Heavy Metal Pollution and Safe Production Risks in Soil--Sugarcane Systems under High Geological Background Conditions

Heavy metal accumulation in agricultural soils represents a critical aspect of land degradation that threatens soil quality and crop safety. Addressing the current research gap in the characteristics of heavy metal contamination and their potential risks to sugar crops in high geological background areas, this study adopted a source-oriented approach to quantitatively assess the pollution characteristics and health risks of arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr), and mercury (Hg) in the soil–sugarcane system of cultivation areas with a high geological background in western Yunnan. By integrating positive matrix factorization (PMF) for source apportionment with Monte Carlo simulation for probabilistic health risk assessment, the contributions of different pollution sources and their associated health risks were quantitatively identified. The average Pb, Cd, and Cr contents were 11.00, 1.64, and 1.18 times higher than the background values in Yunnan Province, respectively, with Pb exhibiting a high coefficient of variation (117.08%), indicating significant anthropogenic disturbance. Contamination assessment identified Pb and Cd as primary pollutants, with a geological accumulation index of 1–4 and Cd composite risk index exceeding 150, indicating moderate to high ecological risk. Sugarcane exhibited Cd accumulation, amplifying the risk of transfer through the food chain. The PMF analysis revealed that the mixed source contributed the most to soil heavy metals(HMs) (63.2%), followed by the agricultural–industrial source (21.2%). Cd was mainly influenced by industrial and agricultural activities, Pb was primarily controlled by agricultural and parent material sources, and As was closely associated with the parent material source. Health risk assessments revealed non-carcinogenic risk(THQ) indices of 3.1 for adults and 6.8 for children, with Pb and As as the primary risk factors. The total carcinogenic risks (TCR) were 5.0× 10 -4 for adults and 7.9×10 -4 for children, indicating higher risks in the pediatric population, with As and Cd identified as the major carcinogenic elements. These results reveal a composite pollution pattern arising from the interplay of elevated geological background levels and human activities, providing a scientific basis for safe sugar crop production and regional health risk management under high geological background levels.