Pollution Of Heavy Metal In Freshwater Fish And The Correlation Analysis On The Environment

As one of the major aquatic products for daily consumption,the freshwater fish is extremely important in fishery economy and residents’ life.However, with increasingly prominent heavy metal pollution in aquatic environment, heavy metal pollution in fish has attracted much attention and effected the edible safety of freshwater fish. At present,the majority research areas of heavy metal pollution in fish were concentrated on the enrichment differences in the same organs of different fish species,as well as the enrichment differences in different organs of the same fish species and the enrichments differences of different living environments. The researches rarely involved influence factors such as growth period, life style of fish and related environmental factors. Therefore, this article made comprehensive in-depth analysis and researches on heavy metal pollution in freshwater fish with the concerns of these influence factors.The research samples of freshwater fish were collected at the east Dongting Lake and fish farms in Changsha City. The research contents including:1)Heavy metal accumulative regularity in different organizations, different species and different sampling site in three fish species (grass carp,carp and catfish) from the East Dongting Lake;2)Enrichment of heavy Metals in growth period of cage cultured carp (cyprinus carpio) from the East Dongting Lake;3)The correlation analysis between heavy accumulation in tilapia from fish farms and environmental factors including water,sediment and feed;4) Heavy metals accumulative difference and the evaluation of the heavy metals pollution in grass carp by different pattern of life. These study consequent provide certain reference data for food safety,freshwater fisheries aquaculture and environmental management.This experiment was divided into sampling in field and testing in the laboratory. Wild fishes and cage cultured carp from the East Dongting area were collected on February to July2012. Cultured tipalia from fish farms in Changsha City were collected on September2012. All fish samples were washed and dissected firstly, and the detection methods refered to national standard GB/T5009series. Laboratory data was analyzed by SPSS11.7.The results showed:1) Except Zn in the gills,Pb,Cd,Cu and Cr in the kidney or the liver reached the maximum concentrations, while the concentrations reached the lowest levels in muscle. The species,growth period and life style of fish have no effect on heavy metal accumulative regularity in different tissue.The heavy metal concentrations varied with fish species, while carnivorous and omnivorous species shared relatively higher concentrations than phytophagy species, showing some kind of biomagnification. Moreover,heavy metal contents in fishes from different sampling sites showed certain difference and fishes from sampling sites with more severe heavy metal pollution showed higher heavy metal concentration.2) In aquatic environment of cage cultured carp, the water quality belonged to level I according to the "Environmental Quality Standards for Surface Water"(GB3838-2002). The concentration of heavy metals in the fodder was relatively higher, which made the fodder become the main possible source of heavy metals pollution in carp. The w(Pb) and w(Cu) increased with the fish growth, while the w(Zn) and w(Cd) increased firstly and decreased later.3) In aquatic environment of cultured tipalia, the contents of heavy metals in water and feed was lower than maximum levels in relevant standard excepting for w(Zn) and w(Cu) in feed,which were higher than the recommended values in formula feed for tilapia. The ERri and RI of heavy metals in sediment indicated a mild polluting level on the basis of the Hakanson potential ecological risk analysis. Arccording to correlation analysis, heavy metals in sediment and feed showed significant correlation with the heavy metal contents in gills and muscle, while water showed little effect on heavy metal accumulation in tilapia. Meanwhile, heavy metal concentrations in the muscle and gills showed significant correlation while heavy metal in sediment and feed had an obvious correlation.4) The heavy metals concentrations in cultured grass carp were much higher than in the wild grass carp, which means a much higher pollution extent in cultured grass carp.The water and food in the living environment had a close relationship with the heavy metals pollutions,while strict management was necessary.