Essay On Heavy Metals

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5. HEAVY METAL BIOAVAILABILITY AND SEASONAL VARIATION IN WATER AND SEDIMENT
5.1 INTRODUCTION
Sediments are known to be “Trace element traps” because they eventually bind almost all the contaminants which enter the aquatic environment. Heavy metals in sediments can lead to greater environmental problems when the contaminated sediments are resuspended and such metals are taken-up by filter feeders. Sediments can reflect the quality of the water system and can be used to detect insoluble contaminants (Karthikeyan et al., 2007)
Heavy metals are conventionally defined as elements with metallic properties and an atomic number >20. Heavy metals concentrations in aquatic ecosystems are usually monitored by measuring their concentrations in water, sediments, and biota (Oguzie, 2003). Pollution by heavy metals is a serious problem due to their toxicity and ability to accumulate in the biota (Islam and Tanaka, 2004). Metal pollution has a harmful effect on biological systems and does not undergo biodegradation and accumulated in living organisms, thus causing various diseases and disorders even in relatively lower concentrations (Pehlivan et al., 2009). A substantial level of heavy metals causes the major hazard to the environment and accumulates in the ecosystem through two major paths; the first path
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From an environmental point of view, coastal zones can be considered as the geographic space of interaction between terrestrial and marine ecosystems that is of great importance for the survival of a large variety of plants, animals and marine species (Castro et al., 1999). Sediments act as the most important component of river ecosystem received the reservoir or sink of metals and other pollutants in the aquatic environment (Halcrow et al.,

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