Atmospheric Deposition of Trace Toxic Metal Elements (TMEs) from Weathering of a Black Shale High Geological Background Areas in the Loushao Basin, Hunan Province, China: Pollution Characteristics and a Health Risk Assessment

This study is based on pollution assessment system and sustainability under a high geological background. The findings from atmospheric deposition research indicate that the exceedance rates for Cd, As, and Hg elements in black shale are 408%, 141%, and 220%, respectively. In atmospheric deposition, the concentrations of Cd, Hg, and Pb exceed the background values by 2.83, 3.29, and 4.08 times in dry conditions and by 3.6, 4.07, and 3.43 times in wet conditions. The difference between dry and wet deposition primarily reflects the concentration variations of Cd, Hg, and As. The distribution of Cd concentrations exceeding standards is widespread, covering over 71% of the total area, and shows a negative correlation with the enrichment patterns in weathered soils. Source analysis indicates that the contribution rates of PC1 for dry and wet deposition are 84.1% and 80.5%, respectively. This finding reveals that atmospheric deposition is significantly influenced by natural weathering processes, while anthropogenic factors exacerbate the overall pollution levels. The HI values for As, Hg, Pb, and Cr for both adults and children are all greater than 1, with the HI value for Pb in dry deposition reaching 13.5, indicating it poses the most severe health risk to children’s safety.