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<p>Kasai River receives <i>inter alia</i> discharges of mining wastewaters, resulting in occasionally massive fish kills. This study quantified trace metals, including Hg, Pb, Cd, Cu, Sc, Zn, Ni, Cr, As, and Co, in surface sediments and edible fish collected on a stretch of the Kasaï River near the city of Bandundu. Metal analysis were performed using inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7700x) and an Advanced Mercury Analyzer (AMA-254) for total Hg. The river sediments showed an enrichment in metal concentrations, with Cu concentrations up to 57&#xa0;mg&#xa0;kg⁻<sup>1</sup>, Zn up to 279&#xa0;mg&#xa0;kg⁻<sup>1</sup>, Ni up to 70&#xa0;mg&#xa0;kg⁻<sup>1</sup>, Pb up to 69&#xa0;mg&#xa0;kg⁻<sup>1</sup>, and Hg &lt; 0.17&#xa0;mg&#xa0;kg⁻<sup>1</sup>, exceeding at some sites the Sediment Quality Guidelines adopted by Canada. Sediments acted as significant reservoirs for trace metals, with retention strongly influenced by organic matter and calcium carbonate content, while metal bioavailability and accumulation in fish reflected both geochemical and anthropogenic factors. Species-specific selenium-to-mercury molar ratios (0.5–31.7) indicated differential protective effects against Hg toxicity. Ecological risk indices indicated moderate to considerable risk (RI ≈ 170–207), with Hg, Cd, and Pb as major contributors. In fish muscle, Pb concentrations reached 1.6&#xa0;mg&#xa0;kg⁻<sup>1</sup>, Cd 0.7&#xa0;mg&#xa0;kg⁻<sup>1</sup>, and Hg 1.0&#xa0;mg&#xa0;kg⁻<sup>1</sup>, while other elements remained below safety thresholds. Human health risk assessment, including Estimated Daily Intake (EDI), Target Hazard Quotients (THQ), Hazard Index (HI ≤ 1.9), and Cancer Risk (CR ≤ 4.6 × 10⁻<sup>10</sup>), generally suggested low health risk for the moment. These findings highlight the need for continued monitoring of ecological and dietary exposure risks in the Kasai River basin.</p>

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Trace Metal Levels in Sediments and Muscle of Edible Fish Species from the Kasai River, Democratic Republic of the Congo

  • 期刊论文

  • 发表日期：

    2026年4月14日

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  • Henry M. Manza,
  • Guillaume M. Kiyombo,
  • Synthiche N. Kuna,
  • Fernando P. Carvalho,
  • John Poté,
  • Emmanuel K. Atibu,
  • Henry K. Mata

摘要

Kasai River receives inter alia discharges of mining wastewaters, resulting in occasionally massive fish kills. This study quantified trace metals, including Hg, Pb, Cd, Cu, Sc, Zn, Ni, Cr, As, and Co, in surface sediments and edible fish collected on a stretch of the Kasaï River near the city of Bandundu. Metal analysis were performed using inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7700x) and an Advanced Mercury Analyzer (AMA-254) for total Hg. The river sediments showed an enrichment in metal concentrations, with Cu concentrations up to 57 mg kg⁻1, Zn up to 279 mg kg⁻1, Ni up to 70 mg kg⁻1, Pb up to 69 mg kg⁻1, and Hg < 0.17 mg kg⁻1, exceeding at some sites the Sediment Quality Guidelines adopted by Canada. Sediments acted as significant reservoirs for trace metals, with retention strongly influenced by organic matter and calcium carbonate content, while metal bioavailability and accumulation in fish reflected both geochemical and anthropogenic factors. Species-specific selenium-to-mercury molar ratios (0.5–31.7) indicated differential protective effects against Hg toxicity. Ecological risk indices indicated moderate to considerable risk (RI ≈ 170–207), with Hg, Cd, and Pb as major contributors. In fish muscle, Pb concentrations reached 1.6 mg kg⁻1, Cd 0.7 mg kg⁻1, and Hg 1.0 mg kg⁻1, while other elements remained below safety thresholds. Human health risk assessment, including Estimated Daily Intake (EDI), Target Hazard Quotients (THQ), Hazard Index (HI ≤ 1.9), and Cancer Risk (CR ≤ 4.6 × 10⁻10), generally suggested low health risk for the moment. These findings highlight the need for continued monitoring of ecological and dietary exposure risks in the Kasai River basin.