Distribution and speciation of selected metals in surface sediments, from the tropical Zuari estuary, central west coast of India

Abstract

Estuarine sediments are major reservoirs for the metals. Distribution and mobility of metals within estuaries depends strongly on their specific chemical form. In the present study, surface sediments from Zuari estuary, Goa were analysed by a sequential procedure for Fe, Mn, Cu, Zn, Cr and Co to determine their distribution in five geochemical phases (Exchangeable, carbonate, Fe-Mn oxide (reducible) organic bound (oxidisable) and residual). The total metal content, sand, silt, clay and organic carbon were also determined of the surface sediments. The total metal contents were found to be greater than the background concentrations of average shale values as well as to that of earlier studies indicating enrichment probably due to the anthropogenic origin of metals. The results obtained from sequential procedure showed that among the studied elements, Mn and Co are potentially available in the bioavailable fractions (exchangeable, carbonate and Fe-Mn oxide bound fractions) indicating their importance in toxicity whereas rest of the metals viz. Fe, Cu, Zn and to some extent Cr are largely available in residual phase although they are available in other fractions. The main source of metals to the estuary is mining and its associated activities in the study area. Chemical speciation by sequential extraction procedure has helped in assessing the mobility, bioavailability, diagenesis and toxicity of metals and hence giving a better insight into the ultimate fate of pollutants, which are introduced into the estuarine environment. To understand the risk of the metals to the sediment dwelling organisms the data were compared with the Sediment Quality Values (SQV) using SQUIRT. Also, correlation and Factor analysis were carried out to understand the associations of metals in the different fractions with sand, silt, clay, organic carbon and with other metals.

Statistical assessment of heavy metal distribution and contamination of beach sands of Antalya-Turkey: An approach to the multivariate analysis techniques

“…The considerable increase in the accumulation of heavy metals in the coastal environment in recent times attributed to anthropogenic activities has being of particular concern owing to their environmental persistence, biogeochemical recycling, and toxicity risks [25], [1], [8], [2], [29]. The contamination of soils and sediments by heavy metals is the most serious environmental problem and has significant implications on human health processes [7], [17].…”

Micronutrients and mangroves: Experimental evidence for copper limitation

“…The cycling of Cu as well as Zn and Mo in mangrove soils is not well understood, especially in relation to biological processes (Harbison 1986;Clark et al1998). Low dissolved metal concentrations in mangrove soils are due to a number of factors: (1) low chemical mobility (Gonz alez-Mendoza (2) high absorption to iron-and manganesecontaining minerals such as colloidal oxides (Deepti et al 2009); (3) low pH and redox; (4) precipitation as insoluble sulfides (Cuong and Obbard 2006;Machado et al 2008); (5) adsorbed on ion exchange sites of fine silt and clay particles; (6) adsorbed onto carbonate minerals (Clark et al 1998); and (7) incorporated into the lattice structure of clay. Since most mangrove soils are organic-rich, this condition enhances complexation with refractory organics, facilitating low availability of dissolved trace elements (Harbison 1986;Lacerda et al 1993;Lacerda 1997;Alongi et al 2004;Marchand et al 2011).…”

Environmental monitoring and assessment of heavy metals in surface sediments at Coleroon River Estuary in Tamil Nadu, India

“…All metals are slightly higher in this phase than the other phases. The low association of Mn in this phase is due to weak affinity of Mn for organics (Bendell-Young and Harvey 1992;Dessai and Nayak 2009). Higher concentration of Pb in this phase was originated from paints coated on fishing boats in the estuary.…”