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<p>Understanding how mercury (Hg) moves in paddy soils irrigated with coal acid mine drainage (AMD) is key to cleaning up contaminated fields. However, we do not fully understand how Hg moves in these soils. This study focuses on paddy soils from an AMD-impacted area in southwestern Guizhou, China, where three soil profiles were collected along the river impacted by AMD. The results indicate that the site with the highest Hg contamination was located midstream, where Hg concentrations were 7.2 times higher than the local background levels. The reason for this phenomenon may be related to the curvature of the river at the location of the site. Vertically, Hg contamination diminished with depth, likely due to long-term AMD irrigation (more Hg accumulating in topsoil over time). Hg speciation analysis revealed that sites closer to the coal mine had a higher percentage of residual Hg, while sites further downstream showed increased proportions of organically bound Hg and dissolved/exchangeable Hg. These findings are closely related to AMD irrigation and agricultural activities. In the surface soil, Hg was mainly bound to particulate organic matter (POM), accounting for 86.81%, while Hg bound to mineral-associated organic matter (MAOM) was comparatively lower, ranging from 6.53% to 22.24%. Notably, MAOM-Hg levels did not fluctuate significantly with soil depth, suggesting that POM in the surface layers plays a stronger role in Hg binding.</p>

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Mercury dynamics and speciation in paddy soils irrigated with acid mine drainage from abandoned coal mine: Insights from vertical profiling

  • 期刊论文

  • 发表日期：

    2026年4月20日

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  • Shasha Liu,
  • Longchao Liang,
  • Xiaohang Xu,
  • Yuling Kuang,
  • Le Wang,
  • Guangle Qiu,
  • Zhuo Chen,
  • Xian Dong,
  • Jialiang Han

摘要

Understanding how mercury (Hg) moves in paddy soils irrigated with coal acid mine drainage (AMD) is key to cleaning up contaminated fields. However, we do not fully understand how Hg moves in these soils. This study focuses on paddy soils from an AMD-impacted area in southwestern Guizhou, China, where three soil profiles were collected along the river impacted by AMD. The results indicate that the site with the highest Hg contamination was located midstream, where Hg concentrations were 7.2 times higher than the local background levels. The reason for this phenomenon may be related to the curvature of the river at the location of the site. Vertically, Hg contamination diminished with depth, likely due to long-term AMD irrigation (more Hg accumulating in topsoil over time). Hg speciation analysis revealed that sites closer to the coal mine had a higher percentage of residual Hg, while sites further downstream showed increased proportions of organically bound Hg and dissolved/exchangeable Hg. These findings are closely related to AMD irrigation and agricultural activities. In the surface soil, Hg was mainly bound to particulate organic matter (POM), accounting for 86.81%, while Hg bound to mineral-associated organic matter (MAOM) was comparatively lower, ranging from 6.53% to 22.24%. Notably, MAOM-Hg levels did not fluctuate significantly with soil depth, suggesting that POM in the surface layers plays a stronger role in Hg binding.