Hydrogeochemical characteristic evaluation and irrigation suitability assessment of shallow groundwater in Dangshan County, China

Abstract

The current study aims to identify the hydrogeochemical characteristics, formation mechanism and evolution law of shallow groundwater in Dangshan, China, and to evaluate the suitability of the groundwater for irrigation. In this study, ninety-six samples were taken to investigate the hydrogeochemical characteristics of shallow groundwater in Dangshan County. The geographic information system (GIS) method was used to analyse the spatial distribution characteristics of total dissolved solids (TDS). Gibbs diagram, Binary relation analysis and reverse geochemical reaction simulation method were utilised to reveal the main formation mechanism of relatively high TDS in this region. The results show that water-rock interaction and evapotranspiration are the main mechanisms for controlling the chemical evolution of shallow groundwater in wet and dry seasons in the study area, respectively. The main waterrock interactions in the study area include dissolution of halite and dolomite, the precipitation of gypsum, as well as cation exchange and adsorption. Suitability of shallow groundwater quality for irrigation use was evaluated according to the sodium adsorption ratio (SAR) and the electrical conductivity (EC) with a United States Salinity Laboratory (USSL) diagram. Meanwhile, GIS technology was used to demonstrate the spatial distribution of irrigation suitability variations. Based on the spatial interpolation result on the USSL salinity diagram classification, the shallow groundwater in 89% of the study area is suitable for irrigation, while 11% of the area is unsuitable for irrigation.