Assessment of groundwater quality and identification of contaminant sources of Liujiang basin in Qinhuangdao, North China

Liujiang basin is located in a typical rural mountain area dominated by agriculture and mining industry in Qinhuangdao, Hebei Province of China. Groundwater plays significant role for socioeconomic development in the area. 78 well samples and 11 spring samples showed great variation of chemical compositions and groundwater quality class across the study basin. Groundwater hydrochemical type in Liujiang basin is mainly dominated by the typical Ca Mg–HCO₃SO₄or Ca Mg–SO₄HCO₃. The relative abundance of constituents is in the following order: Ca²⁺ > Mg²⁺ > Na⁺ > K⁺for cations and HCO₃⁻ > SO₄²⁻ > Cl⁻for anions. Spring water quality is all good for drinking and irrigation, whereas about 33.00 % of the well water samples were not suitable for drinking and the exceeding indices included NO₃, total hardness, total dissolved solids and SO₄, and seven well samples were not suitable for agriculture use. The control of sodium and salinity hazard is required for irrigation. Natural processes include weathering-dominated, mineral weathering and ion exchange controlling groundwater chemistry. Principal component analysis and Pearson correlation matrices were used to identify groundwater contaminant sources and can be categorized as follows: (1) natural minerals dissolution and mine water mixing (2) domestic sewage and septic tank contamination and (3) agricultural fertilizer contamination. This study suggested that both natural and anthropogenic processes contributed to chemical composition of groundwater in Liujiang basin, especially the NO₃concentration is more than the acceptable limits in groundwater used for drinking purposes, indicating that anthropogenic nitrogen pollution is currently serious.