ABSTRACT

The assessment of trace metal contamination in river sediments is crucial for suggesting effective strategies to protect aquatic ecosystem health. In this study, six toxic trace metals (As, Cd, Cr, Hg, Ni and Pb) in the surface sediments from the Old Brahmaputra River in Bangladesh were examined to evaluate the potential ecological risks. Sediment samples were collected in September 2018 and analysed by an atomic absorption spectrometer. Mean concentrations (mg/kg dw) of trace metals were in the order of Ni (43.49) > Cr (30.25) > Pb (14.29) > As (3.74) > Hg (0.16) > Cd (0.03). Spatially the sedimentary metals did not vary significantly. Source analyses revealed anthropogenic origin for most of the metals. The contamination factor, enrichment factor and geoaccumulation index (I_geo) revealed a low degree of contamination for all cases except Hg, which showed a moderate degree of contamination. According to the sediment quality guidelines and sediment screening values, only Cr, Hg and Ni were high enough to cause detrimental effects in aquatic organisms. The potential ecological risk factor (E_rⁱ) and potential ecological risk also revealed low to moderate ecological risk. Comprehensively, the river was in the uncontaminated to moderately contaminated level with low ecological risk.

摘要

河流沉积物中痕量金属污染的评估对于提出保护水生生态系统健康的有效策略至关重要。在这项研究中，对孟加拉国旧雅鲁藏布江表层沉积物中的六种有毒微量金属（As、Cd、Cr、Hg、Ni 和 Pb）进行了检测，以评估潜在的生态风险。沉积物样品于 2018 年 9 月收集，并通过原子吸收光谱仪进行分析。痕量金属的平均浓度 (mg/kg dw) 的顺序为 Ni (43.49) > Cr (30.25) > Pb (14.29) > As (3.74) > Hg (0.16) > Cd (0.03)。在空间上，沉积金属没有显着变化。来源分析揭示了大多数金属的人为来源。污染因子、富集因子和地累积指数（I _geo) 显示所有情况下的污染程度较低，但汞除外，汞显示中等程度的污染。根据沉积物质量指南和沉积物筛选值，只有 Cr、Hg 和 Ni 的含量高到足以对水生生物造成不利影响。潜在生态风险因子（E _r ⁱ）和潜在生态风险也显示出低至中度的生态风险。综合河流处于未污染至中度污染水平，生态风险较低。