Groundwater quality evaluation using the pollution index and potential non-carcinogenic risk related to nitrate contamination in the karst aquifers of Bokoya massif, northern Morocco

In recent years, the sharp increase in nitrate concentration in groundwater has become an important health issue worldwide, and uncontrolled groundwater use can cause potentially dangerous problems for human health. The aim of the present study is to determine the degree of groundwater pollution in the Bokoya massif, located in the Moroccan Rif, and to quantify the non-cancer risks associated with its consumption. Two rounds of sampling were carried out during April and September 2018, respectively collecting 96 and 73 samples distributed between wells and springs covering the entire study area. The pollution index results showed that 39% and 41% of the studied springs possess a pollution degree ranging from moderate to very high during the wet and dry periods, respectively. Deterioration of the water quality is mainly linked to strong mineralisation from mineral dissolution of Palaeozoic and Predorsal rocks, and to the high concentrations of anthropogenic nitrates found in the limestone formation. The assessment of non-carcinogenic risk by oral exposure to nitrates showed that about 47%, 45% and 43% of the samples constitute non-carcinogenic risk to the health of children, adult women, and adult men, respectively. Children have a slightly higher exposure to non-carcinogenic risks. In a situation typified by both the scarcity of drinking water and a lack of population-wide information for the study area, the results of this study will help guide decision-makers and water resource management services towards a policy of limiting the sources of nitrates found in aquifers in order to limit the potentially harmful effects on human health.