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<p>The rapid acceleration of global urbanization and intensified mining activities has led to severe heavy metal pollution in river systems. The Longjiang River in Guangxi, South China, a major tributary of the Pearl River system, is situated in a region with a long history of intensive mining and smelting. Although this watershed has experienced multiple historical contamination incidents, research on the quantitative source apportionment and screening-level health risks of dissolved heavy metals remains insufficient. This study systematically investigated dissolved heavy metal concentrations during wet and dry seasons to determine spatio-temporal distributions, quantify anthropogenic versus natural sources, and assess human health risks under clearly stated exposure and toxicity assumptions. Results indicated that most heavy metal concentrations were comparable to global river averages, but localized hotspots classified as “moderate” to “heavy pollution” persisted. Positive Matrix Factorization (PMF), interpreted together with field conditions, local industrial distributions, and geochemical marker combinations, identified Sb-Cu mining and smelting and Pb–Zn industrial/mining activities with municipal sewage as the dominant sources, contributing 63.6% of the load in the wet season and 74.6% in the dry season. Anthropogenic metals such as As, Sb, Zn, Cd, and Pb showed no significant seasonal variations, implying that episodic inputs and rainfall-driven flushing may obscure simple dilution patterns. The screening-level health assessment indicated that Sb was the primary contributor to non-carcinogenic risk, whereas As dominated carcinogenic risk, with oral ingestion contributing more than 99% of exposure. Total carcinogenic risk exceeded 10<sup>−6</sup> at all sites and exceeded the 10<sup>−4</sup> risk-management benchmark in 4.3% of child and 2.2% of adult scenarios. These findings suggest that, despite remediation progress, priority hotspots remain in specific sub-regions. Future management should shift from general regulation to targeted, source-specific control, prioritizing Sb and As reduction in identified hotspots and strengthening drinking-water safeguards for sensitive populations, especially children.</p> Graphical abstract <p></p>

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From general remediation to targeted control: a heavy metal management strategy for the Longjiang River, South China, based on source apportionment and risk assessment

  • 期刊论文

  • 发表日期：

    2026年7月17日

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  • Xiaolong Lan,
  • Zengping Ning,
  • Yin Li,
  • Qingxiang Xiao,
  • Haiyan Chen,
  • Wenjie Lin,
  • Yanlong Jia,
  • Zhongwen Huang,
  • Tangfu Xiao

摘要

The rapid acceleration of global urbanization and intensified mining activities has led to severe heavy metal pollution in river systems. The Longjiang River in Guangxi, South China, a major tributary of the Pearl River system, is situated in a region with a long history of intensive mining and smelting. Although this watershed has experienced multiple historical contamination incidents, research on the quantitative source apportionment and screening-level health risks of dissolved heavy metals remains insufficient. This study systematically investigated dissolved heavy metal concentrations during wet and dry seasons to determine spatio-temporal distributions, quantify anthropogenic versus natural sources, and assess human health risks under clearly stated exposure and toxicity assumptions. Results indicated that most heavy metal concentrations were comparable to global river averages, but localized hotspots classified as “moderate” to “heavy pollution” persisted. Positive Matrix Factorization (PMF), interpreted together with field conditions, local industrial distributions, and geochemical marker combinations, identified Sb-Cu mining and smelting and Pb–Zn industrial/mining activities with municipal sewage as the dominant sources, contributing 63.6% of the load in the wet season and 74.6% in the dry season. Anthropogenic metals such as As, Sb, Zn, Cd, and Pb showed no significant seasonal variations, implying that episodic inputs and rainfall-driven flushing may obscure simple dilution patterns. The screening-level health assessment indicated that Sb was the primary contributor to non-carcinogenic risk, whereas As dominated carcinogenic risk, with oral ingestion contributing more than 99% of exposure. Total carcinogenic risk exceeded 10−6 at all sites and exceeded the 10−4 risk-management benchmark in 4.3% of child and 2.2% of adult scenarios. These findings suggest that, despite remediation progress, priority hotspots remain in specific sub-regions. Future management should shift from general regulation to targeted, source-specific control, prioritizing Sb and As reduction in identified hotspots and strengthening drinking-water safeguards for sensitive populations, especially children.

Graphical abstract