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<p>Dissolved, particulate, and sediment-bound heavy metals were investigated along the Indian National Waterway-3 (NW-3), encompassing ecologically significant estuarine and backwater systems, including the Ashtamudi Lake estuary and Cochin estuary (Ramsar sites), to evaluate their seasonal distribution, partitioning behaviour, contamination status, and ecological implications. Water, suspended particulate matter, and sediments were collected from 17 stations along the NW-3 corridor and analysed for heavy metals, including Fe, Mn, Cr, Co, Ni, Cu, Zn, Cd, and Pb. Among the dissolved metals, Fe (17.51–350.63&#xa0;µg/L), Zn (3.63–43.86&#xa0;µg/L), and Cu (0.64–30.25&#xa0;µg/L) were predominant. In contrast, suspended particulate matter and sediments exhibited considerable enrichment of Zn (111.35–4012.49&#xa0;mg/kg), Cd (0.30–2.82&#xa0;mg/kg), and Co (6.55–582.23&#xa0;mg/kg), particularly in the lower estuarine reaches influenced by intense urban and industrial activities. Elevated logKd values (&gt; 3) indicated a strong affinity of metals towards particulate phases, governed by physicochemical parameters such as salinity, pH, dissolved oxygen, and organic matter content. Geochemical indices, including Enrichment Factor (EF), Contamination Factor (CF), Geo-accumulation Index (Igeo), Pollution Load Index (PLI) and Potential Ecological Risk Index (PERI), collectively indicated moderate to severe contamination by Cd and Zn, with comparatively higher pollution loads observed in the downstream regions of the NW-3. These elevated contamination levels are likely associated with untreated urban sewage, industrial effluent discharge from the Periyar River and Muvattupuzha River catchments, and shipbuilding-related activities. Principal Component Analysis (PCA) and correlation analysis revealed the combined influence of lithogenic processes, particularly Fe–Mn oxyhydroxide scavenging, and anthropogenic inputs, including agricultural runoff, industrial discharge, and urban effluents, on the distribution and accumulation of metals. Comparison with the National Oceanic and Atmospheric Administration Sediment Quality Guidelines (SQGs) and Toxic Risk Index (TRI) demonstrated that Cd and Cr concentrations frequently exceeded the Threshold Effect Level (TEL) and Effects Range-Low (ERL) values, indicating potential ecological risks and possible adverse effects on benthic organisms. Overall, the study demonstrates that suspended particulates and sediments act as both major sinks and secondary sources of heavy metals within the NW-3 system. The findings emphasise the urgent need for continuous environmental monitoring, effective pollution control strategies, and sustainable management practices to protect this ecologically sensitive and economically important inland waterway system.</p>

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Geochemical and ecological assessment of heavy metals in a National Waterway in South India

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月9日

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  • A. S. Ragi,
  • T. R. Gireeshkumar,
  • K. Habeeb Rahman,
  • Snigtha Snigtha,
  • C. Abhina,
  • T. P. Muhammed Aquib,
  • C. Nayana,
  • G. D. Martin

摘要

Dissolved, particulate, and sediment-bound heavy metals were investigated along the Indian National Waterway-3 (NW-3), encompassing ecologically significant estuarine and backwater systems, including the Ashtamudi Lake estuary and Cochin estuary (Ramsar sites), to evaluate their seasonal distribution, partitioning behaviour, contamination status, and ecological implications. Water, suspended particulate matter, and sediments were collected from 17 stations along the NW-3 corridor and analysed for heavy metals, including Fe, Mn, Cr, Co, Ni, Cu, Zn, Cd, and Pb. Among the dissolved metals, Fe (17.51–350.63 µg/L), Zn (3.63–43.86 µg/L), and Cu (0.64–30.25 µg/L) were predominant. In contrast, suspended particulate matter and sediments exhibited considerable enrichment of Zn (111.35–4012.49 mg/kg), Cd (0.30–2.82 mg/kg), and Co (6.55–582.23 mg/kg), particularly in the lower estuarine reaches influenced by intense urban and industrial activities. Elevated logKd values (> 3) indicated a strong affinity of metals towards particulate phases, governed by physicochemical parameters such as salinity, pH, dissolved oxygen, and organic matter content. Geochemical indices, including Enrichment Factor (EF), Contamination Factor (CF), Geo-accumulation Index (Igeo), Pollution Load Index (PLI) and Potential Ecological Risk Index (PERI), collectively indicated moderate to severe contamination by Cd and Zn, with comparatively higher pollution loads observed in the downstream regions of the NW-3. These elevated contamination levels are likely associated with untreated urban sewage, industrial effluent discharge from the Periyar River and Muvattupuzha River catchments, and shipbuilding-related activities. Principal Component Analysis (PCA) and correlation analysis revealed the combined influence of lithogenic processes, particularly Fe–Mn oxyhydroxide scavenging, and anthropogenic inputs, including agricultural runoff, industrial discharge, and urban effluents, on the distribution and accumulation of metals. Comparison with the National Oceanic and Atmospheric Administration Sediment Quality Guidelines (SQGs) and Toxic Risk Index (TRI) demonstrated that Cd and Cr concentrations frequently exceeded the Threshold Effect Level (TEL) and Effects Range-Low (ERL) values, indicating potential ecological risks and possible adverse effects on benthic organisms. Overall, the study demonstrates that suspended particulates and sediments act as both major sinks and secondary sources of heavy metals within the NW-3 system. The findings emphasise the urgent need for continuous environmental monitoring, effective pollution control strategies, and sustainable management practices to protect this ecologically sensitive and economically important inland waterway system.