Heavy metal distribution and assessment in Qanat system water sourced from the mountains surrounding the copper mine

Qanat, an important historical phenomenon in water consumption in desert areas, can be susceptible to heavy metal contamination resulting from mining activities. In this study, water samples from eight Qanats originating from the highlands surrounding the Sarcheshmeh copper mine in Rafsanjan, Iran, were examined for the presence of heavy metals, including cadmium (Cd), aluminum (Al), lead (Pb), and molybdenum (Mo). The cloud point method was used to extract the water samples, which were then analyzed using graphite-furnace atomic absorption spectrometry (GF-AAS). During the dry season, the levels of Pb (0.630 µg L⁻¹) and Mo (0.780 µg L⁻¹) were higher compared to the wet season (Pb: 0.399 µg L⁻¹ and Mo: 0.740 µg L⁻¹). However, Cd and Al (0.173, 0.720 µg L⁻¹ in the dry season and 0.174, 0.810 µg L⁻¹ in the wet season, respectively) didn’t show a significant difference between the two seasons. The results of this study indicate that the concentrations of all five metals exceeded the drinking and agricultural standards set by the World Health Organization (WHO). All the heavy metals levels in the water samples were below the standards set by the Food and Agriculture Organization (FAO). The mean values of the heavy metal evaluation index (HEI) were 0.057 and 0.062, and for the heavy metal pollution index (HPI) were 117.57 and 120.00 during the dry and wet seasons, respectively. The contamination degree (CD) mean value for both seasons was -3.94. Despite the relatively low values of HEI and CD, the Qanat water was deemed unsuitable for drinking due to the HPI exceeding the critical limit. Therefore, regular monitoring is necessary.