Environmental Contaminants

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1. GENERAL INTRODUCTION
The environment is continuously loaded with foreign chemicals (xenobiotics) released by urban communities and industries. A wide range of natural, pharmaceutical and synthetic chemicals released into the environment are estrogenic (Purdom et al., 1994). The chemicals enter into aquatic ecosystems through both point and non – point. The point chemicals are sewage treatment, pulp mill and industrial effluent and the non-point are urban and agricultural runoff. The stream contains excessive amount of a specific pollutant or non-pollutants. The materials which cause pollution include inorganic salts, acids, alkalis, suspended solids, toxic metals and metalloids. In order to ensure the sustainable use of marine ecosystems,
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There is on-going regulatory and research concern for metals in the environment and numerous regulations have been implemented globally to control or curtail natural and anthropogenic industrial metal emissions. Contaminants are the substance that can endanger the environment, humans, animals, plants, soil or water (Hoffmann, 1998). Human impact on the environment or anthropogenic impact on the environment includes impacts on biophysical environments, biodiversity and other resources (Sahney et al 2010; David and Alan 2008). The term anthropogenic designates an effect or object resulting from human activity. The atmospheric scientist Paul Crutzen introduced the term "anthropocene" in the mid-1970s (Crutzen et al 2000). The term is sometimes used in the context of pollution emissions that are produced as a result of human activities but applies broadly to all major human impacts on the environment (Scott 2008).The sources of the contaminant provide pathways for the release of not only organic contaminants but also heavy metals, which can be highly toxic in very small quantities (Memon et al., 2001; Memon and Schroder, 2009). The study of metals in the marine environment has received considerable attention because of their biological significance as well as the possibility of their transfer to man…show more content…
The near-surface flow speed is typically related to the river discharge and, for the sake of argument, on the order of 0.1 m/s. The depth-averaged flow Uf is typically very small, tending to zero, in estuaries of vigorous water exchange because there will be as much net outflow as net inflow. In estuaries with weak net inflow, such as well-mixed and salt-wedge systems, the depth-averaged flow will be similar in magnitude to the surface outflow. Therefore, the circulation parameter is >10 in estuaries with vigorous gravitational circulation and close to 1 in estuaries with unidirectional net outflow. In general, the greater the circulation parameter, the stronger the gravitational circulation (Cameron and Pritchard,
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