Simulation Research On The Natural Degradation Process Of PBDEs And TBBPA In Polluted Soil Of E-waste Dismantling Area Under The Changes Of Atmospheric Environment

At present, the contents of Poly Brominated Diphenyl Ethers(PBDEs) andTetrabromobisphenol A(TBBPA) in the soil from e-waste dismantling area are obvious higherthan the average level of cities. PBDEs and TBBPA have been detected in environmentalmedium and organisms, which pose a threat to the health of ecological system and humanbody. Approaches of PBDEs and TBBPA disappear from environment system is advectionoutput from atmosphere and soil degradation. The previous studies focused on the analysis ofintegral characteristics of PBDEs and TBBPA from the e-waste disposal area. However, thereis little research of PBDEs and TBBPA natural degradation on the background of globalclimate change in the soil from e-waste disposal.Currently, the trend of global climate change mainly reflected in the following aspects:The rising levels of CO2, CH4, N2 O and other greenhouse gases in atmospheric environmentlead to global warming. The stratospheric ozone loss caused UV-B ultraviolet radiationincreases in the surface. In addition, the phenomenon, ozone concentration increased onsurface, happened in the area of higher NOx emission level. Ozone pollution is increasinglyserious. The increased O3 concentration and high emissions of SO2 and NOx caused thefrequent phenomenon of acid rain, The acid rain area showed a trend of expanding and acidifythe soil.Therefore, object this research is PBDEs and TBBPA pollution soil, and theconcentrations of PBDEs and TBBPA are similar to soil pollution levels of the pearl riverdelta e-waste dismantling area. Under the global climate change trend, changing theatmospheric environment of experiment to explore the effects of ozone, irradiation,temperature and soil p H on the natural degradation processes of PBDEs and TBBPA in thepolluted soils. The main results were as follows:The oxidation of ozone can effectively promote the natural degradation of PBDEs andTBBPA in soil, the degradations influence by ozone concentration, soil depth and the aerationtime. The degradation reaction rate of PBDEs and TBBPA increased with an rise in ozoneconcentration but decreased with increasing soil depth. In two hours, 0.3 mg L-1ozone lead tomore than 99% of BDE-209 degraded into less-brominated BDEs(from BDE-28 toBDE-183), meanwhile, 33.37% of TBBPA removed on the surface soil. When theconcentration of ozone rised to 10 mg L-1, the removals of less-brominated BDEs and TBBPAwere 63% and 90.37% on the surface soil and 1% and 80.26% on the deep soil. Thedegradation rate of PBDEs and TBBPA improved with the increasing of aeration time, whenthe concentration of ozone was 0.3 mg L-1, after 256 hours, the removals of less-brominatedBDEs and TBBPA were 83% and 98.86% on the surface soil.From the view of molecular structure, PBDEs and TBBPA have double benzene ringstructure, which can absorb the ultraviolet ligh. Photodegradation efficiency effected by lightintensity and illumination time. The degradation of PBDEs and TBBPA occur independentlyunder continuous or discontinuous exposure. The photodebromination rate of PBDEs andTBBPA increased with increasing light intensity. The photodegradation reactions underUV-lamp irradiation were faster than that of the reaction under solar irradiation. Under 8 hultraviolet illumination 82% of less-brominated BDEs generated, at the same tme, while theless-brominated BDEs under the sun light is only 40%. 41.23% of TBBPA has been removedunder UV-lamp irradiation in 2 h, but under the sun light it has to continued to 16 h to reach44.28% removal rate. When the solar lighting continued to 256 h, the less-brominated BDEsaccumulated 99% and TBBPA degradation rate was 67.88%. It can be seen photodegradationprocess is the important degradation pathways for PBDEs and TBBPA in the naturalenvironment.The condition of high temperature contributed to the degradation and transformation ofPBDEs and TBBPA. The degradation rate of BDE-209 was slow under the temperature of25℃, until the 30 th day only 25% of less-brominated BDEs generated. Under the temperatureof 40℃, less-brominated BDEs accumulated to 24% in the 5th day and in 18 th day up to amaximum of 98%, then the less-brominated BDEs degraded gradually. The removal rate ofTBBPA also presents a good positive correlation with the environment temperature in the soil.Contrasting the concentration of PBDEs and TBBPA in the four groups of the soil samples, itcould be observed that the order of degradation intensity was p H=9.0 > p H=5.0 > p H=2 >p H=7.58, indicating that the degree of degradations of PBDEs and TBBPA were higher forsamples with a p H change than those without p H change. An alkaline and faintly acid soilenvironment were more conducive to the degradation and migration of PBDEs and TBBPA.The research results show that the global warming caused by the rising concentrations ofCO2 and greenhouse gases, and the phenomenon of acid rain caused by the risingconcentrations of SO2, NOx and O3 in the atmospheric environment may be promote thedegradation and transformation of PBDEs and TBBPA in the nature environment.