Bioaccumulation of Zinc in Fresh Water Fish Channa Punctatus Exposed to Mixture of Pollutants

Introduction

Among various toxic pollutants, heavy Metals are especially severe due to trend of bio-magnification in the food chain. Global heavy metal pollution of water is a major environmental problem with the advent of Agricultural and Industrial Revolution; Most Water Sources are getting contaminated. Poisonous and containing industrial discharges Hazardous substances including heavy metals. Our health and environment have become almost synonymous today; it is equally true for all biotic organisms, and fishes are thus no exception. Fishes are one of the most primitive groups of vertebrates and their environment i.e. hydrosphere is everything for them. The impairment of behavioral and physiological functioning due to polluted ambient habitat could result in gradual reduction in the adaptation capacity of a species leading to decrease in the survival capacity and gradual fall in population density.

Chemical mixtures are characteristic of life. The environment, including soil, air, food and all kinds of living organisms is a complex mixture of chemicals. The nature of the mixtures varies widely according to the specific chemical present and their concentration with in living system, which is controlled within relatively close limits. Furthermore, as is well known to toxicologists, all chemicals, both natural and synthetic are capable of producing adverse effects under some exposure conditions. Fortunately, individual chemicals differ widely in their capacity to produce adverse effects. Indeed for many individual elements and chemical compounds, there is a spectrum of effects associated with exposure. In some cases the elements or chemicals may be essential for life, delicately balanced between deficiency, sufficiency and toxicity with increase in levels of intake.

Contamination of soil and water is caused often by chemical mixtures than by single pollutants. Common examples of mixed chemical pollutants include gasoline; crude oil and land fill leachates. Although these mixtures consist essentially of organic compounds, other pollutant mixtures may include both organic and inorganic chemicals such as B heavy metals. Even in cases where a site is contaminated by only one pollutant, the generation of degradation products, such as humic acid changes the chemical makeup of the soil and water at the site so that they are better described as mixtures. Therefore, the toxicity of mixtures or combinations acquires great significance. Zinc is widely used in semiconductors, solar panel devices [1], paints, personal care products (sunscreens) and even in waste water treatment. Although, zinc is an essential trace element for both plants and animals but it induces toxicity at elevated concentrations particularly under conditions of low pH, low alkalinity, low dissolved oxygen and elevated temperatures [2]. Partially but relatively quickly, zinc dissolves in water, and releases free zinc ions which become primary source of aquatic toxicity [3, 4, 5]. Moreover, in combined state (ZnO) higher toxicity of zinc has been reported [6, 7, 8, 9, 10], than dissolved Zn (II) alone. Zinc is the only metal to be involved in all six classes of enzymes viz; oxido-reductases, transferases, hydrolases, yases, isomerases and ligases [11]. Greig, et al. studied the concentration of silver, cadmium, copper and lead in liver of windowpane flounder and reported values which were typical for finfish. Stromberg, et al. studied pathology of lethal and sublethal exposure of fathead minnow to cadmium. The radiotracer studies using cadmium`’`’ showed a rapid uptake and two phase elimination of cadmium by the fish. This rapid elimination correlated with lesions in urinary epithelium. Ueda, et al. studied accumulation of cobalt by marine fish Chromium is reported to be toxic at higher concentrations and causes histopathological and ultrastructural changes in several tissues of aquatic animals [12, 13, 14]. Mohammad, et al, determined the distribution of heavy metals in the water and sediments collected from Kali Nadi, U.P. and their accumulation was also recorded in the fresh water fishes, Kuroshima, et al. studied accumulation of cadmium in the mummichog Fundulus heteroclitus adapted to various salinities. Abu, et al. reported the concentration of mercury, cadmium, copper and zinc in two populations of Fundulus heteroclitus. One population was from piles creek (PC), a polluted tidal creek in a heavily industrialized area in Linden, New Jersey, and the other population was a pristine area in Southampton, long Island (LI), New York. Copper is an essential element and tends to accumulate to a greater extent than other essential elements, such as zinc and iron [15, 16]. Kargin, et al. reported accumulation of iron, zinc, copper, lead and cadmium in freshwater fish Capoeta barroisi tissues.

Discussion

In the present study it has been observed that the interaction between one metal with another metal can be antagonistic or synergistic. In some cases no interaction among them was noticed. Experiments on fish have shown that some effects of metals may be prevented by the simultaneous administration of other metals .In the present study groups of fishes exposed for 96 hr to zinc+cadmium, zinc+copper, zinc+endosulfan, zinc+cadmiuml-copper+endosulfan and Zinc+cadmium+copper+dimethoate the metal concentration decreased as compared to fishes exposed to zinc alone. Our results are supported by the findings of Moreau, et al. who reported that radioactive zinc and phenantherene at concentration approximately 50% of the 96 hr LC50 level demonstrated that phenanthrene caused a reduction in the short term accumulation of zinc by sheepshead fry. It is not clear, what mechanism would be responsible for the reduction of zinc accumulation, while it has been shown that similar interactions among aquatic diatoms species were due to competetions for binding to and uptake by the manganese uptake system [17].

Conclusion

In the present study it was concluded that concentration of zinc decreased when the fish were exposed to zinc+cadmium combination. Results clearly show that the level of accumulation of zinc in different tissues in the two types of exposure (individual and group exposure) varied. The level of accumulation was different in individual exposure because each fish had different physiological activity. Bioaccumulation of Zinc in both the exposure (individual and group exposure) was in order Gills>Blood>Kidney >Liver>Muscle.