The Phytoremediation Of Decabromodiphenyl Ether Polluted Soil In E-waste Dismantling Area

Currently, the environmental pollution problems in non-standard electronic dismantling area have caused the state great attention, among which the most important concern is soil pollution problems caused by brominated flame retardants polybrominated diphenyl ethers (PBDEs). It is particularly urgent to carry out remediation research for soil polluted by BDE-209in typical electronic dismantling region. This is significance to ensure the safety and security of the national ecological environment and human health.The decabromodiphenyl ether (BDE-209) was selected as the representative of the brominated flame retardant. Pot experiment using root bags to obtain rhizosphere soil was conducted to study the phytoremediation of BDE-209by different plant collected from Taizhou and Wenling joint area, Zhejiang province of China, where has been well-known as one of the biggest electronic dismantling base. The main findings are as follows:The method based on ultrasonic extraction-GC-uECD for the analysis of residual BDE-209in soil was established by optimizing the extraction conditions as well as considering the effects of different purification columns, eluting agents on the recovery efficiency. With this method, the average recovery of BDE-209reached93.4%. Representative soil samples, collected from the main administrative villages (including Tongshan, Mukeng, Zeguo, Anrong, Yuluyang and etc.) in Taizhou and Wenling joint area, were thereafter analyzed for BDE-209residues using this method. The concentration of BDE-209residue in these areas was between49.9ug kg-1and1539.1ug kg-1, among which Mukeng was the most seriously polluted area.The most seriously polluted soil in Mukeng was further used for pot experiment. Among the four representative rice species (Huanghuazhan, Liangyoupeijiu, Fengyou22, Shanyou63) in Zhejiang and Jiangsu province, Huanghuazhan was screened out as a BDE-209-tolerant rice variety. Then the selected rice variety Huanghuazhan along with other six local plant varieties (including zucchini, tall fescue, milk vetch, alfalfa, ryegrass, Xiushui134) were used to conduct the phytoremediation study of BDE-209soil. The results showed that in the study period, the concentration of BDE-209decreased both in the aged and the newly amended polluted soil. The BDE-209dissipation rates were higher in the aged soil than the newly amended soil both with and without plantation. The BDE-209dissipation rates of different plants were different. In the aged soil, BDE-209dissipation rates were sorted as:Xiushui134> ryegras> Huanghuazhan> pumpkin> tall fescue> alfalfa> milk vetch, among which Xiushui134was the most effective with a dissipation rate of52.87%; In newly amended soil, the order of BDE-209declined rates was:alfalfa, ryegrass> Huanghuazhan> Xiushui134> milk vetch> tall fescue> pumpkin, where the BDE-209dissipation rate of alfalfa was28.29%. The rhizosphere effects of different plants for facilitating BDE-209dissipation were further investigated, and the results showed that in the aged soil, Xiushui134was the most effective; while in the newly amended soil, the ryegrass was more competitive for accelerating BDE-209dissipation.The phospholipid fatty acid (PLFAs) technology was used to analyze the characteristics of the rhizosphere microbial community structure under different agronomic management practices. The rhizosphere effect of phytoremediation for BDE-209polluted soil was discussed by combining the critical soil enzyme activity with the dynamic changes of carbon, nitrogen and iron, during the remediation period. The results showed that, compared with the control treatment without plantation, both in the aged and the newly amended soil, the total PLFAs and the characteristic fatty acids in rhizosphere increased in soils with plantation, which showed that growing plants promoted rhizosphere microbial growth. The principal component analysis (PCA) was then used for analyzing PLFAs of different plant rhizosphere. It was found that PC1and PC2together explained52.6%of the variation in the microbial community structure. Further correlation analysis between the BDE-209dissipation rate and rhizosphere soil PLFAs characteristics showed that:in the aged soil, the dissipation rate of BDE-209had significant negative correlation with actinomycetes and cyclopropyl fatty acids, while was significantly positive correlated with mono-unsaturated fatty acids (P<0.05); in the newly amended soil, the dissipation rate of BDE-209was significant positive correlated with bacteria, Gram-positive bacteria, and mono-unsaturated fatty acids (P<0.05). The intrinsic relationships of BDE-209dissipation behavior were also analyzed with the activities of soil catalase and dehydrogenase, as well as the content of dissolved organic carbon (DOC), iron ions [Fe(â…¢) and Fe(â…¡)], nitrate nitrogen, and ammonium nitrogen. The results showed that, in the aged soil, the dissipation rate of BDE-209had significant negative correlation with the activity of soil catalase, and highly significant positive correlation with the activity of soil dehydrogenase and the content of DOC and Fe(â…¡); in newly amended soil, the dissipation rate of BDE-209had significant positive correlation with the content of Fe(â…¢).