Characteristics and driving mechanisms of evolution of groundwater chemistry in Huang-Huai-Hai Plain and its exploitation and utilization suggestions

This paper is the result of hydrogeological survy engineering.

Objective Groundwater is one of the major water resources to supply water for the production and daily life of human activities in the Huang-Huai-Hai Plain (HP). The deterioration of groundwater environment has become an important factor restricting social and economic development and ecological balance at the conditions of human activities. Understanding the characteristics and driving mechanisms of evolution of groundwater chemistry can provide an important reference for the rational development and utilization of groundwater resources.

Methods In this paper, the HP is divided into three hydrogeological units including piedmont plain, central plain, and coastal plain. The characteristics and driving mechanisms of evolution of groundwater chemistry in HP in China are studied by using Piper diagram, Gibbs diagram, and principal component analysis.

Results Results showed that TDS concentrations in groundwater increased gradually from piedmont plain to coastal plain, and groundwater was evolved from freshwater to brine via brackish water and salt water. Groundwater in the study area was from 44 hydrochemical facies in the piedmont plain increased to 74 hydrochemical facies in the central plain, and then decreased to 22 hydrochemical facies in the coastal plain. Among them, the hydrochemical facies of groundwater in the piedmont plain were dominated by CO₃-Ca · Mg and CO₃-Ca, and was mainly controlled by a 4-factors model, by contrast, groundwater chemistry in the central and coastal plains was controlled by two 3-factors models, respectively.

Conclusions The chemical characteristics of groundwater in the HP are obviously zonal, and the hydrochemical facies of groundwater from the piedmont plain to the coastal plain was evolved gradually from CO₃ facies to CO₃ · SO₄ facies, CO₃ · Cl facies, SO₄ facies, as well as SO₄ · Cl facies, and finally convert to Cl facies. The groundwater chemistry in the study area is mainly controlled by a variety of natural factors such as rock weathering, evaporative concentration, cation alternate adsorption, and seawater intrusion on the spatial aspect, and is obviously affected by various human activities (e.g., groundwater overexploitation, land use change, domestic sewage, fertilizers, and animal manure) on the time aspect. According to the different chemical characteristics of groundwater and the impact of human activities in the areas from piedmont plain to coastal plain, the management and control suggestions on the development and utilization of groundwater resources in the HP are put forward.