Integration of Heavy Metal Pollution Indices and Health Risk Assessment of Groundwater in Semi-arid Coastal Aquifers, South Africa

Abstract

The heavy metal contaminated groundwater results in serious health issues and hence this study attempts to address its sources of contamination using integrated techniques including indexed and statistical methods and its related health hazards. Groundwater pH varied from 5.3 to 8.3 indicating acidic to alkaline in nature. The heavy metal pollution index shows that the groundwater samples vary from low to high pollution class and 21% of the samples exceed the critical limit of 100 implying that they are highly polluted with respect to heavy metals and are unfit for human consumption. The heavy metal evaluation index reveals that all the groundwater samples fall under low pollution. The synthetic pollution index reveals that 2%, 74% and 24% of the samples are suitable, slightly and moderately polluted, respectively, with heavy metals. The water quality index reveals that 19% and 2% of the groundwater samples belong to the poor and very poor water quality category and are spatially situated on the central, northern and southern parts of the study region. Correlation matrix and principal component analysis revealed that weathering of aquifer matrix and anthropogenic activities are accountable for the release of heavy metals into groundwater. Furthermore, R-mode and Q-mode cluster analysis revealed two clusters that are linked to mixed sources including weathering and anthropogenic activities. Based on the hazard quotient, the order of heavy metal impact is Co>Pb>Cd>Zn>As>Mn>Cu>Cr>Fe>Ni for both children and adults. The hazard index values varied from 0.06 to 8.16 for children and from 0.02 to 2.14 for adults. In this study, it is discovered that 43% and 26% of groundwater samples pose a non-carcinogenic health risk in children and adults, respectively. This study highly recommends treatment of contaminated groundwater before consumption in order to protect and maintain public health. The results from this study can be useful for the local municipalities and the policy makers while considering management and mitigation plan to maintain the water quality and to control its adverse effect on human health.