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Hydroxy polybrominated diphenyl ethers induced degradation mechanisms and kinetics of atmospheric optical quantum chemical study

Author: ZhouJing
Tutor: QiaoXianLiang；ChenJingWen
School: Dalian University of Technology
Course: Environmental Science
Keywords: Australia on behalf of more than diphenyl ethers Hydroxyl radicals Density functional theory Response mechanism Rate constant
CLC: X820.4
Type: Master's thesis
Year: 2011
Downloads: 144
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Abstract


Semi-volatile organic compounds (SOCs) are a class of low vapor pressure and strong lipophilic compounds, such compounds are widely distributed in environmental media, and the ecological environment and human health, cause serious harm. In the troposphere, there is generated by a photochemical process-OH radicals, these. OH radicals in atmospheric photooxidation SOCs play an important role in the degradation process. · OH induced SOCs oxidation reaction is atmospheric SOCs remove the main way. Therefore, atmospheric research SOCs indirect light degradation reaction mechanisms and kinetics data for ecological risk assessment is of great significance. Currently, many methods have been used to study experimental and SOCs. OH reaction mechanism and the determination of kinetic constants, but almost all of the experimental method has time consuming and expensive, depending on the equipment and other disadvantages not able to meet the growing organic Commodities ecological risk assessment needs, so must develop theoretical calculation. Quantitative structural relationships (QSARs) is a commonly used model to predict the physical and chemical properties of chemicals as well as the theory of kinetic constants calculated. Currently, there have been many QSARs models were developed to predict the organic compound and hydroxyl radical reaction rate constant (kOH). Although, QSARs model has low computational cost and a better result, but QSARs model depends on the experimental data and the model can be used within the application domain. Compared with QSARs model, quantum chemistry calculation method in predicting reaction mechanisms and kinetic data has unparalleled advantages. Density functional theory (DFT) and statistical mechanics, the lack of experimental data in the case of chemical thermodynamic data for the main reaction pathways and predicted degradation products, and give the corresponding rate constant, the reaction branching ratio and product distribution of kinetic information. In the present study, selected BDE-15 as a case study, showing the DFT can be successfully used to predict the polybrominated diphenyl ethers (PBDEs) and · OH atmospheric photo-oxidation degradation reaction mechanisms and kinetics. Through quantum chemical calculations and master equation to predict the occurrence of PBDEs · OH oxidation reaction triggered by the main degradation product was Hydroxy polybrominated diphenyl ethers (HO-PBDEs), bromophenol and bromine. Meanwhile, the predicted 298 K under the reaction rate constant (kOH) agreement with experimental results. In addition, the two generated HO-PBDEs paths are identified: (1) PBDEs the Br atoms are substituted · OH; (2) BDE-OH adduct, · OH attached hydrogen atoms on carbon atoms by O2 \take. \This study provides an efficient means to study atmospheric PBDEs indirect light degradation mechanisms and kinetics.

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CLC: > Environmental science, safety science > Environmental Quality Assessment and Environmental Monitoring > Analysis and Evaluation of Environmental Quality > General issues > Risk Assessment
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