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<p>Toxic metals and metalloids (TMMs) in estuarine environments pose persistent threats to ecological integrity and public health due to their non-degradability and bioaccumulation potential. However, comprehensive, site-specific studies in the Karnaphuli Estuary are scarce, particularly those integrating risk indices and multivariate source analyses. This study aims to investigate the spatial distribution, contamination status, and ecological risk of ten TMMs (As, Se, Pb, Cd, Co, Cr, Cu, Mn, Ni, and Hg) in surface sediments from ten stations across three regions of the Karnaphuli Estuary, Bangladesh. Elemental concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). Results revealed marked spatial heterogeneity, with As concentrations ranging from 3.50 ± 2.43 to 6.48 ± 3.74&#xa0;mg/kg, Pb peaking (11.31 ± 4.01&#xa0;mg/kg) at lower stream, and Mn exhibiting the highest levels (423.55 ± 62.09&#xa0;mg/kg) at mid-stream. Enrichment factors indicated moderate to high enrichment for As (4.99–9.91) and Se (6.20–10.30), while other elements remained near background levels. The Pollution Load Index (PLI) was &lt; 1 at all sites, reflecting minimal overall contamination, whereas the Risk Index (RI) suggested low ecological risk (65.71–92.72), with localized hotspots in the mid-estuarine zone. Multivariate analyses (PCA) implicated industrial effluents and urban runoff as dominant sources, while Se and Hg exhibited distinct loading patterns, indicating different contamination pathways. This study provides an integrated spatial assessment of metal(loid) contamination in this estuary, highlighting both regional variability and pollution source differentiation. Although overall ecological risk is currently low, site-specific enrichment of toxic elements provided evidence for degradation of estuarine health.</p> Graphical Abstract <p>The graphical abstract depicted the overall workflow and principal findings of this investigation of hazardous metal(loid) contamination in the surface sediments of the Karnaphuli River Estuary, Bangladesh. The diagram on the right part illustrated significant anthropogenic sources of pollution, encompassing effluents from industrial establishments, household discharges, and residual pesticides from agricultural areas. These contaminants are carried into the estuary, where sediment samples were taken for examination. The middle part delineated the analytical methodology, commencing with sediment sample preparation (drying, grinding, and weighing), following by acid digestion, membrane filtration, and elemental measurement by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Ten trace metals and metalloids—As, Se, Pb, Cd, Co, Cr, Cu, Mn, Ni, and Hg—were examined to evaluate contamination levels. The lower portion encapsulates the findings of the multimetric pollution assessment: arsenic and selenium displayed moderate contamination levels, although other metals remained under baseline pollution criteria according to the Contamination Factor (CF) and Pollution Load Index (PLI). The Enrichment Factor (EF) study revealed substantial anthropogenic enrichment of selenium, while mercury exhibited the least enrichment. The total concentration of TMMs exhibited the following descending order: Mn &gt; Cr &gt; Ni &gt; Pb &gt; Cu &gt; Co &gt; As &gt; Se &gt; Cd &gt; Hg. This detailed visual presentation highlighted the importance of connecting pollution sources to ecological risk, providing essential insights into sediment quality and environmental health in a seasonally variable tropical estuary system.</p> <p></p>

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Spatial Dynamics and Ecological Risks of Sediment-Bound Metal(loid)s in a Heavily Industrialized Subtropical Estuary

  • 期刊论文

  • 发表日期：

    2025年9月11日

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  • Mohammad Belal Hossain,
  • Khadijatul Kubra Riya,
  • Sanjida Jahan Farjana,
  • Tabarok Bhuiyan,
  • Takaomi Arai,
  • Jimmy Yu,
  • Norhayati Ngah,
  • Md. Kamal Hossain

摘要

Toxic metals and metalloids (TMMs) in estuarine environments pose persistent threats to ecological integrity and public health due to their non-degradability and bioaccumulation potential. However, comprehensive, site-specific studies in the Karnaphuli Estuary are scarce, particularly those integrating risk indices and multivariate source analyses. This study aims to investigate the spatial distribution, contamination status, and ecological risk of ten TMMs (As, Se, Pb, Cd, Co, Cr, Cu, Mn, Ni, and Hg) in surface sediments from ten stations across three regions of the Karnaphuli Estuary, Bangladesh. Elemental concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). Results revealed marked spatial heterogeneity, with As concentrations ranging from 3.50 ± 2.43 to 6.48 ± 3.74 mg/kg, Pb peaking (11.31 ± 4.01 mg/kg) at lower stream, and Mn exhibiting the highest levels (423.55 ± 62.09 mg/kg) at mid-stream. Enrichment factors indicated moderate to high enrichment for As (4.99–9.91) and Se (6.20–10.30), while other elements remained near background levels. The Pollution Load Index (PLI) was < 1 at all sites, reflecting minimal overall contamination, whereas the Risk Index (RI) suggested low ecological risk (65.71–92.72), with localized hotspots in the mid-estuarine zone. Multivariate analyses (PCA) implicated industrial effluents and urban runoff as dominant sources, while Se and Hg exhibited distinct loading patterns, indicating different contamination pathways. This study provides an integrated spatial assessment of metal(loid) contamination in this estuary, highlighting both regional variability and pollution source differentiation. Although overall ecological risk is currently low, site-specific enrichment of toxic elements provided evidence for degradation of estuarine health.

Graphical Abstract

The graphical abstract depicted the overall workflow and principal findings of this investigation of hazardous metal(loid) contamination in the surface sediments of the Karnaphuli River Estuary, Bangladesh. The diagram on the right part illustrated significant anthropogenic sources of pollution, encompassing effluents from industrial establishments, household discharges, and residual pesticides from agricultural areas. These contaminants are carried into the estuary, where sediment samples were taken for examination. The middle part delineated the analytical methodology, commencing with sediment sample preparation (drying, grinding, and weighing), following by acid digestion, membrane filtration, and elemental measurement by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Ten trace metals and metalloids—As, Se, Pb, Cd, Co, Cr, Cu, Mn, Ni, and Hg—were examined to evaluate contamination levels. The lower portion encapsulates the findings of the multimetric pollution assessment: arsenic and selenium displayed moderate contamination levels, although other metals remained under baseline pollution criteria according to the Contamination Factor (CF) and Pollution Load Index (PLI). The Enrichment Factor (EF) study revealed substantial anthropogenic enrichment of selenium, while mercury exhibited the least enrichment. The total concentration of TMMs exhibited the following descending order: Mn > Cr > Ni > Pb > Cu > Co > As > Se > Cd > Hg. This detailed visual presentation highlighted the importance of connecting pollution sources to ecological risk, providing essential insights into sediment quality and environmental health in a seasonally variable tropical estuary system.