Effects Of Cu On The Fate Of BDE-28 In Soil And Soil-Pakchoi System

Polybrominated diphenyl ethers(PBDEs)are widely used as additive flame retardants in plastics,textiles and all kinds of electronic and electrical products.It has been found that PBDEs have endocrine disruption effects,neurotoxicity and potential carcinogenicity.PBDEs have been phased out in Europe and North America market;however,China is still the major producer of BDE-209 that tends to be released to the environment.Besides,a large amount of electronic and electrical waste has been transported to southeastern China.The process of e-waste dismantling caused serious PBDEs pollution to environment,and this pollution is usually accompanied with heavy metals,especially copper.Soil is an important sink of pollutants,and it is significant to study the fate of pollutants in soil.Aging of organic pollutants in soil could form bound residues,which is considered to reduce the environmental risk of them.However,there is few study about the bound residues formed by PBDEs in soil.And the effects of heavy metals on the fate of PBDEs in soil and the transfer of PBDEs to plant have not been well studied yet.These studies will be of significance to do comprehensive evaluation about the environmental risk of PBDEs.We chose 2,4,4’-tribrominated diphenyl(BDE-28)and copper as representatives to carry out relevant research.Considering the complex soil environment,isotope tracer technique was used to overcome some shortages of general methods.The main contents and conclusions are as follows:(1)14C-BDE-28 was synthesized by condensation reaction of 14C-4-bromophenyl and 2,2’,4,4’-Tetrabromodiphenyliodonium chloride,which provides the basis of subsequent experiments.(2)With the addition of different concentrations of Cu2+(0,200,and 500 mg/kg,in the form of CuCl2),the fate of BDE-28 in oxic soil after 290 days’ incubation was studied.It included mineralization,the extractable and bound residues,and the fractionation and present form of bound residues of BDE-28.It was found that BDE-28 in soil was extremely stable,and after 290 days there was only 2%of mineralization;the percentage of bound residues was 10%and mainly distributed in humin with 54%-56%being physically bound;there was no metabolites detected.The addition of Cu inhibited the mineralization and the formation of bound residues of BDE-28 significantly,and the effect of 500 mg/kg Cu2+was more obvious than 200 mg/kg Cu2+.(3)In soil-plant system with different levels of Cu in soil,we studied the fate of BDE-28 in soil as well as the effect of Cu on the bioaccumulation and distribution of radioactivity in pakchoi.We found that the extractable radioactivity in planted soil was reduced,but amounts of bound residues between planted soil and unplanted soil had no obvious difference.The effects of Cu on the fate of BDE-28 in the soil-pakchoi system is not remarkable.In summary,BDE-28 was extremely hard to degrade in soil.The coexistence of Cu with BDE-28 increased the persistence of BDE-28 in soil and possible bioavailability,thus increasing the environmental risks of BDE-28.Although we did not find obvious difference of accumulation of radioactivity in pakchoi with different levels of copper in soil,pakchois promoted the distribution of bound residues in humic acid and fulvic acid leading to the increase of transport of the bound residues in soil.Therefore,factors like heavy metals and plants should be taken into consideration when carrying out the risk assessment of PBDEs for correct evaluation.