Groundwater quality evaluation using water quality index (WQI) and human health risk (HHR) assessment in Herat aquifer, west Afghanistan

Numerous political and economic crises, and successive wars in Afghanistan have put safe water resources at risk due to mismanagement in the country. In this study, groundwater quality in the Herat aquifer, western Afghanistan is evaluated by geochemical methods and quality indices. Total of 27 samples were collected and analyzed for nitrate, fluoride and trace elements. Sodium and bicarbonate are the main cation and anion, respectively. Various diagrams revealed that rock weathering and normal ion exchange may controls the major ion chemistry. Granitic or biotite gneiss rocks and leachate from the Herat urban sewage are the main sources of fluoride and nitrate, respectively. Geogenic source of the studied parameters was verified by principal component analysis (PCA). Groundwater is contaminated by F, As and U in the Northwest of the region, and by nitrate almost in the majority of samples, especially in urban areas. Water quality index (WQI) showed poor quality for 29.6% of the samples, and the best quality was observed in Southwest of the area. Also, based on heavy metal evaluation index (HEI), the highest pollution was observed in Northwestern region. Nitrate poses a serious health risk to consumers (particularly in central parts), so that non-carcinogenic risk (HQ) values ranged from 1.1 to 3 in most of the samples, and very high (> 3) non-carcinogenic risk values were observed in 4 sampling sites.