Assessment of the concentrations of various elements in the surface water and sediment at four stations in the littoral zone of the eutrophic Hussainsagar Lake in the twin cities of Hyderabad and Secunderabad, indicated heavy metal pollution of both surface water and sediment of the lake. It was confirmed that of all the elements, the mean concentrations of Calcium (Ca) and Selenium (Se), and Mercury (Hg) among the heavy metals were higher in the surface water. The study further revealed abnormal concentration of the toxic heavy metalsCadmium (Cd), Hg, Chromium (Cr), Lead (Pb), Copper (Cu), Zinc (Zn) and Cobalt (Co) in the sediment. The concentration of most of the elements in the sediment was typically and significantly several folds higher than that of the surface water. Besides, the concentration of many of these elements was significantly higher at Station-IV that directly received inflow of municipal raw sewage along with industrial effluents from different catchments of the twin cities.

Elements including various metals form an integral part of the environment comprising its biotic component. Some of these elements play basic role in the organisms and are known as `essential elements' (Hughes, 1985). These elements are released into the environment significantly by various anthropogenic activities. The concentration and contamination of elements in the surface water and sediment of lakes and reservoirs of both nearby and remote watersheds are related to several factors, particularly atmospheric dry and wet depositions, and the conditions in the catchment areas and that of the aquatic ecosystems (Forstner and Wittman, 1983). Each element has a particular anthropogenic source inventory, for example, Mercury (Hg) from incineration of waste of both medical and municipal origin, and coal combustion; Arsenic (As) from industrial activities; Cadmium (Cd) from waste incineration; Lead (Pb) from traffic and waste incineration; and Selenium (Se) from coal combustion (Berdowski et al., 1997; and Ondov et al., 1996). The elements are strongly retained in the watersheds and are slowly released to aquatic environment (Mason et al., 2000), in which trace elements are scavenged by particles and deposited at the bottomsediments of the lake. Besides, these elements have also some autochthonous source, being introduced into the ecosystem through the weathering of parent rocks.

Some of these elements are bioaccumulated within the aquatic food chains and are potentially toxic to animals at higher trophic levels (Mason and Sullivan, 1997), including human beings, and produce both chronic and acute ailments (Forstner and Wittman, 1983; and Mason et al., 2000). Metal contamination in aquatic environment is an important global health concern. It has been recently shown that fishes of many freshwater lakes in Asia, Europe and North and South America contained elevated concentrations of metals particularly Hg, with concentration exceeding the national and international permissible limits (Mason and Sullivan, 1997).

Environmental Sciences Journal, Heavy Metals, Aquatic Environment, Biogeochemical Systems, Anthropogenic Sources, Anthropogenic Inputs, Combustion Processes, Toxic Heavy Elements, Metal Contamination, Coal Combustion, Aquatic Ecosystems.