| Decabromodiphenyl Ethane（DBDPE）,as an environmentally friendly new type of brominated flame retardant（NBFRs）,has good stability,strong UV resistance,and no harmful substances are found during the combustion process.It is an ideal substitute for commercial decabrominated diphenyl ether（BDE-209）.However,DBDPE shares similar characteristics with BDE-209,such as the potential for long-distance environmental migration,environmental persistence,bioaccumulation,and toxicity.It has been detected in different environmental media.DBDPE has strong hydrophobicity and is mainly contained in solid media such as soil and sediment.Therefore,environmental health risks associated with the production and use of DBDPE must be identified.This article by DBDPE as the research object and compares the photodegrada tion effects of DBDPE in four typical types of soils from different regions using UV and simulated natural light.Through HPLC analysis,the light source,initial conce ntration,and soil are investigated.The effect of particle size,p H,HA and other factors on the photolysis effect of DBDPE;The photolysis kinetics of DBDPE under different light sources was investigated.By detecting the bromide ion concentration of the reaction solution,UV-Vis absorption spectroscopy（UV-Vis）,Fourier infrared spectrophotometer（FTIR）and Electron paramagnetic resonance（EPR）methods,proposed the preliminary reaction state of DBDPE in Tetrahydrofuran（THF）solution,the photodegradation mechanism of DBDPE was studied.This study is of great significance for the study of the photodegradation of DBDPE in soil.The main findings are as follows:The degradation of DBDPE in soil under ultraviolet light and simulated natural light accorded with first-order kinetics.The degradation effect of DBDPE under UV light was significantly stronger than that under simulated natural light.The degradation rate of DBDPE under UV light for 72h was 15.5%higher than that under simulated natural light for 90d.The results of the degradation of DBDPE in soil by ultraviolet light showed that the long-polluted soil reached the state of adsorption equilibrium under 72h UV light.However,the longer the soil was polluted,the worse the degradation of DBDPE was.The degradation rate of soil polluted for 90 days was 33.9%lower than that of soil polluted for 15 d.Soil types also affect the photolysis rate.Under 72h UV irradiation,the degradation effect of aeolian sand soil was the best,and the photolysis half-life of chernozem soil was shortened by 27.37 h compared with that of chernozem soil with the slowest degradation.The degradation rate of DBDPE was positively correlated with the soil particle size.The degradation rate of DBDPE in the aeolian sand soil with a particle size of 60 mesh was14%lower than that with a particle size of 40 mesh,and the half-life of DBDPE was increased by10.79 h.The degradation rate of DBDPE was 66.2%-84.5%in the range of 2-40 mg·kg-1,and the half-life of photolysis increased from 74.52 h to 114.93 h.When p H was alkaline,DBDPE had a better photodegradation effect in soil and the degradation rate reached 71.1%.Humic acid（HA）inhibited the photodegradation of DBDPE in soil.The increase of ultraviolet light intensity is beneficial to the photodegradation of DBDPE in soil.A proper amount of catalyst（Ti O 2）was added to promote the photodegradation of DBDPE.The results of simulating natural light degradation of DBDPE in soil showed that the effects of soil particle size,initial concentration,p H,HA concentration and other influencing factors were consistent with the effects of ultraviolet light degradation of DBDPE.Increasing soil particle size and p H promoted the degradation of DBDPE.The degradation rate of DBDPE was 4.1%and the half-life of DBDPE was 4.05 d in the aeolian sand soil with the grain size of 60 mesh and 40 mesh.The degradation rate of DBDPE in alkaline soil was 12.7%higher than that in acidic soil,and the photolytic half-life of DBDPE was shortened 14 d.Increasing the initial concentration and HA concentration inhibited the degradation of DBDPE.The degradation rate of DBDPE at the lowest concentration was increased by 13.2%compared with that at the highest concentration,and the half-life of DBDPE was shortened by 42.02 d.When HA concentration was in the range of5-20mg·g-1,the half-life of degradation increased from 138.88d to 153.66 d.The degradation mechanism in THF media showed that the increase of bromide ion concentration and the red shift of absorbance indicated that the initial debromination reaction occurred in the process of DBDPE.The results of FTIR analysis showed that the benzene ring skeleton of the degraded DBDPE was stretched and the carbonyl group（C=O）was involved in the reaction.Through the addition of quenching agent and EPR experiment analysis,six characteristic peaks of the spin adduct were detected.The addition of benzene quinone,a quenching agent,significantly inhibited the degradation of DBDPE,so it was confirmed that·O2-free radical was the main active group in the degradation process.Finally,a total of 13 int ermediate products were identified by liquid chromatography-triple quadrupole mass spectrometry（LC-MS/MS）,which were debrominated products,oxidation products and hydroxylated products.Three possible degradation pathways,including reductive debromination,oxidation of C-C bond and hydroxyl substitution,were speculated based on the identification of intermediate products. |
