The Toxic Effects Of Contaminated Water On Fish Species In Lanzhou Section Of The Yellow River

Large numbers of pollutants are discharged into the Yellow River in Lanzhou and Baiyin region every day, which makes the river polluted seriously. Inevitably, organisms including fish species are affected adversely, and health of residents relying on the river for water supply are threatened, either. It is very important to control of the water pollution. Whereas, evaluating water quality precisely is the premise of water pollution control. The toxic effects of polluted water on organisms could reflect the condition of water pollution, and it is helpful to make the risk assessment of polluted water for human being. Using fish to monitor water pollution would supplement the routine water monitoring.In this study, two dominant endemic fish species, Triplophysa pappenheimi and Gobio hwanghensis, both common in Lanzhou section of the Yellow River, were chosen as target species for evaluating the toxic effects of polluted water.First, the toxic organic pollutants in fish tissues were identified qualitatively and the concentrations of heavy metal (Cu, Pb, Zn and Cd) in fish tissues (liver, kidney, gill and muscle) were determined quantitatively.Second, the toxic effects of polluted water on fish were evaluated by determining the total anti-oxidant capacity (T-AOC) and the level of malondialdehyde (MDA), by statisticly analyzing of the micronucleus frequency (MCN), and the degree of DNA damage, and by the histological observation.Last, the evaluation of polluted condition in Lanzhou section of the Yellow River and risk assessment for human being were conducted based on the presence of toxic organic pollutants, the concentration of heavy metals in fish tissues, and the variation of fish oxidative stress markers (T-AOC and MDA), genetic material damage markers (MCN and DNA damage) and pathological observation. The results showed that:1. Qualitative analysis of organic pollutants:eight kinds of toxic organic pollutants in liver of T. pappenheimi were found by means of GC/MS, which were: Nitrobenzene, Carbon Tetrachloride,1,4-Dioxane, Toluene,2-Naphthalenamine, Tetradecane, Octadecane and Eicosane. These pollutants have been considered as carcinogen, suspected carcinogen or carcinogenic promoting agents. 2. Evaluation of heavy metal pollution in Lanzhou section of the Yellow River:Both in Lanzhou and Baiyin, Cu,Pb,Zn and Cd concentrations in water body met the third-class water quality standard restricted in Environmental quality standards for surface water (GB 3838-2002). In sediment they did not exceed the effects range-low values described by the National Oceanic and Atmospheric Administration of America.In fish muscles they did not exceed evaluation criteria limited in Safety qualification for agricultural product for non-environmental pollution aquatic products (GB 18406.4-2001), respectively.3. Comparison of heavy metal pollution between Lanzhou and Baiyin:In water body, Baiyin Cu, Pb, Zn and Cd concentrations were significantly (P<0.05) higher than those in Lanzhou, Pb concentration exceeded the maximum permitted level prescribed in Standards for Drinking Water Quality (GB 5749-2006). In sediment, Baiyin samples contained higher concentrations of Cu, Cd and lower concentrations of Pb than those in Lanzhou sediment (P<0.05). In G. hwanghensis tissues, Cu and Zn levels in fish obtained from Baiyin were similar to those from Lanzhou(P>0.05), Baiyin fish contained significant higher Cd and lower Pb concentrations than those in Lanzhou fish (P<0.05).4. Distribution patterns of heavy metal in fish tissues:heavy metal concentrations in inner organs were all higher than those in muscles. Cu and Pb were found highly accumulated in liver, Zn in gill and Cd in kidney.5. Toxic effects of polluted water on fish:T-AOC in liver, kidney and gill were significantly lower than that in the same tissue of control samples (P<0.05), while the MDA level, MCN frequency and DNA damage were all significantly higher than that in the same tissue of control samples (P<0.05). Obvious pathological changes in liver, kidney, gill and intestines were not observed.In conclusion, the presence of carcinogen, suspected carcinogen or carcinogenic promoting agents in fish tissues indicated that the polluted water in Lanzhou section of the Yellow River may bring cancer risks to organisms including human being. Lanzhou section of the Yellow River was not significantly contaminated by Cu, Pb, Zn, and Cd. Pb in Baiyin section may bring health risk to human being if it is used directly as drinking water. The accumulation of pollutants in fish tissues had caused oxidative stress and genetic material damage, but had not yet injured fish tissues. Heavy metals accumulated highly in liver and kidney of T. pappenheimi and G. hwanghensis. As a result, liver and kidney had potential value on monitoring metal pollution. T-AOC, MDA, DNA damage or MCN in tissues (liver, kidney, gill or peripheral blood) of T. pappenheimi were all useful bio-indicators in monitoring water pollution.