Prevalence and Ecotoxicological significance of heavy metals in sediments of lower stretches of the Hooghly estuary, India

Debargha Chakraborty,Dipanwita Das,Alok Chandra Samal,Subash Chandra Santra

doi:10.52756/ijerr.2019.v19.001

Debargha Chakraborty, Dipanwita Das + Show 2 more

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https://doi.org/10.52756/ijerr.2019.v19.001

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Abstract

The concentration and distribution of selected eight heavy metals in five stations from lower stretches of the Hooghly estuary were studied to ascertain the level of anthropogenic contaminant loading resulting from the development of the region. Atomic absorption spectroscopy showed that the mean concentration of Fe, Zn, Cu, Ni, Pb, Cr, Cd and As (mg kg-1, dry weight,) ranged from 29950.70 – 39567.94, 61.45 – 98.83, 40.65 – 54.46, 25.44 – 42.78, 36.93 – 48.56, 29.07 – 46.35, BDL – 3.48 and 1.18 – 6.44 respectively. Pollution load index (PLI) and Index of geoaccumulation (Igeo) revealed overall low values but the enrichment factors (EFs) for Cd was typically high for three of the stations. Calculations based on Effect Range Low (ERL) and Threshold Effect Level (TEL) showed that the mean concentration of Cu, Ni and Cd and to some extent Pb exceeded these levels, indicating that there is chance of ecotoxicological effects on benthic organisms dwelling in this region. Inter-elemental relationship and cluster analysis revealed identical behavior of the elements during transport and distribution. The study will help to further the cause of environmental protection of this sensitive biorealm in conjunction with the need for development of the region.

Highlights

Mangroves are woody plants found in the habitat for a wide range of wild flora and tropical and subtropical latitudes which fauna, nursery ground for a variety of fishes provide various ecosystem goods and services, and are a source of wax, honey, timber and viz. protection against cyclones, storms and medicine
The aim of the study is to assess the status of contamination of the sediments by (1) comparing with sediment quality guidelines (SQGs) by US EPA, (2) computation of pollution indices viz Enrichment factor, Geoaccumulation index (Igeo) and Pollution Load Index (PLI); and (3) evaluating the ecotoxicological significance based on application of two sets of guidelines: Effect Range Low (ERL)/Effect range median (ERM) and Threshold Effect Level (TEL)/Probable effect level (PEL) and mean toxic units (Essien et al, 2009; Aloupi & Angelidis, 2001; MacDonald et al, 2000; Reddy et al, 2004; Selvaraj et al, 2004; Tomllinson et al, 1980; Woitke et al, 2003)
Sunderban estuarine region reveal that spatial distribution of metals in sediments are influenced by various processes like sedimentation, precipitation and flocculation

Summary

Introduction

Mangroves are woody plants found in the habitat for a wide range of wild flora and tropical and subtropical latitudes which fauna, nursery ground for a variety of fishes provide various ecosystem goods and services, and are a source of wax, honey, timber and viz. protection against cyclones, storms and medicine. Concerns arising out of multifarious developmental activities are the regular built-up of heavy metals to toxic levels in the aquatic environments, which find their way to the estuaries and to the oceans. It is because of their physico-chemical as well as biological properties that mangrove ecosystems tend to act both as sink and source of heavy metals (Evans et al, 2003; Harbison, 1986; Pekey, 2006; Rainey et al, 2003). Since it is difficult to separate the fractions of heavy metals coming from different sources, it is all the more vital to establish the expected natural background concentration level so that sediment quality indexes can be used to quantify anthropogenic inputs

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