Distrubtion Of Two Typical Organic Pollutants In The Yangtze River Estuary And Toxicology Effects On Fish

The Yangtze River is the longest river in China and the third longest in the world.Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides wereimportant persistent organic pollutants. The aim of this study is to examineorganochlorine pesticides and low molecular weight polycyclic aromatichydrocarbons (LMW PAHs) distribution in water from the Yangtze River estuary andtry to develop a set of biomarkers to indicate PAHs and OCPs pollution level in thefollowrag study areas. The histopathologic and embryonic biomarkers of zebrafish(Brachydanio rerio) and Yellow cartfish (Pelteobagrus fulvidraco) were used toassess the toxicology of organochlorine pesticides and LMW PAHs in water andsediment of the Yangtze River estuary. The results of the present research areas asfollows:(1) The concentration and distribution of LMW PAHs, i.e., naphthalene,fluorene, phenanthrene and anthracene were monitored in November 2005, Marchand July 2006 in the water of the Yangtze River. The LMW PAHs in the aqueoussamples were extracted via C-18 solid phase extraction cartridges (SPE) andquantitatively determined by high performance liquid chromatography with ultraviolet detection and fluorescence detection (HPLC-DAD/FLD). Comparing withthose of other rivers in China, the mean concentration of PAHs in the Yangtze Riverwas of moderate level. The concentration of PAHs in the surface water of NT andXLJ were higher than other sites in the Yangtze River estuary. The individualcomposition of PAHs was characterized by naphthalene, and phenanthrene was thesecondary component in high flow season. However, the individual composition ofPAHs was characterized by phenanthrene, and naphthalene was the secondarycomponent in normal flow season. The ratios of phenanthrene to anthracenesuggested that PAHs in the water were derived from many sources in high flowseason and normal season. And PAHs were derived from combustion of fossil fuels inlow flow season. The seasonality of the mass concentration of PAHs was significant,and the level of PAHs in high flow season was higher than that in low flow seasonand normal season. (2) 7 kinds of organochlorine pesticides (OCPs, including HCHs and DDTs) inwater from the Yangtze River were determined by using solid phase microextraction(SPME)-gas chromatography with electron capture detector. Compared with otherrivers in China, the mass concentration of OCPs in the water of the Yangtze Riverwas of moderate and a bit higher level. However, the concentration in the sedimentwas of lower lever. HCHs had higher mass concentration than DDTs. Distributioncharacteristics of OCPs components showed there were some new input oflindane(γ-HCH) in near term at most sections. Mass concentration of OCPs in waterwas distinguishing at different season, which was higher in high flow season than inlow season and normal season. Agricultural runoff and soil denudation enhanced inhigh flow season, and took more OCPs into the Yangtze River.(3) Water pollution induces pathological changes in fish. As an indicator ofexposure to contaminants, histology represents a useful tool to assess the degree ofpollution, particularly for sublethal and chronic effects. In this papers,histopathological effects of lindane and phenanthrene on gill and liver of zebrafish(Brachydanio rerio) were determined by light microcope, respectively. The fish wereexposed to the different concentrations of lindane(0, 0.01, 1.0 and 100.0μg/L) andphenanthrene (0, 0.05 and 100.0μg/L) for 36 days. There were no pronouncedhistopathological alterations in gill and liver of fish exposed to 0.01μg/L lindane,which suggested there were no evident effect on gill and liver of fish of lindane levelin the Yangtze River estuary. The common gill alterations at 1.0 and 100.0μg/L lindanwere desquamation of epithelial cell, hypertrophy of epithelial cells and deformationof pillar cells. Exposed to 1.0 and 100.0μg/L lindane for 36d, hepatic lesions in liverwere characterized by hepatocyte hypertrophy, nuclear atrophy and deformation,vacuolization, focal necrosis and lipidosis. The histopathological changes in gill andliver tissues of Brachydanio rerio were sensitive to phenanthrene exposure. It hadalready had toxic action on gill and liver of fish exposured to 0.05μg/L phenanthrene,which suggested the toxic action of phenanthrene level in the Yangtze River estuaryon gill and liver of fish. In the gills epithelial hypertrophy and edema were observed,in the liver there were hypertrophy of hepatocytes and vacuolization. After exposureto 100.0μg/L phenanthrene for 36 days, the lesions in gill were characterized by thickening of the filament epithelium and lifting of the lamellar epithelium; In theliver the shape of hepatocytes were irregular, some nuclei were atrophy anddeformation or in a lateral position close to the cell membrane, hepatocytes werehighly vacuolated, and focal necrosis occurred after cytolysis and karyolysis.Impairments of gill and liver of fish increased with increasing concentrations ofchemicals. The histopathological effects on gill and liver of zebrafish could also beused as a biomarker and an early warning indicator of PAHs and lindane pollution.(4) The juvenile Yellow cartfish, Pelteobagrus fulvidraco, which was artificialpropagated in our laboratory, was exposed to phenanthrene at environment level inYangtze river (0.05μg/L)and sublethal concentration(100μg/L) for 0.25, 1, 3, 7,14days in experimental condition to investigate the effects on the main antioxidantenzymes: superoxide dismutase (SOD), catalase (CAT) and seleniumdependentglutathione peroxidase (GPX) in the liver of fish. The results showed that SOD andCAT and GPX content in the liver of Pelteobagrus fulvidraco were significantlyrelated to phenanthrene pollution level in water. After low concentration ofphenanthrene exposure, more superoxide radicals could be produced, and theactivities of hepatic SOD were significantly induced, and the generation of O₂^·- waswithin the SOD elimination capacity. Otherwise, with the concentration ofphenanthrene up to the certain extent, the O₂^·- generation increasing and exceeds thefunction of SOD elimination, the O₂^·- as well as other oxyradicals can inversely insultthe enzyme to make it inactivated. The GPX content in the liver of Pelteobagrusfulvidraco exposed to phenanthrene was principally induced, and CAT activities weresuppressed during early days. With the prolonged exposure, the antioxidant enzymesactivities were up to the control value. All the results showed that CAT activity in fishliver were more sensitive to phenanthrene exposure, therefore, they could also beused as a biomarker and an early warning indicator of phenanthrene pollution.(5) The embryo development technique in zebrafish, Brachydanio rerio, is atoxicity testing method making use of sensitivity of fish embryo development in earlystage to study and evaluate the specific effecting mechanism, the most sensitiveeffecting time, embryo toxicity and teratogenicity of chemicals through observing thedevelopment process of zebrafish embryo after chemicals exposure to fertilized ova. This technique was used to test toxicity of phenanthrene in this papers. The resultsshowed that phenanthrene could markedly inhibit the development of Brachydaniorerio embryos, and caused its malformation and even death. There were differenttoxicity endpoints which could be observed in embryos exposed to phenanthrene withdifferent time. And the most sensitive effect duration of phenanthrene was blastulastage The acute toxicological endpoint of Brachydanio rerio embryos was in order of96h hatching rate＞48h lethal rate＞24h coagulated eggs＞96h abnormalities. Theembryo development of zebrafish could also be used as a biomarker of PAHspollution.(6) The suitability of a sediment contact assay using zebrafish (Brachydaniorerio) embryos to evaluate the degree of sediment contamination in Yangtze Riverwas investigated in this papers. Fertilized zebrafish eggs were exposed to both thewhole and organic extract concentrations prepared from collected sediments from 6sites along Yangtze River (from Nanjing to Shanghai). The different toxicityendpoints, such as mortality, abnormality, heart rate, and hatching rate in thedeveloping embryos were recorded during a 96h exposure. The results showed thatthe embryotoxic of sediment in Yangtze river was NT, XLJ and ZY were moreseverer than SDK, NG and BG, and teratogenic responses in embryos exposed toorganic extracts were more severe than whole sediment exposure. Furthermore,embryotoxic responses by zebrafish embryos to sediment exposures were alsodiscussed in relation to the analyzed contaminants in the sediments (heavy metals,PAHs, DDT, HCH, solvent). Overall, the present study points out that the sedimentcontact assay with zebrafish embryos offers a practicable and highly sensitivebioassay for the general assessment of sediment toxicity of Yangtze River estuary.