Ecological consideration of trace element contamination in sediment cores from Sundarban wetland, India

Abstract

This article reports on the concentration of selected trace elements (Mn, Zn, Cr, Cu, Ba, As, B, V, and Hg) and major elements (Fe and Al) from the intertidal sediment cores from Sundarban wetland, India. This is a typical meso-macrotidal estuarine area affected by domestic and industrial activities located upstream. The overall concentrations range is low to moderate, indicating the environmental conditions in the outfall zone (grain size, hydrodynamic regime, and confinement), which favors the in situ accumulation of pollutants. The extent of contamination from trace elements in Sundarban core sediments is evaluated through a two-pronged approach: (i) by determining the metal enrichment in the sediments through the calculation of Pollution Load Index (PLI), Enrichment Factor (EF) and Index of Geoaccumulation (I geo ), and (ii) by defining a potential level of biological risk by the use of quality criteria such as Threshold Effect Level (TEL) and Effects Range-Low (ERL) benchmarks. On the basis of the calculated indices, sediments are particularly enriched with Cr, Cu, B, V, and As. Those enrichments seem to be due to the fine granulometry of the regions with Fe and Mn oxihydroxides being the main metal carriers. Trace Elements input to the Sundarban wetland need to be kept under strict control in future specially with reference to As since, according to TEL and ERL benchmarks, it already appears to be associated with a potential biological risk.

Sedimentation of metals in Sundarban mangrove ecosystem: Dominant drivers and environmental risks

“…Wastewater from those industries and agricultural runoff add the bulk of heavy metals in this estuary (Guhathakurta and Kaviraj, 2000;Turner, 2000;Saha et al, 2001;DeMahiques et al, 2013). Reports suggested bioaccumulation and biomagnification of metals in plants, bottom-dwelling fauna, commercially important fish, and shellfish, indicating a threat to this ecosystem (Ramanathan et al, 2009;Alam et al, 2010;Silva Filho et al, 2011;Barua et al, 2011;Chaudhuri et al, 2014;Kader and Sinha, 2018). Control of trace metals released from upstream, and integrated ecotoxicological assessment are warranted for identifying and averting pollution in this stressed and sensitive estuarine environment.…”

“…Several studies investigated heavy metals in sediment and biota in Sundarban estuarine ecosystem during last few decades showing wide variations in their findings (Guhatahkurta and Kaviraj, 2000;Mukerjee et al, 2009;Rajkumar et al, 2012;Chakraborty et al, 2014;Kumar et al, 2016;Kader and Sinha, 2018;Mitra et al, 2018;Ranjan et al, 2018). But work on sedimentation process history and its relationship with metal accumulation is very limited (Jonathan et al, 2010;Silva Filho et al, 2011;Banerjee et al, 2012;Rajkumar et al, 2014;Kumar and Ramanathan, 2015).…”