Major Sources Of Water Pollution Nowadays
This globe is unique in its hospitality for living beings by providing varied kinds of life support systems. Nature integrated these in a dynamic equilibrium in which flora and fauna as well as higher forms of life could flourish, each taking its place in the intricate food chain. The interaction of man with physical, biological and cultural environments began millions of years ago through biological evolution. It has continued its development primarily through cultural evolution. It is the very inertia of this cultural evolution, which appears to lack certain necessary controls, that had led to the pollution problem. Pollution is perhaps the most dreaded word in the modern civilization. Literary meaning of pollution is “to destroy the purity or sanctity of something”, in the present context the most precious part of human life i. e. environment. Pollution now embraces all facets of environment viz. , air, soil and water. In the recent great impetus has been given to the industrial development, which has resulted in generation of pollutants in large quantities. Often such pollutants are having varied chemical properties. Besides, with growing human population, problems of domestic wastes are becoming grave and deteriorating the overall health of environment. As consequence most of our water bodies have become polluted due to increasing industrialization urbanization and other development activities. Although water is a dominant feature of earth but in fact we are left with only 0. 124 percent of total earth, s water which is present in rivers, streams, lake, ponds and such subsurface reserves. The total available freshwater is about 13×106 cubic kilometers. In india it is estimated that about 37×1011cubic meters of water falls in the form of rains.
Out of this water nearly 35 percent is evaporated from the surface and 40 percent flows down to the sea as natural drainage and only 25 percent get stored in the form of surface and subsurface waters. 70 percent of this available freshwater is 2 already polluted by wide spread disposal of urban and industrial wastes. At global level also "protection of freshwater resources" has been among the vital issues discussed by the heads from 160 countries during united Nations conference on Environment and Development held at Rio-de-janerio, Brazil in june, 1992, water is said to be polluted when it is changed in its quality or composition directly as a result of waste disposal and other human activities so that it becomes less suitable or harmful for drinking, domestic, agricultural, recreational, fisheries or other purposes. As per "water pollution " means such contamination of water or such alteration of the physical, chemical or biological properties of water or such discharge of any other liquid, gaseous or solid substance into water (whether directly or indirectly) as may or is likely to create a nuisance or render such water harmful or injurious to public health or safety or to domestic, commercial, industrial, agricultural or other legitimate uses or to the life and health of animals or plants or of aquatic organisms. Reportedly large quantities of pollutants are currently being released in to lentic and lotic waterbodies. These pollutants may be classified as biodegradable and non biodegradable pollutants, former are oxygen demanding wastes originated from human, animal and plant sources whereas later ones also known as persistant pollutants are perhaps the worst possible kind of pollutants since these cannot be destroyed or decomposed biologically over very long period of time among the naturally occuring and the industrial pollutants, heavy metals are worst offenders or toxic pollutants. They contaminate air, water, soil and enter food chains, posing serious health problems to human beings.
Heavy metal may be defined as a metal precipitable in acid solution by hydrogen sulphide. But a universally acceptable definition has been given by Passow (1961), Who defined the heavy metal as having a density greater than five. These metals range from twenty two to ninety in their atomic numbers. There are about thirty eight elements referred as heavy metals showing specifically high electric and thermal conductivity. Trace amount of certain essential metals are required for 3 survival, growth, reproduction and development of organisms. However, some metals are toxic even at low concentration and in excessive quantities all heavy metals cause harmful effects to organisms which may eventually lead to their death. The seriousness and persistence of heavy metal salts in water are compounded by the fact that they are generally water soluble, nondegradable and strongly bounded to polypeptids and protein of organisms (Jhingran, 1985).
Metal often acts as a bridge between the substrate and the protein, which can activate the metal by with drawing electron from it. All heavy metals share the common property of forming stable coordination complexes with macromolecules present in cell. This may result into inaction or inhibition of certain enzymes. Heavy metal bring considerable decrease in the rate of all metabolic processes of the cell including nulic acid synthesis, cell division and protein synthesis (Wickliff et al;1980 and Seigel, 1974). Industrial effluents and agricultural run-off burden the aquatic ecosystem with mixtures of toxic or potentially toxic metals. Many of these metals, having specific structures and properties, remain in the environment for prolonged periods and continue to pose health risks and environmental problems. Besides, metallic ions also enter the aquatic ecosystem mainly through mining industries, ore processing and metal work. These metals alter the chemical nature of the ecosystem, thereby affecting biota at all its stages i. e. , individuals, population and communities. The persistent accumulation in environment and effects (singular, additive or synergistics) of these chemicals in the biosphere are of prime consideration in the control of pollution. Since there is a constant release of trace elements in higher concentrations and often in unusual physico-chemical state, the fear of their being hazardous to fish health is now an undisputed truth. In order to assess adequately the impact of heavy metals on environment, it is important to consider that they may occur simultaneously in the environment, where they may interact to alter their individual toxicitites on living system. These 4 metals are harmful to all components of the community by their extreme toxicity. Considering the persistence and toxic nature of heavy metals, knowledge on their toxicity is important in evaluating safe concentrations for aquatic organisms. The discharge of these elements into natural water poses serious pollution problems and consequently affects the flora and fauna. To predict the ecological impact of heavy metals, various kinds of organisms have been recommended among which fishes are widely considered as suitable for bioassays. The heavy metals are usually present in aquatic habitat at very low concentration but as a result of the discharge of untreated effluents (from various industries) into the aquatic system results in subsequent increase in the concentrations of theses metals.
In recent years the concentration of heavy metals has Increased in all the aquatic biota due to continual discharge of the affluents containing heavy metals. Aquatic animals including fishes living in such environment will not only accumulate them but their anatomy, physiology, and behaviour also get affected. According to Sand bank and Nupen (1984) the most important problem of aquaculture in domestic effluent is the accumulation of metals, pathogens and pesticides in fish. These noxious substances may often get accumulated in food chain causing toxicity to fishes and may occasionally lead to human fatality. The persistence of heavy metals in water may be due to several factors such as solubility, bottom sediment, organic matter, temperature and pH. Some aquatic organisms are known to have higher levels of metals due to bioaccumulation.
According to Ahmed (1991) freshwater fishes are useful as bio- indicators of heavy metal pollution, because they act as collectors of harmful residues therefore these fishes should be considered useful tool for toxicity studies. The heavy metals are characterised by their special properties of having a higher electrical and thermal conductivity, ductility, opacity and reflectivity attributed to its free electrons and malleability. The heavy metals have a density greater than five. Their common feature in relation to biological life is that in excessive quantities they are poisonous and cause death to most of the living organism Silver, mercury, lead, cadmium, zinc, aluminium, nickel and chromium have been classed as metals of relatively high toxicity to fish. Some of the metallic pollutants of recent concern are copper, zinc, cadmium, Lead and mercury. These metallic ions are often constituents of raw materials and complex organic compounds for example, copper in zinc and phosphate mines. Salts of the most toxic metals, particularly silver, mercury and copper have been reliably reported harmful to fish in some freshwaters at concentration near 0. 01 ppm of metal. Zinc, a bluish white and relatively soft metals is very common aquatic contaminant in our country which is highly toxic to man and other aquatic organisms. Fishes are highly susceptible to zinc and copper toxicities. Relatively minute concentration of these metals in freshwater can be rapidly fatal when there has been virtually no absorption of metal, but only superficial accumulation.
Many heavy metals like Zn, Lead, Cadmium and copper are prime elements, which form major constituents of element in Southern Rajasthan. Rajasthan is famous 6 for its mineral resources in India. Over fifty different minerals are found in the state, out of which 35 are being mined. Major mineral based industries are Zinc smelting. These mineral based industries are also support ancillary and subsidiary industry in nearby area. Mineral wealth of Rajasthan has a pivotal role in the state and national economic development. These mineral based industries also support ancillary and subsidiary industries in nearby area. These industrial units are supposed to cause heavy metal pollution affecting the aquatic life in their surrounding waters. Therefore, for the past few years investigations on several parameters of toxicity of heavy metals such as zinc, copper, nickel, cadmium and mercury are being carried out by the department of Limnology and Fisheries.
The purpose of such investigations was mainly to examine the acute toxicity levels of these metallic ions using fish as a test organisms. From longterm safety point of view LC50 values determined by acute toxicity tests are of not much importance, because these values are merely convenient reference points for determining the safe concentration. Obviously, the safe concentration permitting normal life processes of animals is always much lower than LC50 values. The chronic toxicity study, which involves prolonged exposure of the experimental animals to toxic environments on the contrary can provide the safe concentration level, which is more significant and important to the environmental safety. Toxicity tests are necessary in water pollution, evalutions because chemical and physical tests alone are not sufficient to assess potential effects on aquatic biota. Pickering (1974) suggested that the estimation of water quality criteria for protection of all life stages of aquatic organisms should be derived from chronic toxicity.
Pollution is a by product of the modern age of industrialization and urbanization. This problem is attracting attention of scientists, administrators and social workers. Considering this, the present study has planned to investigate the effect of zinc effluents on the aquatic environment with special reference to flora and fauna. Including the bioaccumulation of heavy metals in organisms has also been studied. In the present investigation acute and chronic toxicity have been made to assess effect of Zinc on freshwater animals. Animals have been selected on the basis of ecological criteria and thus all types of habitat and niche are being represented in this selection. These animals were also exposed to effluent discharged by Zinc smelter Chanderiya which contains different metals, acting synergistically or antagonistically on freshwater animals. Present study is also aimed at assessing bioaccumulation during bioassay and biomagnifications of Zinc in animals inhabiting Berach river system study is further extended to know Zinc content in water, sediment, plants and animals in different water bodies of Berach river System to compare metal content of polluted and unpolluted Zones. Limnological studies have been also made in these water bodies to assess impact of Zinc stress on quality of water, species diversity of plankton, benthos and these along with primary productivity of these waters.
