Groundwater quality evaluation in Huachuan-Jixian-Youyi area based on principal component analysis

Huachuan-Jixian-Youyi area in Sanjiang Plain is a key grain-producing area in Heilongjiang Province, and its water resources are directly related to agricultural production and ecological security. The demand for water resources continues to increase with the rapid development of industry and agriculture, leading to a series of problems such as declining groundwater levels and deteriorating water quality. The clarification of chemical characteristics, and the influencing factors of water quality, is of great significance to maintaining agricultural stability and sustainable development. Through collecting 15 groundwater samples in the field, the authors analgzed the groundwater chemical characteristics and causes by combining statistical analysis, piper trilinear diagram, hierarchical cluster analysis, principal component analysis, chlor-alkali index, etc., and evaluate the groundwater quality. Sodium adsorption ratio (S_AR), soluble sodium percentage (Na%), and residual sodium carbonate (R_SC) all showed good suitability for groundwater irrigation in the area. The main hydrochemical type was Ca²⁺-HCO₃^- type and locally Ca²⁺-Cl^- type. The chemical composition of groundwater was mainly controlled by rock weathering, with the main ions derived from the dissolution of rock salt and soluble carbonates such as calcite and dolomite. And the chlor-alkali index indicated that cation exchange also affected the formation of groundwater chemical components. The results of the water quality evaluation showed that the groundwater quality in Huachuan County and Jixian County was poor, and the NO₃^- concentration exceeded the standard seriously. The overstandard was not only affected by natural factors, but also related to the use of chemical fertilizers and pesticides, mining and other human activities. The study results could provide references for the rational development and management of groundwater resources.