Abstract:
Both mining activities and high geological background are considered the key factors causing heavy metal(loid)s accumulation in karst areas. To explore the influence of mining activities and soil parent material on the accumulation of soil heavy metal(loid)s in karst areas, this paper analyzed the distribution characteristics and main sources of heavy metal(loid)s (Cd, As, Pb, Cr, Ni) in 105 soil samples based on the combination of UNMIX model and spatial analysis method. The source identification results of UNMIX model were directly incorporated into GIS for spatial analysis, comparing the relationship between the dominant source spatial distribution of sampling sites and pollution source. The results showed that: (1) The average contamination of
w(Cd),
w(As),
w(Pb),
w(Cr),
w(Ni) in study area are 1.21, 19.4, 42.1, 80.9, 31.9 mg/kg, respectively. In detail, the pollution in the study area is mainly composed of Cd and As, and there is a slight Pb pollution at individual sites. (2) Parent material type, soil type, soil pH, and industrial influence are important factors affecting the accumulation of heavy metal(loid)s in the study area. Soils developed from carbonate rocks showed a higher average content of heavy metal(loid)s than other parent material, and alkaline soil also exhibited higher heavy metal(loid)s contents; The anthrosol exhibited a significant accumulation of Cd, As, and Pb; The co-enrichment of Cr and Ni has been reported to occur in the ferrallitic soil. (3) Source analysis showed that there were two sources of heavy metal(loid)s in the study area, which was soil parent material source (source 1) and industrial and agricultural mixed source (source 2), accounting for 68.45% and 31.55%, respectively. Source 1 played a dominant role in the contribution of Cr and Ni in the soil. The contribution of source 2 to As and Pb was higher than that of others. The accumulation of Cd was jointly dominated by the soil parent material source (source 1) and industrial and agricultural mixed source (source 2) in the study area. Our results indicated that high concentrations of heavy metal(loid)s were observed in the surface soil of the study area due to the inheritance of heavy metal(loid)s high concentration in carbonate rocks, and the secondary enrichment of pedogenic processes was another dominant factor of the enrichments for heavy metal(loid)s. Furthermore, metallurgical activities and directly river irrigation are aggravated the contamination of the surrounding soil.