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题名: 毒性有机污染物与NO3/N2O5的大气化学反应研究
作者: 王友峰
学位类别: 博士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 束继年
关键词: 气溶胶质谱,非均相反应,农药,多环芳烃,反应机理,aerosol mass spectrometer, heterogeneous reaction, pesticide, PAHs, reaction mechanism.
其他题名: Atomospheric Reactions of Typical Organic Pollutants with NO3/N2O5
学位专业: 环境科学
中文摘要:     农药和多环芳烃是大气环境中两类典型的毒性有机污染物。随着工农业的快速发展,它们经人为源被大量排放进入大气中,发生一系列迁移转化过程,从而对人体健康和生态环境产生重要的影响。本研究选取一些典型的有机农药,研究了它们在大气环境中与NO3/N2O5混合体系非均相反应的反应产物、反应机理和反应动力学等。并使用量子化学方法对一些有争议的转化机理,如有机磷农药中P=S双键转化为P=O双键的机理和多环芳烃与N2O5的反应机理等进行了理论计算。研究结果有助于认知农药和多环芳烃的夜间大气化学行为和这些污染物的潜在危害与来源解析。具体研究结果如下:
    (1)使用烟雾箱、真空紫外光电离气溶胶质谱仪和大气气体分析质谱仪在线研究了拟除虫菊酯类农药灭虫菊、苯醚菊酯和氰戊菊酯与NO3自由基的非均相反应。以异戊二烯为参比物,运用混合相相对速率法测得了实验条件下颗粒相灭虫菊、苯醚菊酯和氰戊菊酯与NO3自由基的非均相反应的反应速率分别是(5.54 ± 0.14) × 10-12, (1.61 ± 0.03) × 10-12, 及 (1.86 ± 0.04) × 10-12 cm3 molecule-1 s-1。结合在线气溶胶质谱仪的分子离子峰和GC-MS离线分析的EI峰特征,确定了灭虫菊与NO3自由基非均相反应的7种产物,苯醚菊酯与NO3自由基非均相反应的3种产物,和氰戊菊酯与NO3自由基非均相反应的4种产物。
    (2)利用烟雾箱、真空紫外光电离气溶胶质谱仪和大气气体分析质谱仪在线研究了甲基嘧啶磷和抗蚜威两种农药与NO3自由基的非均相反应。甲基嘧啶磷和抗蚜威的分子结构具有典型农药的代表性特征,都含有一个N,N-dialkyl连接在嘧啶环上。运用混合相相对速率法,以异戊二烯为参比物,测定了实验条件下悬浮态甲基嘧啶磷和抗蚜威颗粒与NO3自由基的非均相反应速率分别是(9.9 ± 0.3) × 10-12 和 (7.5 ± 0.3) × 10-13 cm3 molecule-1 s-1。确定了甲基嘧啶磷颗粒与NO3自由基非均相反应的3种产物和抗蚜威颗粒与NO3自由基非均相反应的5种产物,其中phosphoric acid 2-diethylamino-6-methyl-4-pyrimidinyl dimethyl ester 和2-(dimethylamino)-5,6-dimethyl-4-hydroxy-pyrimidine分别是甲基嘧啶磷和抗蚜威与NO3自由基非均相反应的主要产物。又甲基嘧啶磷是一种典型的有机磷农药,其P=S双键转化为P=O双键的反应机理一直备受关注。由于实验方法难以确定该反应的中间体和过渡态等信息,本研究采用量子化学方法和密度泛函理论对NO3自由基引发的甲基嘧啶磷中P=S双键转化为P=O双键的反应机理进行了理论计算,结合热力学分析,得到了合理的中间体和过渡态结构,为其他相似有机磷化合物的降解机理研究提供了依据。
    (3)在N2O5、NO3和NO2共存的体系中,多环芳烃和N2O5的反应很难与其和NO3/NO2的反应区分开。采用量子化学理论计算方法和密度泛函理论对目前尚有争议的荧蒽和芘与N2O5的反应机理(双分子亲核取代反应机理(SN2)和均裂反应机理)进行了计算。并使用正则变分过渡态理论和TheRate Programme软件对每种反应机理的反应速率进行了计算。通过对反应能垒、焓变和吉布斯自由能变等热力学信息及动力学信息的分析,发现SN2反应机理要比均裂反应机理更适用于荧蒽和芘与N2O5的反应。此外,用同样的方法计算了荧蒽和芘先与NO3加成,再与NO2反应的能垒、焓变和吉布斯自由能变,并与荧蒽和芘与N2O5的反应进行了对比。结果表明,荧蒽和芘与NO3/NO2反应的主要产物分别是2-nitrofluoranthene和2-nitropyrene;荧蒽和芘与N2O5反应的主要产物分别是3-nitrofluoranthene和1-nitropyrene。理论计算得到荧蒽和芘与N2O5反应的速率常数分别是2.50 × 10-27和2.16 × 10-24 cm3 molecule-1 s-1,要比与NO3/NO2的反应速率低7~10个量级,说明N2O5在与多环芳烃的气相反应中并不是一种有效的硝化剂,这也表明大气中含量较多的3-nitrofluoranthene和1-nitropyrene可能来源于一次排放或非均相反应。
英文摘要:     Pesticides and polycyclic aromatic hydrocarbons (PAHs) are two kinds of typical toxic organic pollutants in atmospheric environment. Most of their emissions are anthropogenic with the rapid development of industry and agriculture. The transportation and transformation of these pollutants directly affects the atmospheric environment and human health. In this study, the heterogeneous reactions of a number of widely used pesticides with NO3 radicals are investigated. The reaction products, pathways and reactive constants are obtained in this study. Besides, high level quantum chemistry calculations have been use to study some controversial transformation mechanisms, including the NO3-initiated oxidation mechanism of P=S bond into P=O bond of pirimiphos-methyl (PMM), and the reaction mechanism of PAHs with N2O5. The results are meaningful on understanding the atmospheric behavior of these pollutants and their potential harms and the source apportionment. The detailed findings are as follows:
    (1) The heterogeneous reactions of pyrethroid pesticides (i.e. resmethrin, phenothrin, and fenvalerate) are investigated in a smog chamber, equipped with a real-time vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS), and an online atmospheric gas analysis mass spectrometer. The effective rate constants of the pyrethroid particles in the reaction with NO3 radicals are determined by a mixed-phase relative rate method with isoprene as the reference compound. The obtained heterogeneous reaction rate constants of the resmethrin, phenothrin, and fenvalerate with NO3 radicals are (5.54 ± 0.14) × 10-12 , (1.61 ± 0.03) × 10-12, and (1.86 ± 0.04) × 10-12 cm3 molecule-1 s-1, respectively. The reaction products are detected and suggested based on the molecular ion peaks from VUV-ATOFMS and EI characteristic ion peaks of GC-MS analyses. Seven products for resmethrin, three products for phenothrin, and four products for fenvalerate are assigned in the heterogeneous reactions with NO3 radicals.
    (2) The heterogeneous reactions of pirimiphos-methyl (PMM) and pirimicarb (PM) are investigated in a smog chamber with a real-time vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS), and an online atmospheric gas analysis mass spectrometer. PMM and PM belong to the two kinds of the widely used pesticides with typical structures that contain an N,N-dialkyl adjacent to the pyrimidine ring. A mixed-phase relative rate method is used to determine the heterogeneous reaction rates with the isoprene as the reference compound. Under the experimental conditions, the heterogeneous reaction rates of particle-phase PMM and PM with NO3 radicals are (9.9 ± 0.3) × 10-12 and (7.5 ± 0.3) × 10-13 cm3 molecule-1 s-1, respectively. Three products are assigned and phosphoric acid 2-diethylamino-6-methyl-4-pyrimidinyl dimethyl ester is the major product for the reaction of PMM with NO3 radicals. Five products are assigned and 2-(dimethylamino)-5,6-dimethyl-4-hydroxy-pyrimidine is the major product for the reaction of PM with NO3 radicals. Besides, PMM belongs to the typical organothionophosphorus pesticides that have a P=S double bond. There are many debates on the transfermation mechanism of P=S bond into P=O bond for organothionophosphorus compounds. Due to the defect of experimental studies on detecting the intermediates and transition states, we conduct a quantum chemical calcualtion on the NO3-initiated oxidation mechanism of P=S bond into P=O bond of PMM. The theoretical studies present the reasonable intermediates and transition states, which may provide useful information for understanding the degradation mechanism of organothionophosphorus compunds in the environment.
    (3) The product assignment for gas-phase reaction of PAHs with NO3/NO2 and N2O5 is perplexing for many years due to the coexistence of NO3/NO2 and N2O5. We conduct a quantum chemical calculation using the density functional theory (DFT) to study the reaction mechanisms of fluoranthene (FL) and pyrene (PY) with N2O5, which are controversial for years. The SN2 reaction mechanisms for N2O5 are elucidated in detail and the homolytic mechanisms are calculated for the first time. The reaction energy barrier, enthalpies and Gibbs free energies are calculated and analyzed. A comparison of these two reaction mechanisms shows that SN2 reaction mechanisms are more suitable for interpreting N2O5 direct reactions. Rate constants for the fluoranthene and pyrene reactions with N2O5 are deduced for the first time using canonical variational transition state theory (CVT) by TheRate Programme, which are found to be 2.50 × 10-27 and 2.16 × 10-24 cm3 molecule-1 s-1, respectively at 298 K. These rate constants are about 7~10 orders of magnitude lower than those of FL and PY in reactions with NO3/NO2. The kinetic results rule out N2O5 as an effective nitrating agent in the gas phase, indicating that 3-nitrofluoranthene and 1-nitropyrene observed in the atmosphere mainly derive from heterogeneous reactions or primary emissions.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34443
Appears in Collections:大气环境研究室_学位论文

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Recommended Citation:
王友峰. 毒性有机污染物与NO3/N2O5的大气化学反应研究[D]. 北京. 中国科学院研究生院. 2015.
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