Contamination and source-specific health risk assessment of soil heavy metals in the middle and upper reaches of the Heihe River Basin of China

Anthropogenic activities drive heavy metal contamination in soil, making source-specific apportionment essential for managing health risks in rapidly urbanizing areas. This study focuses on the novel task of quantifying health risks from specific sources of heavy metal contamination and visualizing the spatial patterns of human activities' impact on heavy metal contamination and health risks. It combined multiple analytical techniques, including pollution indices, health risk assessments, and bivariate local indicators of spatial association analysis. Additionally, the absolute principal component score-multiple linear regression model, integrated with a human health risk assessment, was employed to quantify health risks and evaluate the contributions of specific sources. Results revealed that Cd and As were at moderate contamination levels, while Zn, Cu, and Ni showed low contamination. Despite generally low contamination levels, moderately to heavily contaminated areas were identified in the southern region correlated with human activities. Although both non-carcinogenic and carcinogenic risks were low for both children and adults, Cr and As were still the main contributors to health risks, primarily through ingestion, with children being at a greater risk compared to adults. The health risks were primarily linked to four sources: traffic and mining, natural sources, agricultural activities, and industrial sources. Industrial (children: 27.47%; adults: 31.96%) and agricultural activities (children: 27.11%; adults: 24.01%) were the primary contributors to non-carcinogenic risks, while the carcinogenic risks were mainly contributed by agricultural activities (children: 40.21%; adults: 40.14%). Therefore, controlling industrial and agricultural activities is crucial to safeguarding public health during sustainable regional development.