Heavy metals are considered one of the most serious threats to human health an‎d ecosystems due to their high toxicity an‎d long-term persistence in the environment. To identify environmental pollution caused by lead (Pb) an‎d zinc (Zn) elements, stream sediment data from the Khondab 1:100,000 geological map sheet, located between 49°00ʹ to 49°30ʹ E longitudes an‎d 34°00ʹ to 34°30ʹ N latitudes within the Markazi an‎d Hamadan provinces, were investigated. Outcrops of rock units in the Khondab sheet exhibit a generally uniform northwest-southeast trend. Cretaceous sedimentary rocks are predominantly found in the eastern half of the area, while Jurassic sedimentary rocks dominate the western half. Intrusive rocks outcrop is located in the central part of the eastern half, an‎d Quaternary sediments cover other parts. Since stream sediments represent materials from their upstream catchments, catchment basins corresponding to each sample were delineated for more precise pollution analysis. Using geological maps, chemical analysis data of elements, an‎d sample locations, the area of each catchment basins an‎d the proportion of effective lithologies within each basin were extracted. Based on this, the local single-element background concentration, derived from lithology using a weighted average method, was calculated an‎d used as the baseline concentration in sediment quality indices such as the contamination factor an‎d ecological risk index. Advanced multivariate statistical methods, including Pearson correlation matrix, factor analysis, an‎d hierarchical clustering, were applied to examine relationships an‎d correlations among variables. Pollution indices such as the geoaccumulation index, contamination factor, ecological risk index, pollution safety index, an‎d potential toxicity index were calculated, an‎d pollution maps for the elements were analyzed. The results showed that major pollution is concentrated in the southwestern part of the study area. This extensive pollution is likely caused by various human activities, including mining operations an‎d dust emissions from refineries. Subsequently, to rank polluted areas, erosion rates an‎d sediment discharge for each contaminated basin were calculated using the Erosion Potential Method (EPM), considering meteorological data (mean annual rainfall an‎d temperature coefficient), soil erosion intensity maps, an‎d basin characteristics such as length, perimeter, an‎d elevation difference. Finally, by integrating sediment pollution levels an‎d sediment discharge for each basin, polluted areas were ranked using the VIKOR multi-criteria decision-making method.

حسن طباطبائي

نادر فتحيان پور , سعيد پورمنافي