Assessment of the water quality of groundwater in Bohai Rim and the controlling factors—a case study of northern Shandong Peninsula, north China

This study collected 184 groundwater (GW) samples from 92 wells during the dry and wet seasons, respectively to understand the hydrochemical characteristics, water quality, and risk of GW nitrate (NO3−) to human health in northern Shandong Peninsula (NSP), China. The results showed that GW in the NSP is weakly alkaline and classified as hard fresh water. The mean concentration of NO3− in GW exceeded 100 mg·L−1, total hardness exceeded 450 mg·L−1, and total dissolved solids (TDS) was less than 1000 mg·L−1. A Piper diagram showed that the water chemistry of GW in the NSP was mainly of the SO4·Cl-Ca·Mg type. A Gibbs diagram and ion ratio analysis indicated that the weathering of silicate rocks and agricultural production were the dominant factors affecting the hydrochemical characteristics of GW in the NSP, with cation exchange, dissolution of salt rock, and weathering of carbonate rock also making contributions. Na+ and Cl− in GW are significantly affected by seawater aerosols in coastal areas. During the wet season, the hydrodynamic conditions of the aquifer are improved, agricultural activities are strengthened, and GW becomes generally homogenized. The water quality index classified the GW quality of the NSP as mainly of medium quality. There was a relatively consistent spatial distribution of water quality during different periods. Water samples of poor water quality were mainly distributed in the lower reaches of the Huangshui River. In addition, total hardness and NO3− concentrations were the main variables affecting the quality of GW in the NSP. The assessment of the risk NO3− in GW in the NSP to human health through the ingestion of drinking water demonstrated a significant risk (infants > children > adults). These results indicate the need for local management measures to reduce the potential health risks of GW quality in the NSP.