| 题名 | 大气中颗粒相多环芳烃与N2O5/NO3/NO2的非均相化学反应研究 |
| 作者 | 张鹏 |
| 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 | 多环芳烃 NO3自由基 O3 非均相反应 湿度，PAHs,NO3 Radical, O3, Heterogeneous Reactions, Humidity |
| 其他题名 | Heterogeneous reaction of particulate polycyclic aromatic hydrocarbons (PAHs) with N2O5/NO3/NO2 in the atmosphere |
| 学位专业 | 环境科学 |
| 中文摘要 | 多环芳烃是大气环境的典型致癌致畸类有机污染物，它们经人为源大量排放进入大气中,它们在大气中的迁移转化直接影响着大气环境气候和人类健康。本论文针对 颗粒相多环芳烃机污染物与N2O5/NO3/NO2的非均相反应进行了研究。研究内容主要包括反应产物、反应机理及反应动力学等。研究结果将有助于认知多 环芳烃的大气化学行为以及其带来的潜在环境危害。具体研究结果如下： （1）利用烟雾箱、真空紫外光电离气溶胶飞行时间质谱仪及气相质谱仪在线研究了两种五环类多环芳烃benzo[b]fluoranthene （B[b]F） 和 benzo[k]fluoranthene（B[k]F）与NO3自由基的非均相反应。共九种mono- NB[b]F（保留时间依次为：49.57, 50.60, 51.42, 51.68, 52.23, 52.33, 52.62, 53.06, and 54.07 min）和2种di-NB[b]F（保留时间：55.6 and 56.1 min）以及4种单硝基mono-NB[k]F (保留时间依次为：50.0, 51.4, 52.2, 和 53.4 min) 和一个双硝基 di-NB[k]F (保留时间为 59.5 min)生成。 我们推测本实验GC-MS所观察到四种mono-NB[k]F 依次分别为：7-，1-，8-，和3-NO2-NB[k]F以及唯一的di-NB[k]F为3,7-NO2- B[k]F。其它几种仅仅由VUV-ATOFMS观察到的产物为：tri- NB[b]F, mono-NB[b]F-quinone 和di-NB[b]F-quinone以及B[k]F-quinone与mono-NB[k]F-quinone，我们推测以上产物是相应的一级非均相反 应产物B[b]F-quinone, B[k]F-quinone, mono-NB[b]F和mono-NB[k]F与NO3自由基进一步反应的结果。此外，利用混合相对速率法，以异戊二烯作为参比物，计算所得颗粒相 B[b]F 和 B[k]F与NO3自由基非均相反应的有效速率常数分别为(1.2 ± 0.1) × 10-12 和 (5.8 ± 0.3) × 10-13 cm3 molecule-1 s-1, 此外根据球壳模型推算的摄取系数计算公式，NO3自由基在 B[b]F and B[k]F颗粒表面的摄取系数分别为0.22和0.65。相比多环芳烃与NO2及O3的非均相反应速率常数，多环芳烃与NO3自由基非均相反应有效速率常 数大几个数量级。因此，大气夜间环境中，多环芳烃与NO3自由基的非均相反应也许是其最重要的降解途径之一。 （2）利用烟雾箱、真空紫外光电离气溶胶飞行时间质谱仪和最新自主研制的气相飞行时间质谱仪（VUV-TOFGMS）在线研究了大气环境湿度与在气相 [NO3]/[N2O5]比率对颗粒相Fluoranthene (FL)与Pyrene (PY)与NO3自由基的非均相反应的影响，并利用结合GC-MS离线对反应产物分布进行对比分析。研究结果显示降低环境湿度和提高 [NO3]/[N2O5]比率本质是提高了颗粒表面的[NO3(g)]/[NO2+(aq)]比率。因此我们推断大气溶胶颗粒表面的[NO3(g)] /[NO2+(aq)]比率能够明显影响荧蒽和芘的非均相反应降解过程。在实际大气环境湿度和气相[NO3]/[N2O5]比率条件下，颗粒表面较低的 [NO3(g)]/[NO2+(aq)]比率明显抑制NO3自由基初始加成机制。这或许可以解释为什么仅仅1-,3-,7-,8-NFL和1-NPY在荧 蒽和芘与N2O5/NO3/NO2非均相反应中生成而2-NFL和2-NPY却没有观察到。 （3）利用烟雾箱、真空紫外光电离气溶胶飞行时间质谱仪及气相质谱仪在线研究了颗粒表面有效反应位点堵塞现象对芘的非均相化学降解机制的影响。通过对照试 验和浓度对比试验，对不同实验条件下NPY产物的分布进行了对比分析。实验结果显示：NO3初始加成反应和N2O5初始亲电硝基取代反应在气溶胶颗粒的非 均相降解中是共存竞争的。PY非均相反应降解反应与NOx浓度有明显相关性。因此我们推测大气NOx的浓度差异造成的多环芳烃气溶胶颗粒表面的反应位点堵 塞现象可能普遍存在，且对芘的非均相反应降解机制有明显的影响。 |
| 英文摘要 | Polycyclic aromatic hydrocarbons (PAHs) are typical organic pollutants with mutagenic and carcinogenic properties in the atmosphere, and most of their emissions are anthropogenic. The transportation and transforamtion of these pollutants in the atmosphere can directly affect the atmospheric environment and human health. In this study, the heterogeneous reactions of PAHs with N2O5/NO3/NO2 radicals are investigated. The reaction products, mechanisms, and reactive rate constants are obtained in the experiments. The results can shed light on understanding their atmospheric behaviors and potential harms. The detailed findings are shown as follows. (1) The heterogeneous reaction of suspended benzo[b]fluoranthene (B[b]F) and benzo[k]fluoranthene(B[k]F) particles with NO3 radicals are investigated using a smoke chamber, a real-time vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS), and an online atmospheric gas analysis mass spectrometer. There are 9 mono-NB[b]F isomers (retention time at 49.57, 50.60, 51.42, 51.68, 52.23, 52.33, 52.62, 53.06, and 54.07 min, respectively), two di-NB[b]F isomers (retention time at 55.6 and 56.1 min, respectively), 4 mono-NB[k]F isomers (retention time at 50.0, 51.4, 52.2, and 53.4 min, respectively) and 1 di-NB[b]F isomer (retention time at 59.5 min) are observed with GC-MS. 7-，Four different mono- NB[k]F isomers and di-NB[k]F are 7-, 1-，8-，3-NO2-NB[k]F and 3,7-NO2- B[k]F, respectively. Other products observed using VUV-ATOFMS only, such as tri- NB[b]F, mono-NB[b]F-quinone, di-NB[b]F-quinone, B[k]F-quinone, mono-NB[k]F-quinone, are formed in further nitration of B[b]F-quinone, B[k]F-quinone, mono-NB[b]F and mono-NB[k]F. Using a mixed-phase relative rate method, the effective rate constants of PAHs in the reaction with NO3 radicals is determined with isoprene as reference compounds. Under the experimental conditions, the obtained reaction rate constant are (1.2 ± 0.1) × 10-12 和 (5.8 ± 0.3) × 10-13 cm3 molecule-1 s-1, respectively. In addition, the NO3 uptake coefficients on B[b]F and B[k]F particulate are calculated to be 0.22 and 0.65, respectively. According to the effective rate constants obtained in this work and previous data, the heterogeneous reaction rates of PAHs with NO3 radicals are about 4?5 orders of magnitude slower than O3, NO2, and N2O5. Therefore, the results indicate that NO3 radicals play a significant role in chemical transformation of particulate B[b]F and B[k]F in the atmosphere. (2) Effects of Humidity and [NO3]/[N2O5] Ratio on the Heterogeneous Reaction of Fluoranthene and Pyrene with N2O5/NO3/NO2 are investigated using a smoke chamber and an online VUV-ATOFMS and VUV-GTOFMS. The reaction products observed with the VUV-ATOFMS are identified according to GC-MS analysis of the products. The experimental results shows that decreasing the humidity or increasing the [NO3]/[N2O5] ratio in the reaction essentially increases the concentration radio of [NO3(g)]/[NO2+(aq)] on the particle surface (NO2+ is derived from the ionization of N2O5). Thus, it can be concluded that under different atmospheric conditions, the change of [NO3(g)]/[NO2+(aq)] in the particle surface has an influence on the product distribution of FL and PY in the atmosphere. Under these conditions, the concentration ratio of [NO3(g)]/[NO2+(aq)] on the particle surface would be much lower than those in our experiments, which apparently suppresses the NO3 radical-initiated heterogeneous reactions and promotes the . This might explain why 2-NFL and 2-NPY are hardly observed in the heterogeneous reactions of atmospheric particles and why 1-, 3-, 7-, 8-NFL and 1-NPY are observed as the dominant nitro-products. (3) Effect of the Blocking Sites Phenomenon on the Heterogeneous Reaction of Pyrene with N2O5/NO3/NO2 are investigated using a smoke chamber, a real-time VUV-ATOFMS, and an online atmospheric gas analysis mass spectrometer. Nitropyrene isomers observed with the VUV-ATOFMS are identified and analysised by GC-MS. Our results show that the N2O5-initiated ionic electrophilic nitration mechanism and the NO3 radical-initiated mechanism may coexist in atmospheric heterogeneous processes. The phenomenon of blocking reaction sites resulting from different NOx concentration may be ubiquitous on the surface of atmospheric aerosol particles and has a significant impact on the heterogeneous reactions of PY and N2O5/NO3/NO2. We also found that the operative reaction mechanism strongly depends on the concentrations of the nitric oxides in the atmosphere. |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/34468]  |
| 专题 | 生态环境研究中心_大气环境科学实验室 |
| 推荐引用方式 GB/T 7714 | 张鹏. 大气中颗粒相多环芳烃与N2O5/NO3/NO2的非均相化学反应研究[D]. 北京. 中国科学院研究生院. 2015. |
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