Indian Institute of Science Education and Research Mohali, 140306, Punjab, India.
Biodiversity and Paleobiology Group, Agharkar Research Institute, G.G. Agarkar Road, Pune 411004, Maharashtra, India.
J Contam Hydrol. 2024 Sep;266:104411. doi: 10.1016/j.jconhyd.2024.104411. Epub 2024 Jul 30.
The co-occurrence of microplastics (MPs) and heavy metals in aquatic systems has raised significant concerns, yet their relationship in freshwater ecosystems remains poorly understood. This study aims to evaluate the prevalence of MPs and factors controlling their distribution in both water and sediment in the Markanda River, Northwest India. MPs were extracted from sediment and water samples using density separation and classified through fluorescence microscopy and Raman spectroscopy. Metal concentrations in river water samples were analyzed using ICP-MS, and their correlation with MP abundance was explored. The results indicated the widespread occurrence of MP pollution across the Markanda River basin, with particle concentrations ranging from 10 to 530 particles L in surface water and 1330-4330 particles kg dry weight (dw) in sediment samples. The variability in MP abundance at sampling sites along the Markanda River courses results from factors such as the proximity of industrial establishments and human habitation, while the influence of grain size on MP distribution appears to be limited. Pellets (88.5 %) and fragments (8.5 %) were the most abundant types of MPs, with polyethylene (45.45 %) and polystyrene (30.9 %) being the dominant forms in water samples. The ICP-MS analysis of heavy metals in water samples indicated elevated levels of As (1.67 to 32.31 ppb) in downstream areas of the river system, influenced by human activities. While metals exhibited correlation with each other, there was a weak association, except for As, with the levels of MPs in the Markanda River. The SEM-EDX analyses to characterize chemical elements absorbed onto the surface of MP showed distinct variations in upstream and downstream sites, with the presence of elements such as Mn, Ni, Cr, Zn, As, Se, and Cu found in downstream areas. We conclude that MPs contaminated with heavy metals potentially threaten the ecological security of freshwater aquatic systems and highlight the importance of management action to reduce plastic pollution worldwide.
微塑料（MPs）和重金属在水生系统中的共存引起了人们的高度关注，但它们在淡水生态系统中的关系仍知之甚少。本研究旨在评估印度西北部 Markanda 河水中和沉积物中 MPs 的分布及其影响因素。通过密度分离从沉积物和水样中提取 MPs，并用荧光显微镜和拉曼光谱对其进行分类。采用 ICP-MS 分析河水样品中的金属浓度，并探讨其与 MP 丰度的相关性。结果表明，Markanda 河流域广泛存在 MP 污染，地表水的 MPs 浓度范围为 10 至 530 个颗粒/L，沉积物样品中为 1330 至 4330 个颗粒/kg 干重。Markanda 河沿线采样点的 MPs 丰度变化是由工业企业和人类居住等因素造成的，而粒径对 MPs 分布的影响似乎有限。颗粒（88.5%）和碎片（8.5%）是最丰富的 MPs 类型，其中聚乙烯（45.45%）和聚苯乙烯（30.9%）是水样中的主要形式。水样中重金属的 ICP-MS 分析表明，受人类活动影响，河流水体下游区域的砷（As）含量较高（1.67 至 32.31 ppb）。尽管金属之间相互关联，但除了 As 之外，与 Markanda 河 MPs 水平的关联较弱。对 MP 表面吸附的化学元素进行 SEM-EDX 分析表明，上游和下游站点的元素特征存在明显差异，下游区域存在 Mn、Ni、Cr、Zn、As、Se 和 Cu 等元素。综上所述，受重金属污染的 MPs 可能对淡水水生系统的生态安全构成威胁，强调了全球范围内采取管理行动减少塑料污染的重要性。
