Groundwater quality and the potentiality in health risk assessment in Zhengzhou, China
Groundwater quality and suitability for drinking purposes in Zhengzhou City were investigated. A total of 30 water samples from 15 major monitoring wells were collected in January (dry season) and July (wet season), 2009. Seven common physicochemical (pH, permanganate index, ammonia, chloride, sulfate, hardness and the total dissolved solids) and 11 toxicological parameters (fluorine, nitrate, Zn, Fe, Mn, Cu, Cd, Pb, Se, Cr (VI) and As) were analyzed. Human health risk assessment for pollutants and water quality index for drinking purposes were also evaluated. The results showed that 6.7% of groundwater samples were considered as permissible for drinking and others as desirable; concentrations of chromium (VI) at site 14 and 15 were lower than the risk-based concentration associated non-carcinogenic effects (0.11 mg l−1), while higher than the standard associated carcinogenic effects (4.5E-5 mg l−1). The carcinogenic risk was 3.75E-6 at site 14 and 4.55E-6 at site 15, which indicated that the risks at both sites were serious. The uncontrolled consumption of poor quality groundwater may be dangerous for local human health. Concentrations of other elements were not detected nor found to be exceeding the highest acceptable limit of World Health Organization. Water quality index indicated that the quality of all the groundwater samples collected was excellent during both dry and wet seasons. Lower water quality indices during the wet season indicated a better quality of the groundwater than the dry season, and the main reasons were external input following seasonal rainfall events and evaporation. Significant variation of water chemistry strongly expressed the impact of surface contamination sources, overexploitation and mineral dissolution.