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<p>Mountain rivers in the Himalayas are highly susceptible to geogenic and anthropogenic influences. In this study, fourteen trace/heavy metals (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sr, Zn) were evaluated in the Chandra River, Lahaul–Spiti Region, during June–October 2022 to understand the dynamics of trace metals in the&#xa0;Himalayan waters. Water samples collected along the downstream flow of the Chandra&#xa0;river (Batal to Sangam), a major tributary of the Indus River, were analysed by ICP-OES and evaluated using pollution indices, and PCA analysis combined with PHREEQC speciation modelling. Findings revealed that aluminium (39–44&#xa0;μg L<sup>−1</sup>), arsenic (8–10.1&#xa0;μg L<sup>−1</sup>), and cadmium (3.0–4.0&#xa0;μg L<sup>−1</sup>) often exceeded BIS limits (Al: 30, As: 10, Cd: 3&#xa0;μg L<sup>−1</sup>) in the downstream sites (Sissu and Sangam) under the influence of drainage, recreational, and constructional activities. Upstream sites showed low pollution with heavy metal pollution index (HPI: 4.5 to 7.0), heavy metal evaluation index (HEI: &lt; 4.14), and Nemerow pollution index (NPI: &lt; 1.3), while downstream areas exhibited higher pollution with HPI rising upto 13 to 16.5 and ecological risk index (ERI) increasing from upstream (10–15) to downstream (30–42). Total&#xa0;Hazard Index (THI) values (&gt; 2) and ILCR (&gt; 1.62 × 10<sup>–4</sup>) at Sissu/Sangam exceed acceptable limits, indicating a potential public health risk. Three PCA factors (85.23% variance explained) separated heavy metals&#xa0;(HMs) sources into geogenic, agricultural, and other anthropogenic sources (tourism, traffic originated and erosion). Speciation modelling showed aluminium mainly as Al(OH)<sub>4</sub><sup>−</sup>, iron as Fe(OH)<sub>2</sub><sup>+</sup> or FeHCO<sub>3</sub><sup>+</sup>, along with&#xa0;zinc (Zn) and cadmium (Cd) as mobile sulfate and chloride complexes, while strontium was mostly SrSO<sub>4</sub> (&gt; 85%). Saturation indices (SI) show a distinct hydrogeochemical shift along the Chandra River, moving from strong undersaturation at&#xa0;upstream (Batal) to conditions nearing equilibrium or exhibiting supersaturation at&#xa0;downstream (Sissu and Sangam). Strong metal-anion correlations indicate carbonate and sulfate weathering control metal mobility. The ongoing presence of mobile Cd and Zn in the downstream underscores the need for continued monitoring.</p>

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Trace metal signatures and geochemical behaviour in the Chandra River: a combined multivariate and speciation analysis

  • 期刊论文

  • 发表日期：

    2025年11月3日

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  • Kalyan Biswal,
  • Janardhana Raju Nandimandalam,
  • Naveen Kumar

摘要

Mountain rivers in the Himalayas are highly susceptible to geogenic and anthropogenic influences. In this study, fourteen trace/heavy metals (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sr, Zn) were evaluated in the Chandra River, Lahaul–Spiti Region, during June–October 2022 to understand the dynamics of trace metals in the Himalayan waters. Water samples collected along the downstream flow of the Chandra river (Batal to Sangam), a major tributary of the Indus River, were analysed by ICP-OES and evaluated using pollution indices, and PCA analysis combined with PHREEQC speciation modelling. Findings revealed that aluminium (39–44 μg L−1), arsenic (8–10.1 μg L−1), and cadmium (3.0–4.0 μg L−1) often exceeded BIS limits (Al: 30, As: 10, Cd: 3 μg L−1) in the downstream sites (Sissu and Sangam) under the influence of drainage, recreational, and constructional activities. Upstream sites showed low pollution with heavy metal pollution index (HPI: 4.5 to 7.0), heavy metal evaluation index (HEI: < 4.14), and Nemerow pollution index (NPI: < 1.3), while downstream areas exhibited higher pollution with HPI rising upto 13 to 16.5 and ecological risk index (ERI) increasing from upstream (10–15) to downstream (30–42). Total Hazard Index (THI) values (> 2) and ILCR (> 1.62 × 10–4) at Sissu/Sangam exceed acceptable limits, indicating a potential public health risk. Three PCA factors (85.23% variance explained) separated heavy metals (HMs) sources into geogenic, agricultural, and other anthropogenic sources (tourism, traffic originated and erosion). Speciation modelling showed aluminium mainly as Al(OH)4−, iron as Fe(OH)2+ or FeHCO3+, along with zinc (Zn) and cadmium (Cd) as mobile sulfate and chloride complexes, while strontium was mostly SrSO4 (> 85%). Saturation indices (SI) show a distinct hydrogeochemical shift along the Chandra River, moving from strong undersaturation at upstream (Batal) to conditions nearing equilibrium or exhibiting supersaturation at downstream (Sissu and Sangam). Strong metal-anion correlations indicate carbonate and sulfate weathering control metal mobility. The ongoing presence of mobile Cd and Zn in the downstream underscores the need for continued monitoring.