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<p>This study presents the first comprehensive assessment of heavy metal contamination, ecological risk, and potential human health implications in alluvial sediments from the Mbam and Noun Rivers in Central Cameroon. Eighty-two sediment samples were collected and analyzed by inductively coupled plasma–mass spectrometry (ICP–MS) to determine the concentrations of Cr, V, Ni, Cu, Zn, Pb, Sn, U, and Th. The results were compared with upper continental crust (UCC) background values and ecotoxicological benchmarks, including threshold effect level (TEL), probable effect level (PEL), effect range—low (ERL), and effect range—median (ERM). Several contamination and ecological indices are as follows: contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), pollution load index (PLI), and ecological risk indices (Er, RI) were used to evaluate pollution intensity and its environmental implications. In the Mbam River, metal concentrations generally decreased upstream, following the order V &gt; Cr &gt; Zn &gt; Ni &gt; Cu &gt; Pb &gt; Th &gt; Sn &gt; U, with moderate contamination (<i>CF</i> = 1.2–3.5) and PLI values between 1.3 and 1.5, indicating diffuse anthropogenic influence. In contrast, the Noun River displayed extremely high uranium and vanadium enrichment (<i>CF₍U₎</i> &gt; 5; <i>EF₍U₎</i>≈3.8), resulting in RI values up to 240, which denote considerable to very high ecological risk. Human health indices revealed hazard index (HI) values below 1 for all sites, indicating no immediate non-carcinogenic risk, though children showed higher exposure (HI_child = 0.19–0.34) than adults. Total carcinogenic risk (TCR) values (10<sup>−⁶</sup>–10<sup>−4</sup>) remained within the acceptable range but were highest at downstream Mbam sites, reflecting cumulative exposure to Cr (VI), Ni, and U. These findings indicate that metal enrichment in both rivers stems from the weathering of uranium-bearing lithologies combined with localized anthropogenic activities, including artisanal mining and agricultural runoff. Continuous monitoring and integrated watershed management are recommended to mitigate ecological degradation and long-term health risks in the Mbam–Noun River system.</p>

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Assessment of heavy metal contamination and ecological risk in alluvial sediments along the Mbam and Noun Rivers, Cameroon (SW Africa)

  • 期刊论文

  • 发表日期：

    2025年12月24日

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  • Armel Zacharie Ekoa Bessa,
  • Elvine Paternie Edjengté Doumo,
  • Victorine Ambassa Bela,
  • Marie Ganmo Koutchouo,
  • Patrice Roland Liyouck,
  • Amaya Adama

摘要

This study presents the first comprehensive assessment of heavy metal contamination, ecological risk, and potential human health implications in alluvial sediments from the Mbam and Noun Rivers in Central Cameroon. Eighty-two sediment samples were collected and analyzed by inductively coupled plasma–mass spectrometry (ICP–MS) to determine the concentrations of Cr, V, Ni, Cu, Zn, Pb, Sn, U, and Th. The results were compared with upper continental crust (UCC) background values and ecotoxicological benchmarks, including threshold effect level (TEL), probable effect level (PEL), effect range—low (ERL), and effect range—median (ERM). Several contamination and ecological indices are as follows: contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), pollution load index (PLI), and ecological risk indices (Er, RI) were used to evaluate pollution intensity and its environmental implications. In the Mbam River, metal concentrations generally decreased upstream, following the order V > Cr > Zn > Ni > Cu > Pb > Th > Sn > U, with moderate contamination (CF = 1.2–3.5) and PLI values between 1.3 and 1.5, indicating diffuse anthropogenic influence. In contrast, the Noun River displayed extremely high uranium and vanadium enrichment (CF₍U₎ > 5; EF₍U₎≈3.8), resulting in RI values up to 240, which denote considerable to very high ecological risk. Human health indices revealed hazard index (HI) values below 1 for all sites, indicating no immediate non-carcinogenic risk, though children showed higher exposure (HI_child = 0.19–0.34) than adults. Total carcinogenic risk (TCR) values (10−⁶–10−4) remained within the acceptable range but were highest at downstream Mbam sites, reflecting cumulative exposure to Cr (VI), Ni, and U. These findings indicate that metal enrichment in both rivers stems from the weathering of uranium-bearing lithologies combined with localized anthropogenic activities, including artisanal mining and agricultural runoff. Continuous monitoring and integrated watershed management are recommended to mitigate ecological degradation and long-term health risks in the Mbam–Noun River system.