Heavy Metal(loid)s in the Groundwater of Shabestar Area (NW Iran): Source Identification and Health Risk Assessment

The aims of this study are to investigate the potential origin of selected heavy metal(loid)s in the Shabestar plain, NW Iran, by means of multivariate statistical techniques (cluster analysis and factor analysis), as well as to determine the dominant factors that affect groundwater quality and to assess the health risk induced by metal(loid)s using the hazard quotients (HQ). Totally, 29 groundwater samples were collected from wells in August 2016, and the values of 23 parameters, namely pH, electrical conductivity, concentration of major elements (Ca2+, Mg2+, Na+, K+, HCO3-, SO42-, Cl-), minor elements (NO3-, F-, B, and Br-) and heavy metal(loid)s (Fe, Al, Cr, Mn, As, Zn, Pb, Cu, and Ni) were measured. The results indicate that some samples were found with As, Pb, and Zn concentrations exceeding WHO standards for drinking water. Results of correlation coefficients between the measured variables reflect the occurrence of weathering and dissolution of rocks, especially silicates and evaporites, with ion exchange and geochemical characteristics similar to the release of some heavy metal(loid)s. According to hierarchical cluster analysis, samples of cluster 1 are affected by alkalinity and accompanied by elements compatible with alkaline ambience (CO32- and Ni). Samples of subcluster 2-1 demonstrate the effect of salinity, attributed to evaporates, irrigation return flow, and influx of Urmia Lake's brine, while, samples of sub-cluster 2-2 are influenced by agricultural activities. Factor analysis results illustrate the effects of five factors on the quality of groundwater. The factor analysis accounts for the 71.9% of total variance of groundwater quality for geogenic impacts, while 10% of the groundwater quality variance is controlled by agricultural activities which produce excessive amounts of NO3- along with Zn which is contained in fertilizers and agrochemicals. The results of the human health risk assessment show that As is the most dominant metalloid in inducing maximum noncarcinogenic risk among all the heavy metal(loid)s. Based on HI, 45 and 14% of the samples for children and adults, respectively, are found to be in high risk category.