Accumulation And Ecotoxicities Of 1,3,6,8-tetrabromocarbazole In Earthworms(Eisenia Foetida)from Spiked Artificial Soils

Polyhalogenated carbazoles?PHCZs?are a kind of heterocyclic compounds containing nitrogen.PHCZs have caused wide concerns because of their persistence in the environment and dioxin-like toxicities.However,researches about the sources,environmentaldistributionandtransportation,and bioaccumulation/magnification of PHCZs are scarce.Soil is suggest to be one of the most important source and sink of PHCZs in the environment:First,soil is a possible natural origin of PHCZs;Then,PHCZs from other sources may finally deposit in soil since most of PHCZs are hydrophobic.Therefore,studies about the bioaccumulation and toxicities of PHCZs in soils are important to evaluate the ecological risks of these compounds.In the present thesis,the bioaccumulation and ecotoxicities of 1,3,6,8-tetrabromocarbazole?1368-BCZ?in earthworms from spiked artificial soils were studied.The main results are as follows:1.Based on the adsorption isotherm of 1368-BCZ adsorbed by earthworm dry powder and artificial soil,the partition coefficients of 1368-BCZ between soil phase and water phase,and between earthworm phase and water phase were 0.24×10³,and 5.73×10³,respectively.According to the equilibrium partition model,the estimated values of bioaccumulation factor?BAF?,bio-soil accumulation factor?BSAF?,and bioconcentration factor?BCF?of 1368-BCZ under adsorption equilibrium state were 6.21,12.87 and 9.06,respectively.2.The absorption rates of earthworm were 0.92 g_soil-dwoil-dw g^-1_earthworm-dwd^-1and 0.36g_soil-dwoil-dw g^-1_earthworm-dwarthworm-dw d^-1,respectively,with exposure concentrations of 20 ng/g and100 ng/g.And the corresponding removal rates were 0.085 d^-1and 0.091 d^-1,respectively.3.At the end of 28 days of exposure,the enrichment of 1368-BCZ in earthworms reach the equilibrium stage.In steady stage,the BAF and BSAF values of 1368-BCZ for 20 ng/g dw group were 10.06 and 2.7,respectively,while those for 100 ng/g dw group were 4.18 and 1.12,respectively.The desorption of 1368-bcz from soil is related to the concentration of this substance in soil.As the increasing concentration of 1368-bcz in soil,the desorption rate decreased,which led to lowed bioavailability.4.Activities of glutathione?GSH?,glutathione peroxidase?GPx?,superoxide dismutase?SOD?,catalase?CAT?,malondialdehyde?MDA?,and acetylcholinesterase?AChE?of the earthworms changed under the exposure of1368-BCZ.The results showed that on the 5^thh day of exposure,GSH levels under100 ng/g 1368-BCZ reached the highest activity?4.9 nmol/mgprot?,which was 2.13times and 2.08 times of that in the blank control group and 20 ng/g dw group,respectively.On the 10 ^thh and 14 ^thh day of exposure,the activity of SOD in the experimental group was significantly different from that in the blank group?P<0.01?.On the 10 ^thh and 14 ^thh day of exposure under 100 ng/g 1368-BCZ,the level of MDA was significantly higher than that of the blank group?P<0.05?.However,MDA level showed no significant difference when compared to that of the control at the later stage of exposure?>14 d?.These results indicate that when the spiked concentration of 1368-BCZ in soils reached to 100 ng/g,the target compound bioaccumulated in the earthworns can cause oxidative damage to the organism.However,the damage can be recovered through the self-regulation of earthworms.The effect of 1368-BCZ on AChE was inhibited,with the maximum inhibitory rate to be 27%.The results imply that 1368-BCZ is neurotoxic against earthworms.By contrary,the activities of GPx and CAT were not significately changed when compare the data between the exposure groups and the blank control group.