| Decabromodiphenyl ether(BDE-209)is one of the most widely used brominated flame retardants(BFR),the environmental pollution problems caused by BDE-209 cannot be ignored.Soil is the major sink of PBDEs in the environment.If we master the transformation and biological effects in different crops when pollutants entered the soil,it will be beneficial to the environmental safety evaluation and the formulation of pollution prevention and control policies.The study used 14C tracing method combined with modern instrument analysis technology to fully demonstrated the uptake,translocation,and fate of BDE-209 in contaminating soil-rice system and rotation contaminated soil-vegetable system by labeling the key molecular framework of BDE-209 with 14C.Our study clarified the kinetics of extractable residues,bound residues,degradation and dissipation of BDE-209 in soil-rice/vegetable systems.Meanwhile,due to the strong retention characteristics of[14C-U-Benzene]-BDE209 in the soil,we preliminary investigated the degradation of PBDEs in soil by E-beam irradiation.The main research outcomes are described below:1.The results confirmed the different[14C-U-Benzene]-BDE209 absorption,accumulation and metabolism/degradation in different rice cultivars.The cultivar of Huanghuazhan(HHZ,indica)had the greatest whole-plant 14C absorption but the lowest ?PBDEs residues in its grain,compared with Yudao 1(YD1,indica)and Ningjing 3(NJ3,japonica).Concentrations of ?PBDEs derived from[14C-U-Benzene]-BDE209 were 421.8,454.2,and 967.0 ng g-1 for HHZ,YD1,and NJ3,respectively.The mass percentage of[14C-U-Benzene]-BDE209 was 90%?3 1%and 50%for HHZ,YD/1,and NJ3,respectively.The EDI of ?PBDEs were predicted to be 928,1056,2675 ng kg-1 bw d-1 via consuming rice grain from HHZ,YD1,and NJ3,respectively,and monomer levels of[14C-U-Benzene]-BDE209 and its metabolites are lower than the safe limits for human consumption recommended by US-EPA.The results suggest that the public health risk associated with consumption of rice grown in PBDEs-polluted environments could be reduced through judicious selection of suitable rice cultivars This study implies that cultivar differences must be taken into consideration in assessing the dietary risks of PBDEs or using phytoremediation for PBDE contaminations2.In rice-vegetable rotation,the absorption and accumulation of[14C-U-Benzene]-BDE209 and its metabolites were different in different vegetables.The concentration of 14C in the roots of eggplant and pepper were higher than peanut,while the concentration of 14C in the grain of peanut was significantly higher than eggplant and pepper(P<0.05).The translovation factor of peanut was higher than eggplant and pepper.The estimated daily intake for vegetables by an adult was 0.01 to 0.07 ?g BDE-209-equivalent kg-1 bw day-1,which is at least two orders of magnitude below the acceptable oral dose suggested by U.S.EPA(7 ?g kg-1 bw day-1)3.Rice-vegetable crop rotation significantly enhanced the degradation and dissipation of BDE-209 in the soil(P<0.05).After rotation with peanut?eggplant and pepper,the mole percentage of BDE-209 decreased by 22.9%,22.6%and 24.8%,respectively;the dissipation of BDE-209 increased by 19.0%,4.0%and 19.3%,respectively,compared with the rice cultivation.In the soil cultivated with eggplant,peanut and pepper,the main degradation product is dibromodiphenyl ether.In the control soil,the main degradation product is pentabromodiphenyl ether.The bound residues formation in soil was<3%,BDE-209 and its metabolites in the soil mainly exist in the form of extractable residues(>73%),the bioavailability of BDE-209 and its metabolites was low(<0.23%).Our work confirms that crop rotation from rice to vegetable enhanced the dissipation and degradation of BDE-209 in the soil,and provide an insight into the soil remediation of environmental pollutants3.E-beam irradiation is effective in the remediation of BDE-209 contaminated soil.The degradation of BDE-209 in soil followed the pseudo-first-order kinetic relationship.The D50 values of BDE-209 in non-flood soil RES,RPS and RCS were 4.32,7.24 and 3.61 kGy,respectively.The D50 values of BDE-209 in flood soil RES,RPS and RCS were 10.16,13.00 and 12.30 kGy,respectively.The debromination of BDE-209 was contributed by the E-beam irradiation and generated lower brominated diphenyl ethers.However,the E-beam irradiation didn't contribute to the mineralization of BDE-209,more than 86%of 14C remains in the soil.This research initially confirmed the feasibility of the remediation of PBDEs contaminated soil by E-beam irradiation... |
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