and seawater intrusion are key drivers to form the chemical characteristics of shallow groundwater in the region.