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<p>This study characterized the contamination, sources, and associated risks of heavy metals in the soil–rice system of the Nandu River Basin, a typical subtropical red soil region in China. Concentrations of eight heavy metals and metalloids (Cr, Ni, Cu, Zn, Pb, Cd, Hg, As) were determined in forty paired soil–rice samples. Pollution status and ecological risk were evaluated using the Nemerow integrated pollution index and Hakanson’s potential ecological risk index, respectively. Human health risks were assessed via a multi-pathway exposure model, and source apportionment was performed by integrating correlation analysis, principal component analysis (PCA), and the absolute principal component score–multiple linear regression (APCS-MLR) receptor model. Results showed that although most soil metals did not exceed national risk screening thresholds, Hg was severely enriched (6.44 times the local background level), posing a high ecological risk. In rice grains, Cr exceeded the food safety standard in 12% of samples. Rice consumption posed unacceptable carcinogenic risks from As and Cd, and unacceptable non-carcinogenic risks from As and Cr. The high spatial variability of Hg and Pb in rice (coefficient of variation, CV &gt; 140%) indicated strong anthropogenic influence. Source analysis identified four principal components. PC1 (47.3%) represented a mixed source of volcanic weathering and traffic/agricultural activities (Pb, Zn, Ni). PC2 (25.66%) reflected combined geogenic and agricultural inputs (As, Cu, Cr). PC3 (10.86%) was linked to electronics and traffic emissions (Hg). PC4 (7.32%) was attributed to fertilizer application (Cd). Health risk assessment showed children faced a 78% higher carcinogenic risk from oral soil As intake than adults. Dermal contact with soil Cr also posed a notable non-carcinogenic risk for adults. In conclusion, contamination in the basin originates from composite natural–anthropogenic sources. Hg is the primary driver of ecological risk, while Cr, As, and Cd in rice constitute key health concerns, especially for children. These findings provide a critical scientific basis for developing targeted risk management strategies for heavy metals in high‑background red soil agricultural regions.</p>

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Source analysis and human health risk assessment of heavy metals in farmland soil-rice system in Nandu River Basin, Zhanjiang City, Guangdong Province, China

  • 期刊论文

  • 发表日期：

    2026年1月7日

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  • Songying Luo,
  • Peixin Liang,
  • Xiaoxin Li,
  • Zengcai Li,
  • Tailin Zou,
  • Chengyang Li,
  • Xiuli Song

摘要

This study characterized the contamination, sources, and associated risks of heavy metals in the soil–rice system of the Nandu River Basin, a typical subtropical red soil region in China. Concentrations of eight heavy metals and metalloids (Cr, Ni, Cu, Zn, Pb, Cd, Hg, As) were determined in forty paired soil–rice samples. Pollution status and ecological risk were evaluated using the Nemerow integrated pollution index and Hakanson’s potential ecological risk index, respectively. Human health risks were assessed via a multi-pathway exposure model, and source apportionment was performed by integrating correlation analysis, principal component analysis (PCA), and the absolute principal component score–multiple linear regression (APCS-MLR) receptor model. Results showed that although most soil metals did not exceed national risk screening thresholds, Hg was severely enriched (6.44 times the local background level), posing a high ecological risk. In rice grains, Cr exceeded the food safety standard in 12% of samples. Rice consumption posed unacceptable carcinogenic risks from As and Cd, and unacceptable non-carcinogenic risks from As and Cr. The high spatial variability of Hg and Pb in rice (coefficient of variation, CV > 140%) indicated strong anthropogenic influence. Source analysis identified four principal components. PC1 (47.3%) represented a mixed source of volcanic weathering and traffic/agricultural activities (Pb, Zn, Ni). PC2 (25.66%) reflected combined geogenic and agricultural inputs (As, Cu, Cr). PC3 (10.86%) was linked to electronics and traffic emissions (Hg). PC4 (7.32%) was attributed to fertilizer application (Cd). Health risk assessment showed children faced a 78% higher carcinogenic risk from oral soil As intake than adults. Dermal contact with soil Cr also posed a notable non-carcinogenic risk for adults. In conclusion, contamination in the basin originates from composite natural–anthropogenic sources. Hg is the primary driver of ecological risk, while Cr, As, and Cd in rice constitute key health concerns, especially for children. These findings provide a critical scientific basis for developing targeted risk management strategies for heavy metals in high‑background red soil agricultural regions.