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<p>Manganese (Mn) contamination in agricultural systems is usually attributed to mining or industrial sources, but hydrologically connected catchments can transfer geogenic Mn to staple crops through irrigation. This study characterized Mn transfer from a mine-influenced, recently disturbed upland to irrigation water, stream sediment, paddy soils, rice tissues, and screening-level dietary exposure in a semi-enclosed catchment in Ilgwang, Busan, South Korea. Surface water and stream sediment were monitored over four agricultural periods in 2021, and paddy soils and rice were sampled from four sequential irrigation zones (P1–P4). Mn was measured by ICP-OES, and solid-phase partitioning was assessed by the modified BCR sequential extraction procedure. Dissolved Mn was strongly enriched along the disturbed-upland drainage pathway (main-flow mean 4.55 ± 1.61&#xa0;mg/L) relative to tributary inputs (0.16 ± 0.27&#xa0;mg/L). Stream sediments approached 20,000&#xa0;mg/kg with more than 97% in non-residual fractions, and paddy soils were enriched up to a field-mean of approximately 1,050&#xa0;mg/kg (67–83% non-residual). A screening-level, dissolved-Mn flux analysis indicated that the upper paddy zone retained 49.5–56.6% of the seasonal irrigation-derived Mn within the soil–sediment system. Rice grain Mn ranged from 90.64 to 171.47&#xa0;mg/kg (highest at P3), greatly exceeding typical background levels (1–10&#xa0;mg/kg). Screening-level hazard quotients exceeded 1 in all zones and remained above 1 for young children even under a conservative 70% bioaccessibility reduction. Because the source was predominantly geogenic and bioaccessibility, cultivar, redox, and pre-disturbance baselines were not directly quantified, these results document an irrigation-mediated exposure pathway rather than a proven causal effect of land disturbance. </p>

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Irrigation-mediated transfer of geogenic manganese to paddy soils and rice grain in a mine-influenced catchment: a screening-level dietary exposure assessment

  • 期刊论文

  • 发表日期：

    2026年7月20日

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  • Junyong Heo,
  • Taeyong Kim,
  • Hyemin Park,
  • Tae-jung Ha,
  • Nakyung Jeon,
  • Minjune Yang

摘要

Manganese (Mn) contamination in agricultural systems is usually attributed to mining or industrial sources, but hydrologically connected catchments can transfer geogenic Mn to staple crops through irrigation. This study characterized Mn transfer from a mine-influenced, recently disturbed upland to irrigation water, stream sediment, paddy soils, rice tissues, and screening-level dietary exposure in a semi-enclosed catchment in Ilgwang, Busan, South Korea. Surface water and stream sediment were monitored over four agricultural periods in 2021, and paddy soils and rice were sampled from four sequential irrigation zones (P1–P4). Mn was measured by ICP-OES, and solid-phase partitioning was assessed by the modified BCR sequential extraction procedure. Dissolved Mn was strongly enriched along the disturbed-upland drainage pathway (main-flow mean 4.55 ± 1.61 mg/L) relative to tributary inputs (0.16 ± 0.27 mg/L). Stream sediments approached 20,000 mg/kg with more than 97% in non-residual fractions, and paddy soils were enriched up to a field-mean of approximately 1,050 mg/kg (67–83% non-residual). A screening-level, dissolved-Mn flux analysis indicated that the upper paddy zone retained 49.5–56.6% of the seasonal irrigation-derived Mn within the soil–sediment system. Rice grain Mn ranged from 90.64 to 171.47 mg/kg (highest at P3), greatly exceeding typical background levels (1–10 mg/kg). Screening-level hazard quotients exceeded 1 in all zones and remained above 1 for young children even under a conservative 70% bioaccessibility reduction. Because the source was predominantly geogenic and bioaccessibility, cultivar, redox, and pre-disturbance baselines were not directly quantified, these results document an irrigation-mediated exposure pathway rather than a proven causal effect of land disturbance.