Spatial Characteristics and ecological risk evaluations of soil heavy metals in an abandoned mining area in Yunnan, China

Soil heavy metal pollution in mining areas has become a critical globally environmental issue in recent years. Systematic field research and a series of laboratory experiments were conducted to investigated the soil contamination and ecological risks at a representative mining site in Yunnan Province. A total of 198 sets of data on 6 heavy metal elements were collected and analyzed from 11 sampling points in three deep strata. The mean concentration of six heavy metals (Cu, Ni, Pb, Cd, As, Hg) all exceeded background levels, ranked as Hg < Cd < As < Ni < Pb < Cu. Principal components analysis identified two major contamination sources: (1) Cu-Ni-Cd associations (geogenic) and (2) Pb-As-Hg clustering (industrial). Pollution factors (Cf = 0.46 - 42.93) varied significantly, indicating distinct anthropogenic disturbance levels. Spatial differentiation was evident in the Pollution Load Index (PLI) analysis. Both individual ecological risk indices (Eri = 1.41 - 1717.2) and the comprehensive potential ecological risk index (RI = 111 - 29,373) exceeded thresholds, confirming elevated ecosystem risks. The study provided reference framework for the contamination evaluation and supported the pollution controlling in mining sites.