Ecotoxicological Effects And Different Mechanisms Of Heavy Metal And Organic Pollutants On Earthworm(Eisenia Fetida)

Soil is an important part of the environment,It is estimated that more than 90%of the total burden of pollutants resides in the surface soils.Heavy metals and organic pollutants are frequently found together as contaminants in soils and have attracted much attention in recent decades.However,they are mostly concentrated on the effect of a single organic pollutants and heavy metals.In fact,contaminated soils usually contain mixtures rather than a pure substance in the real environment.It is very important to investigate the compound pollution between heavy metal and organic pollutant for the management and diagnosis of soil pollution.Earthworms(Eisenia foetida)is the representative organisms in soil animals,which have become a bioindicator of soil contamination.Therefore the acute tests of heavy metals(cadmium)and organic pollutants(benzoapyrene and polychlorinated biphenyls)to earthworms was performed in this study in order to know the toxicity and mechanism of toxicosis of these typical heavy metal and typical organic pollutant on environmental organisms.On this basis,the effects of cadmium and benzoapyrene single and combined pollution on earthworms contaminant distribution and molecular response mechanisms to the ecological risk of organic pollutants and heavy metals under single and combined pollution conditions to provide a scientific basis and practical guidance.The results are showed as follow:1.Cadmium,benzo[a]pyrene and polychlorinated biphenyls contamination can inhibit the growth of earthworms,caused effect of oxidative stress,lead to DNA damage.DNA damage was the most sensitive parameter.detailed result:(1)Cadmium can cause superoxide dismutase activity increased,while inhibiting the enzyme of catalase and peroxidase earthworm activity.At high concentrations,malondialdehyde content significantly increased.The soil type and the duration of cadmium exposure significantly influenced the percentage of weight variation,DNA damage and antioxidant enzymesactivity.(2)Benzoapyrene can cause a significant increased in earthworm catalase activity,superoxide dismutase activity increased first and then decreased,peroxidase activity increased only in low concentrations,and at high concentrations the malondialdehyde in earthworm significantly increased.The soil type and the duration of cadmium exposure significantly influenced the percentage of weight variation,DNA damage,catalase activity and superoxide dismutase activity.In addition,the duration of cadmium exposure significantly influenced the peroxidase activity.(3)Polychlorinated biphenyls caused earthworm antioxidant enzyme activity increased with increasing concentrations,and the malondialdehyde content decreased slightly.The soil type and the duration of cadmium exposure significantly influenced the percentage of weight variation,DNA damage,catalase activity and superoxide dismutase activity.In addition,the duration of cadmium exposure significantly influenced the peroxidase activity and malondialdehyde content.2.The distribution of pollutant,a dynamic process,in earthworm is heterogeneity and it nfluenced by the exposure time and exposure concentration.Moreover the types of pollutants can also affect the distribution of contaminants in the earthworm:(1)at tissue level,the concentration of cadmium appeared bodywall,the concentration of benzo[a]pyrene appeared at body fluid and gut.When combined pollution,only 14 days of high pollution concentrations composite group,the content of cadmium and benzo[a]pyrene appear decreased,other treatments were not.(2)at subcellular level,the concentration of cadmium appeared followed fraction C(associated with cytosol)>fraction E(associated with tissue fragments and cell membranes)>fractions D(associated with granules).The concentration of benzo[a]pyrene appeared followed fraction E>fractions D>fraction C.For joint pollution,the concentration of cadmium were no significant change at fraction E and fractions D,and elevated at fraction C.The concentration of benzo[a]pyrene were no significant change at fraction C,fraction E and fractions D.(3)at sub-organism level,the concentration of cadmium and benzo[a]pyrene appeared post-clitellum.For joint pollution,the concentration of cadmium and benzo[a]pyrene at post-clitellum were significant reduced after 14d exposed.3.The single or complex pollutant contaminants could effect the concentrations in earthworm,enzyme activity and gene expression.(1)the concentration of pollutants in errathworm were increased with the increasing concentration of soil.Compared with the single contaminant,concentrations of contaminants in earthworms increased at middle concentrationgroup and reduced at high concentrationgroup.(2)the catalase activity,superoxide dismutase activity and gene expression levels increased with increasing concentrations of cadmium,catalase activity and gene expression does not changed with the concentration of benzo[a]pyrene.The superoxide dismutase activity and gene expression in the low concentration group increased and didn't change in middle concentration or high concentration group.When combined pollution,the synergistic effects occurred at middle concentration group and antagonism occurred at high concentration group.The peroxidase activity elevated only at high concentrations.The malondialdehyde content was significantly higher in the high-concentration group.Under the combined pollution,earthworms group malondialdehyde content was significantly increased at middle concentration group,and declinedat high concentration group.(3)the metallothionein gene expression is mainly affected by cadmium concentrations,and increased only at combined pollution of middle concentration group.heat shock protein 70 gene expression affected by the concentration of cadmium and benzo[a]pyrene,and reducedatcombined pollution ofhigh concentrations group.Translationally controlled tumour protein gene expression affected by benzo[a]pyrene concentration,translationally controlled tumour protein gene expression level increased at combined pollution of middle concentration group,and reduced at combined pollution ofhigh concentrationsgroup.