Abstract:

Heavy metal contamination constitutes a critical component of ecological risk evaluation. Concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were measured in 135 surface soil samples (0-20 cm)from a typical coal-mining area in Qujing, Yunnan Province, where a dual-index-dual-criteria evaluation system was developed to characterize pollution patterns. Key findings reveal that: (1)According to China’s Soil Environmental Quality Standard for Agricultural Land (GB 15618-2018), only localized Cd concentrations exceeded regulatory thresholds, while Cr, As, Hg, and Pb levels remained below risk control values; (2)The 2021 Nemerow comprehensive pollution index averaged 2.80 (moderate pollution), contrasting with a GB 15618-2018-based index mean of 1.58 (monitoring threshold). While regulated zones under GB 15618-2018 aligned with severe ecological risk areas identified by potential risk indices, discrepancies emerged in lower-risk classifications between ecological hazard indices and Nemerow evaluations. Traditional risk assessment methods, initially derived from case studies without standardized protocols, demonstrate limited compatibility with GB 15618-2018 frameworks, suggesting their validity requires further scrutiny; (3)Elevated pollution levels near coal gangue stockpiles necessitate prioritized regulation of coal production activities in high-risk zones, particularly targeting Cd contamination mitigation.

Key words: coal mining area, heavy metal contamination, risk evaluation