Institute for Ocean Management, Anna University, Chennai 600025, India.
Environ Geochem Health. 2012 Feb;34(1):27-42. doi: 10.1007/s10653-011-9388-0. Epub 2011 Apr 3.
Four sediment cores were collected from selected locations of Sundarbans mangroves and Hooghly estuary, northeast coast of India to establish (210)Pb geochronology and trace metal distribution in sediments. Core sites were chosen to reflect a matrix of variable anthropogenic input and hydrological conditions. The vertical distribution of (210)Pb(xs) ((210)Pb(total)-(226)Ra) provided reliable geochronological age to calculate the mass accumulation rates and historic trace element inputs and their variations. The mass accumulation rates ranged from 0.41 g cm(-2) year(-1) (estuarine region) to 0.66 g cm(-2) year(-1) (mangrove region). Both in mangroves and estuarine systems, Fe-Mn oxy-hydroxides are observed to be a major controlling factor for trace metal accumulation when compared to organic carbon. Core collected from Hooghly estuary shows less contamination when compared to the mangrove region due to high energy and mostly coarse grained. Fe-normalized enrichment factors (EFs) of trace metals were calculated based on crustal trace element abundances. The EFs are typically >1 for Cd, Pb, Co, and Cu indicating that these metals are highly enriched while other metals such as Zn, Ni, Cr, and Mn show no enrichment or depletion. Both Sundarbans mangroves and Hooghly estuary have been receiving considerable pollution loads from anthropogenic sources such as industrial, domestic, and shipping activities in recent times, indicating high concentration of metals in the top few layers. This study suggests that the variation in trace metals content with depth or between mangrove and estuarine system results largely from metal input due to anthropogenic activities rather than diagenetic processes.
从印度东北部恒河三角洲的孙德尔本斯红树林和胡格利河口选取了四个沉积物岩芯，以建立（210）Pb 地球化学年代学和沉积物中痕量金属的分布。选择岩芯位置以反映不同人为输入和水文条件的矩阵。（210）Pb(xs)（（210）Pb（总）-（226）Ra）的垂直分布为计算质量积累速率和历史痕量元素输入及其变化提供了可靠的地质年代。质量积累速率范围从 0.41 g cm(-2) year(-1)（河口区）到 0.66 g cm(-2) year(-1)（红树林区）。与有机碳相比，在红树林和河口系统中，铁锰水氧化物被观察为痕量金属积累的主要控制因素。与红树林区相比，从胡格利河口采集的岩芯受到的污染较小，因为能量较高且主要为粗粒。基于地壳痕量元素丰度计算了痕量金属的 Fe 归一化富集因子（EF）。EF 值通常大于 1，表明 Cd、Pb、Co 和 Cu 等金属高度富集，而 Zn、Ni、Cr 和 Mn 等其他金属则没有富集或耗尽。孙德尔本斯红树林和胡格利河口近年来一直受到人为活动（如工业、家庭和航运活动）带来的大量污染负荷，表明顶部几层金属浓度较高。本研究表明，痕量金属含量随深度或红树林和河口系统之间的变化主要是由于人为活动引起的金属输入，而不是成岩作用。
