PCA-PMF combined approach for source identification and risk quantification of heavy metals in legacy mining agricultural soils

Abstract

To investigate the heavy metal contamination in cultivated soils resulting from uncultivated coal mining activities, this study focused on paddy fields, vegetable plots, and uncultivated lands within the Yudong River Basin. Concentrations of six heavy metals—mercury (Hg), manganese (Mn), cadmium (Cd), arsenic (As), chromium (Cr), and lead (Pb)—were measured in the soil. Pollution index evaluation, positive matrix factorization (PMF), and health risk assessment were employed to analyze contamination characteristics, identify sources, and assess ecological and health risks. The results indicated that the mean concentrations of Hg and Cd in paddy soils were 0.15 and 1.15 mg·kg⁻¹, respectively; Cd in vegetable soils averaged 0.72 mg·kg⁻¹; and Hg in uncultivated lands was 0.14 mg·kg⁻¹. Source apportionment revealed that the six heavy metals in the cultivated soils primarily originated from natural sources, mixed agricultural and traffic activities, and industrial activities. Ecological risk assessment identified Hg and Cd as the major ecological risk factors. Health risk evaluation indicated that As in both paddy and vegetable soils represents the primary health risk factor. This study provides valuable insights for assessing heavy metal pollution in cultivated soils affected by uncultivated coal mines, supporting the development of remediation strategies, and evaluating the impact on local agricultural practices.