Study On Ecotoxocological Effects Of Single And Combined Cadmium And 2,4-dinitrotoluene In Soil To Earthworms

Many soils are polluted with mixtures of moderate levels of contaminants.In China,the immense and sustained growth since 1970s has resulted in increased soil pollution.However,it remains unclear to what extent local ecosystems are endangered.This research reports on the single and combined pollution of Cadmium and 2,4-Dinitrotoluene(2,4-DNT)on earthworms Eisenia fetida in Beijing fluvo aquic soil for a serie of 4,7,11,14,21,30 days.The activity of SOD,CAT and GPX,which was significantly changed within the pollutant concentration range(P<0,05).The results showed that the high 2,4-DNT-50mg/kg concentration compared to Cd 10mg/kg could significantly(P<0.05)induce the antioxidant enzymes activities in earthworms because of the high oxidative attack.For the effect of aging time on the biological effectiveness of combined pollution in Beijing fluvo aquic soil,slightly biological changes in earthworms were observed within 123 days of the aging time process,earthworms showed rapid changes in SOD activity in the first 11 days and decreased slowly from day 11 to day 123 whereas CAT and GPx increases slightly during the 123days of experience.As the time increased Earthworms have demonstrated a strong tolerance for Cd combined to 2,4-DNT pollution.This was highly attributed to the one of the most important heavy-metal-inducible proteins metallothionein-2 expressed by earthworms,which is related to metal concentrations and the exposure times.Finally to analyze the influence of soil properties on Cd combined pollution to Earthworm Eisenia fetida.We selected Beijing fluvo aquic soil,Heilongjiang black soil and Jiangxi red soil for a series of 4,7,11,14,21,30 days.We observed different biological effectiveness from the combined Cd pollution in each soil type during our experiment.This was highly attributed to different soil properties in different soil types.Path analysis was used to decompose the correlations effects of different soil parameters with the path coefficients K_f,which define the sorption and adsorption of pollutants in the soil.According to the path coefficients,the sequence of direct effects to Kf is pH>Clay>CEC.Both zero-order correlation and path analysis show pH content has a significant positive effect on K_f,and the direct effect on K_f is much higher than CEC and Clay factors(path coefficient 1.214).Clay content is also in a very strong and positive correlation with the coefficient Kf because the clay particles are small in size;they facilitate a strong adsorption capacity of pollutants in the soil.The bioassay test on growth,reproduction and mortality in the earthworm species Eisenia fetida were executed in all soils,and a population model was used to assess the population level changes in growth reproduction and mortality.In Beijing fluvo aquic soil and loessal red soil,changes in biological effectiveness of earthworms Eisenia fetida were much higher compared to black soil.