CSIR - National Institute of Oceanography, Regional Centre, Kochi 682 018, India.
CSIR - National Institute of Oceanography, Regional Centre, Kochi 682 018, India.
Mar Pollut Bull. 2021 Mar;164:112042. doi: 10.1016/j.marpolbul.2021.112042. Epub 2021 Jan 29.
This study investigates the influence of upwelling induced seasonal hypoxia in the sediment-water interface on the distribution, bioavailability and geochemical partitioning of selected trace metals in surficial sediments along the southwest coast of India based on two successive cruises. The first cruise was during the southwest monsoon (SWM) season when coastal waters exhibited intermittent bottom hypoxia due to upwelling. The second cruise during the northeast monsoon (NEM) season was characterised by a uniformly warm and well-oxygenated water column in the study region. The results showed that grain size, organic carbon and Fe are the major factors influencing the distribution of trace metals in the surface sediments. Based on the geochemical indices (contamination factor, enrichment factor and geo-accumulation factor), the study region appears to be moderately contaminated by Ni, Cr, and Pb. Based on the ecological risk assessment criteria, the enrichment of Pb, Cr and Ni may cause adverse effects on the benthic organisms. The fractionation studies demonstrated that the major pathway of metal deposition in the sediment is lithogenic. The data also showed that labile and organic fractions are the second dominant forms, while other fractions (exchangeable and carbonate) are insignificant. The consistency in the reactive Fe concentrations during SWM and NEM could be due to the absence of Fe dissolution in sediments under mild reducing condition (intermittent hypoxia). In addition to the above, an enrichment of organic matter also leads to increased deposition of trace metals in sediments. Conversely, the secondary phase enrichment factor and risk assessment code calculated based on the metal fractionation data indicated low risk and contamination along the southwest coast of India except for Zn that showed moderate contamination in some transects. The study provides the need for regular geochemical assessment to control metal pollution in the coastal environment, which is a major resource of the fishery.
本研究基于两次连续的巡航，调查了上升流引起的季节性海底缺氧对印度西南海岸表层沉积物中选定痕量金属的分布、生物可利用性和地球化学分配的影响。第一次巡航发生在西南季风（SWM）季节，由于上升流，沿海海域间歇性出现底部缺氧。第二次巡航发生在东北季风（NEM）季节，研究区域的水柱呈现温暖且含氧充足的特征。结果表明，粒径、有机碳和 Fe 是影响表层沉积物中痕量金属分布的主要因素。根据地球化学指标（污染因子、富集因子和地积累因子），研究区域似乎受到 Ni、Cr 和 Pb 的中度污染。根据生态风险评估标准，Pb、Cr 和 Ni 的富集可能对底栖生物产生不利影响。分馏研究表明，金属在沉积物中的沉积主要途径是生源。数据还表明，可利用和有机分数是第二主要形式，而其他分数（可交换和碳酸盐）则不重要。SWM 和 NEM 期间反应性 Fe 浓度的一致性可能是由于在温和还原条件（间歇性缺氧）下沉积物中没有 Fe 溶解。除此之外，有机物的富集也导致痕量金属在沉积物中的沉积增加。相反，基于金属分馏数据计算的次生相富集因子和风险评估代码表明，除了在一些横截线上显示中度污染的 Zn 外，印度西南海岸的污染程度低，风险低。本研究需要进行定期的地球化学评估，以控制沿海环境中的金属污染，这是渔业的主要资源。
