چکیده: (45 مشاهده)
Background: This study investigated the continuum of surface water contamination and treatment by quantitatively assessing human health risks and identifying sources of heavy metal pollution (Pb, Cd, Cu, and Zn) in the Ziarat River and the Naharkhoran Drinking Water Treatment Plant.
Methods: In this analytical study, 61 water samples were collected along the river course and from the inlet and outlet of the treatment plant. Heavy metal concentrations were determined using a 797 Metrohm polarograph. Human health risks for children and adults were evaluated using chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI), and lifetime cancer risk (LCR). Multivariate statistical techniques, including correlation analysis and source apportionment, were applied to identify potential pollution sources.
Results: Heavy metal concentrations showed substantial spatial variability throughout the river–treatment system. The mean concentrations of lead and zinc at the treatment plant inlet were 0.170 and 0.65 mg/L, respectively, with high coefficients of variation (231% for Pb and 115% for Zn). Reductions in Pb, Cd, and Zn concentrations at the plant outlet were limited and statistically insignificant (p > 0.05). Copper exhibited the greatest variability along the river continuum, indicating heterogeneous upstream inputs. Several samples exceeded WHO guideline values for lead by more than two orders of magnitude. The mean Hazard Index for children at the inlet (HI = 2.56) exceeded the acceptable threshold, with lead accounting for 97.7% of the total non-carcinogenic risk. Cadmium-related lifetime cancer risks remained within acceptable limits. Overall, the treatment plant reduced health risk indices by approximately 80%. Multivariate analysis revealed a strong correlation between zinc and copper (r = 0.87, p < 0.01), suggesting common pollution hotspots and shared anthropogenic sources.
Conclusion: Despite partial risk mitigation by the treatment plant, persistent lead contamination along the river–treatment continuum poses significant non-carcinogenic health risks to children. Effective source-control strategies and continuous water quality monitoring are essential to protect vulnerable populations and ensure the safety of treated drinking water.
Methods: In this analytical study, 61 water samples were collected along the river course and from the inlet and outlet of the treatment plant. Heavy metal concentrations were determined using a 797 Metrohm polarograph. Human health risks for children and adults were evaluated using chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI), and lifetime cancer risk (LCR). Multivariate statistical techniques, including correlation analysis and source apportionment, were applied to identify potential pollution sources.
Results: Heavy metal concentrations showed substantial spatial variability throughout the river–treatment system. The mean concentrations of lead and zinc at the treatment plant inlet were 0.170 and 0.65 mg/L, respectively, with high coefficients of variation (231% for Pb and 115% for Zn). Reductions in Pb, Cd, and Zn concentrations at the plant outlet were limited and statistically insignificant (p > 0.05). Copper exhibited the greatest variability along the river continuum, indicating heterogeneous upstream inputs. Several samples exceeded WHO guideline values for lead by more than two orders of magnitude. The mean Hazard Index for children at the inlet (HI = 2.56) exceeded the acceptable threshold, with lead accounting for 97.7% of the total non-carcinogenic risk. Cadmium-related lifetime cancer risks remained within acceptable limits. Overall, the treatment plant reduced health risk indices by approximately 80%. Multivariate analysis revealed a strong correlation between zinc and copper (r = 0.87, p < 0.01), suggesting common pollution hotspots and shared anthropogenic sources.
Conclusion: Despite partial risk mitigation by the treatment plant, persistent lead contamination along the river–treatment continuum poses significant non-carcinogenic health risks to children. Effective source-control strategies and continuous water quality monitoring are essential to protect vulnerable populations and ensure the safety of treated drinking water.
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