Fractionation of Iron in River-Bed Sediments: Implications for the Assessment of Environmental Integrity of the Cauvery
Metals in the aquatic environments occur naturally as a result of weathering process and transport by various agents. Elevated levels of metals than the background values could be an indicator of environmental pollution, which in turn is a common phenomen
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Fractionation of Iron in River-Bed Sediments: Implications for the Assessment of Environmental Integrity of the Cauvery Delta Region, India S. Dhanakumar and R. Mohanraj
Abstract Metals in the aquatic environments occur naturally as a result of weathering process and transport by various agents. Elevated levels of metals than the background values could be an indicator of environmental pollution, which in turn is a common phenomenon since the era of industrialization and growing urbanization. Distribution of Fe and its fractionation in aquatic sediments has received considerable attention in view of its dominant role on regulating the abundances of many other heavy metals. In this context, the present study attempts to determine the fractionation of Fe in the surface sediments of the Cauvery River delta region during wet and dry periods. Other Physico-chemical parameters influencing fractionation such as Total Organic Carbon (TOC), Organic Matter (OM), pH in sediments were also studied. Total Iron concentration in the sediment samples ranged from 3,862 to 5,688 μg/g. Fractionation profile showed significant portion of Fe bound to Fe-Mn oxide (up to 28.6 %) and organic matter (up to 22 %) suggesting scavenging role of these sediment components in the river system. The study had also indicated the prevalence of little or insignificant input of Fe from anthropogenic sources.
6.1
Introduction
Many different species of metals occur in the aquatic environments. Speciation of metals and occurrences of different species of metals occur in various aquatic environments, primarily under the influences of prevailing physico-chemical conditions within an environment. The species of each metal is termed as a specific form of an element defined by its isotopic composition, electronic or oxidation state,
S. Dhanakumar • R. Mohanraj (*) Department of Environmental Management, Bharathidasan University, Tiruchirappalli 620 024, India e-mail: [email protected] Mu. Ramkumar (ed.), On a Sustainable Future of the Earth’s Natural Resources, Springer Earth System Sciences, DOI 10.1007/978-3-642-32917-3_6, # Springer-Verlag Berlin Heidelberg 2013
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complex or molecular structure and phase (Templeton et al. 2000). The concentration of a given metal in the sediment phase is equal to the summation of concentrations of its free ion, complexes and metal associated with various organic and inorganic matters. The mobility, bioavailability and toxicity of metals highly depend on the chemical forms that occur in the environment. Hence, conventional analysis of total metal concentrations for assessing bioavailability and toxicity of those metals to constrain on the environmental integrity is insufficient (Tessier et al. 1979). The concept of elemental fractionation dates back to 1954, when Goldberg introduced the concept of oxidized versus reduced, chelated versus free metal ions of trace elements in seawater (Jain 2004). Since then, fractionation studies attracted the attention of environmentalists and
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