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. 2025 Jun 1;15(1):19196.
doi: 10.1038/s41598-025-04993-3.

Effect of lead zinc mineralization area on heavy metals accumulation and geochemical fractions of agricultural soils in Southwest China

Zhenglu Yu  1 , Xuexian Li  1   2 , Pan Wu  3 , Zhiwei Han  1 , Jian Zhu  1 , Manzhi Chen  1 , Zhuo Chen  4
Affiliations

Effect of lead zinc mineralization area on heavy metals accumulation and geochemical fractions of agricultural soils in Southwest China

Zhenglu Yu et al. Sci Rep. .

Abstract

Soils developed in karst regions are widely reported to exhibit high geological backgrounds of heavy metals (HMs) globally. However, due to unique geological conditions, there are both mineralized and/or altered areas of polymetallic minerals in karst areas, and whether the HMs concentrations of regional soil are affected by these mineralized and/or altered areas is far from enough attention at present. This study investigated the accumulation and chemical speciation of HMs in soils from typical lead-zinc mineralized zones in karst areas of Southwest China, using random forest (RF) modeling to identify key driving factors. The results indicated significant variability in HMs concentrations. Cr, Ni, and Cu levels were comparable to Guizhou Province's background values, while Cd, Pb, Zn, As, and Hg exceeded these values by 0.54 to 44.98 times. Notably, the accumulation of Cd, Pb, and Zn was particularly pronounced, with certain samples surpassing the risk control thresholds for agricultural land. Sequential extraction analysis revealed that Cd and Pb is predominantly found in reducible fractions, (40.61% and 36.49%, respectively), indicating strong bioavailability and potential mobility. RF analysis identified TFe₂O₃ and Al₂O₃ as key factors for the accumulation of As, Hg, Cr, Ni and Cu, while MnO and the distance to lead-zinc mineralization points (DL) significantly influenced Cd, Pb, and Zn levels. This study highlights that HMs accumulation is driven by carbonate rock parent materials and Cd, Pb, and Zn levels exacerbated by lead-zinc mineralization, offering a valuable insight for regional HMs management and control. Meanwhile, the research results can provide references for the geochemical accumulation mechanisms and risk management of soil HMs in mineralized areas (belts) worldwide.

Keywords: Chemical speciation; Heavy metals; High geochemical background; Pb-Zn mineralization area.

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Conflict of interest statement

Declarations. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Stratigraphic distribution of the Qingxudong Formation in Guizhou Province and the location of the sampling sites. (Adapted from Chen et al.).
Fig. 2
Fig. 2
Excess multiple of heavy metals in surface soils of the study area. (a) Reference values based on background soil values in Guizhou Province (CNEMC, 1990), (b) Reference values based on risk screening criteria for agricultural land (GB 15618 − 2018).
Fig. 3
Fig. 3
Graded statistical map of the geo-accumulation index (Igeo) for surface soils in the study area.
Fig. 4
Fig. 4
Geochemical speciation of Cr, Ni, Cu, Pb, Zn and Cd in soils (F1: acid-soluble fraction; F2: reducible fraction; F3: oxidizable fraction; F4: residual fraction).
Fig. 5
Fig. 5
Mobility factor (MF) and potential mobile fractions (PMF) of Cr, Ni, Cu, Pb, Zn and Cd in soils.
Fig. 6
Fig. 6
Ranking of important factors influencing the accumulation of heavy metals by random forest modeling.
Fig. 7
Fig. 7
Correlation and cluster analysis of heavy metals and soil properties in the study area (* represents P < 0.05, ** represents P < 0.01, *** represents P < 0.001).
See this image and copyright information in PMC

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