Studies On The Characteristics Of The Distributtion And Accumulation Of Benzo(a) Pyrene And Cadmium In Subcellular Fractions Of Eisenia Fetida

Heavy metals and polycyclic aromatic hydrocarbons(PAHs)are typical pollutants usually co-exist in soils.Among them,Benzo(a)pyrene(BaP)and Cadmium(Cd)pollution are the representative pollutants due to their great toxicity and high occurrence.With the different physicochemical properties,their environmental behaviors and toxic effects are not same,and these might influence the pathways to be ingested by the organisms.Also the distribution and accumulation of the Cd and BaP in the organisms might be affected.Earthworms,which play an important role in soil health and their key position in terrestrial food chains,were chosen as the bio-indicator organisms for ecological risk assessment,especially for the Eisenia fetida.Therefore,single and combined pollutions of Cd or BaP were set to examine their subcellular distribution in the earthworms,meanwhile,the mechanism of the accumulation of these typical pollutant were also explored.The results are showed as follow:1.The distribution and accumulation of pollutant in earthworms at the subcellular level were heterogeneity and were influenced by the types of pollutants.Cd mainly accumulated in Fraction C(associated with cytosol),and followed by the Fractions D(associated with granules)and Fraction E(associated with tissue fragments and cell membranes).While BaP mainly accumulated in Fraction E(associated with tissue fragments and cell membranes)and followed by the Fraction D(associated with granules)and Fraction C(associated with cytosol).2.The BaP accumulation in sucellular fractions were stimulated by the addition of Ca2+ in different concentrations.The accumulation of BaP increased firstly and then decreased with the increasing Ca2+concentration.According to the RDA(Redundancy analysis),BaP concentration was significantly related with the protein content and AChEactivity in Fraction D,and it was significantly related with the protein content in Fraction E.Therefore,the BaP accumulation was influenced by the Ca2+ which might by influencing the expression of protein and the activity of AChE.3.For the combined pollution,the single BaP concentration and different Cd concentrations were mixed.The BaP accumulation in subcellular fractions were significantly inhibited with the addition of Cd in different concentrations.Correlation analysis showed that BaP accumulation was negatively correlated with the protein content and AChE activity in Fraction C,and negatively correlated with the protein content in Fraction E.This might because that Cd could compete with BaP for binding with protein,or stimulated the expression of AChE so that improved the defense ability and metabolism effect to the exogenous pollutants,which then decrease the BaP accumulation.With the addition of BaP,the accumulation of Cd in subcellular fractions were significantly inhibited under the high Cd concentration treatment.According to the RDA,the Cd concentration was closely related with the protein content and AChE or GST activity in Fraction D,and it was closely related with the protein content in Fraction E,while it was closely related with the GST activity in Fraction C.So the BaP might influence the synthesis of protein or the activity of some detoxification enzymes involved in exogenous pollutants metabolization,such as AChE and GST,and then influence the accumulation of Cd.The accumulation of the BaP and Cd were reduced under the combined pollution of BaP and Cd compared to the their single exposures,i.e.an antagonism effect exist between BaP and Cd..4.Study the effects of different concentrations or single concentration of blockers on the accumulation of BaP under the single pollution or combined pollution of BaP and Cd.The results showed that,the Ca-channel blocker(Lanthanum,LaC13)could stimulated the accumulation of BaP in subcellular fractions whether in single pollution or combined pollution,and the SH blocker(Nitrogen-ethylmaleimide,NEM)also stimulated the accumulation of BaP in subcellular fractions except in Fraction C under the combined pollution.And the BaP accumulation in Fraction E under the combined pollution were lower than that under the single pollution.