Spatial distribution of health risk assessment of a drinking water reservoir exposed to urban agglomeration and industrial lead contamination in Istanbul, Türkiye

The Ömerli Dam, supplied by multiple rivers that provide a major amount of Istanbul's water demands for drinking and irrigation, is experiencing toxicological threats due to rapid expansion, increased industrial activity, and population growth in light of the impending global drought. In this study, multivariate statistical analysis and spatial distribution based on geographic information system (GIS) was used to examine the status of pollution and health risk, irrigation water quality, and stochastic geo-environmental risk sources of 16 potentially toxic elements (PTEs: Na, Mg, K, Ca, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, and Pb) concentrations from samples in the dam. Also, spatial analyzing of quality indices was used to assess the dam's feasibility for irrigation and drinking. As per the results of the study, the dam water has mild heavy metal (loid) pollution, which is measured at 16 PTE by the heavy metal (loid) pollution index (HPI) and heavy metal (loid) evaluation index (HEI) values. The pollution level is low during the rainy season and moderate during the dry season. The water at sampling station S3 (HPI = 146.50) is unfit for consumption and cannot be used for drinking. The majority of harmful metal species exhibited elevated concentrations (notably Pb: 51.78 μg/L, Cr: 8.55 μg/L) in the dam lake water, particularly during the dry season. The toxic metals Pb and Cd account for 15.95% of the total variance, with a high degree of loading. Lead concentrations were found to be above WHO and USEPA limit values only in S2 and S4 during the wet season, but above 0.01 mg/L in all stations except S1 during the dry. Dam water is acceptable for agricultural use, according on the results of the, sodium absorption rate, the percentage of Na and the magnesium damage index, average SAR < 0.9, Na% < 25, and MH < 50, respectively. HQ_ingestion and HI values (all less than 1 in all PTEs) indicate that noncarcinogenic impacts might occur. PRACTITIONER POINTS: Ömerli Dam provides most of the drinking and potable water needs of a mega city like Istanbul. With this study, toxic metal pollution of dam surface water and its possible effects on human health were analyzed for the first time on a spatially wide scale.