Mahmood Hossain*
Forestry and Wood Technology Discipline, Khulna University, Khulna-9208, Bangladesh.
Md. Golam Rakkibu
Forestry and Wood Technology Discipline, Khulna University, Khulna-9208, Bangladesh.
Copper; Heavy metals; Pollution; Accumulation; Aquatic ecosystem
Forestry and Wood Technology Discipline, Khulna University
Risk Management in Agriculture
Sources of Copper as a Pollutant The majority of copper deposits are found around the Pacific rim and the mountain belts in southeastern Europe and central Asia. Areas in Australia and Siberia also contain relatively large deposits of copper. Estimate of Cu which has been emitted globally into the atmosphere from natural sources ranges from 10 to 18X103 tons annually and provide a general reference for the assessment of pollution. Man-influenced sources cause greater local impact and are quite significant globally (56X103 tons/year). The largest sources are windblown dust materials from bush-fires, volcanoes and plants exudates also contribute (Nriagu, 1990).
Batey et al. (1972) reported that excess copper in soil arises as a consequence of industrial or agricultural activities. Copper smelting and refining industries, manufacturers of copper products and sewage disposal processes all contributed to the man-made input of copper to the biosphere. Similarly, the use of copper based agrochemicals over extended periods could lead to excessive accumulations of soil copper in localized areas. The aquatic environment received additional copper through erosion of copper enriched soil as well as surface runoff water during rain.
The anthropogenic deposition of copper compounds into natural environment has increased steadily since the dawn of civilization. Much of the Cu pollution associated with industrial/urban activities is released from point sources from which dispersal is strongly dependant on local meteorological and topographical factors in relation to stack height and aerosol size (Tiller and Merry, 1981). At present industrial discharges of copper into the environment exceed natural fluxes by about 300%. The total flux of copper to the atmosphere is approximately 75,000 metric tons per year of which 5000-13,000 tons are deposited into the ocean. Atmospheric emissions are the main route of entry to the environment. Through processes of wet and dry deposition, atmospheric copper enters into the hydrological cycle either by deposition onto soil and subsequent erosion into water bodies or direct deposition into rivers, lakes and oceans (Nriagu, 1990).
Copper in Aquatic Ecosystems Copper in trace amounts is required by all living organisms. However, when present at concentrations higher than those required, it may become highly toxic. The normal concentration of copper in the open oceans and in river water ranged from 1-3 ppb (Goldberg, 1963) and 0.003 mg/L (Mullins, 1977) respectively. Depending on the sources of copper, its level both in coastal and river water varies widely throughout the world and high copper concentration in coastal areas can often be attributed to input from municipal wastes, industrial waste water and direct discharge of farm wastes to the aquatic environment.
The concentrations of copper sometimes encountered in coastal water and approach the incipient lethal concentrations for some marine animals (Calabrese, et al., 1973). Relatively little published information on the sublethal biological effects of copper on fresh water invertebrates, fish and plants, is available.
Effect of Copper on Aquatic Invertebrates The free cupric ion has been shown to be a dissolved species of copper which determine its toxicity to aquatic organisms (Seenda and Lewis, 1978). Copper is highly toxic to most fresh and marine invertebrates. Some species can adopt with high levels of copper and sensitivity is inversely related to the age and size of the organisms. Among invertebrates molluscs and malacostracan Crustacea seem to be the most susceptible than Oligochaeta with Diptera. Trichoptera and some other insects seem to be most resistant. Absorption of copper for marine invertebrates is found to be influenced with the variation of salinity in water bodies. Lang et al. (1981) has recorded more than 160 ppb copper concentration in Barnacle larvae (Balanus improvisea) at 30 ppt salinity at 150C temperature and 80 ppb concentration of copper at the 15 ppt salinity at the same temperature. The factors involved in the toxicity of heavy metal like copper is numerous and complicated and also depends on the form of metal in water. Factors influencing the physiology of an organism such as salinity and temperature also contribute to the toxicity of heavy metals.
Khulna University Studies, Vol. 1, Issue 2, December 1999, pp. 259-266
Journal