An investigation into the hydrochemistry, quality and risk to human health of groundwater in the central region of Shandong Province, North China

Abstract This study aimed to characterize the hydrochemistry and risk to human health of groundwater in the central region of Shandong Province (CRSP) as well as to investigate the factors controlling groundwater quality. Methods applied included traditional hydrochemical analysis methods, the water quality index (WQI) and a health risk model. The results showed that groundwater of the CRSP is weakly alkaline, with average concentrations of total dissolved solids (TDS) over the wet and dry seasons of 666.2 mg·L−1 and 653.9 mg·L−1, respectively. The southeast part of the study region and Laiwu, Xintai and Taian showed higher concentrations of TDS and NO3−. The dominant hydrochemical types of groundwater in the CRSP were identified to be HCO3-Ca·Mg and SO4·Cl-Ca·Mg. The main factors influencing the hydrochemical composition of groundwater in CRSP were identified to include rock weathering, cation exchange and anthropogenic inputs, and the main source of nitrate in groundwater was identified as agricultural activities. The results of the water quality evaluation showed that most groundwater samples of the CRSP were suitable for drinking and agricultural irrigation. However, the non-carcinogenic risk index (HQ) values calculated for groundwater of the CRSP over both the dry and wet seasons indicated unacceptable risk to the health of both children and adults. The contradicting results between the water quality evaluation and health risk assessment were due to differences in the water quality standard limits used. It is suggested that permissible limits of water quality variables be adjusted according to local conditions and that a water quality evaluation system be established that is suitable for Chinese residents, so as to ensure the sustainable management of groundwater and the safety of drinking water.