生物质燃烧产生的甲氧基苯酚形成二次有机气溶胶的理论研究

Methoxyphenols are major components in the smoke of biomass combustion emissions. They usually show high reactivity, and can participate in extensive atmospheric chemical reactions, which could generate secondary organic aerosol and other pollutants, further affect human health and cause the regional environmental air quality deterioration. This project will select typical methoxyphenols of the atmosphere, such as guaiacol, syringol, creosol and their derivatives as the main research objects. The formation mechanism of secondary organic aerosol from the atmospheric oxidant OH, O3 and NOx with methoxyphenols will be studied by using high-accuracy quantum chemical calculations and molecular simulation. The formation routes, intermediates and relevant thermodynamical parameters will be investigated. The dominant formation pathways and the rate-determining step will be obtained from this research. The rate constants of the elementary reactions involved in the formation of secondary organic aerosols will be calculated with the aid of the direct dynamical methods. This project will clarify the influence of atmospheric oxidants and the substituent groups on the reactivity of methoxyphenols. A second motivation for this work is to assess the similarities and differences for the formation of secondary organic aerosol form heterogeneous formation mechanism on particles surface and the gas phase reaction mechanism. Establish the prediction model for the formation mechanism of secondary organic aerosol under the condition of biomass combustion. We expect that this research can provide a strong theoretical basis and technological support for not only the effective control of secondary organic aerosol pollution and atmospheric haze pollution, but also the environmental legislation and environmental planning.

甲氧基苯酚是生物质燃烧过程中释放烟气的主要成分，反应活性较高，可参与广泛的大气化学反应，并生成二次有机气溶胶等污染物，影响人体健康及造成区域环境空气质量恶化。本项目拟选取大气中的典型甲氧基苯酚，如愈创木酚、紫丁香醇、木焦油醇及其衍生物等作为研究对象，采用高精度量子化学计算和分子模拟方法研究它们在OH、O3、NOx等氧化剂作用下形成二次有机气溶胶的微观机理。探讨形成路径、中间产物以及相应的热力学性质；找到主要反应通道、速控步骤；采用直接动力学方法计算二次有机气溶胶形成过程中包含的基元反应的速率常数；阐明大气氧化剂及取代基结构对甲氧基苯酚反应活性的影响；总结反应规律，比较颗粒物表面二次有机气溶胶的非均相形成机理与气相反应的异同，建立生物质燃烧条件下二次有机气溶胶形成机制的预测模型，为有效控制二次有机气溶胶污染，进而有效控制环境空气污染以及治理大气污染和环境立法、环境规划提供理论依据和科技支撑。

本项目选取生物质燃烧产生的典型甲氧基苯酚化合物如愈创木酚、紫丁香醇、木焦油醇及其衍生物如香豆醇、丁子香酚等作为研究对象，系统地研究了它们在大气中氧化生成二次有机气溶胶的反应机理。比较了不同氧化剂如OH、O3作用下反应机理的不同，阐明了不同取代基结构对甲氧基苯酚反应活性的影响。主要结论如下：（1）OH自由基引发的甲氧基苯酚的大气氧化机理包括OH加成和H抽提，加成反应优于抽提反应，支链双键加成优于苯环双键加成，主要产物有邻苯二酚、乙醛酸甲酯、丙二醛、高氧化合物(O≥5)和几种羰基或羧基化合物。在高NOx条件下，可与NO2反应生成硝基-甲氧基苯酚化合物。（2）O3分子引发的甲氧基苯酚的大气氧化机理为O3加成形成初级臭氧化物，然后环裂解生成Criegee中间体。类似地臭氧的支链双键加成优于苯环双键加成。（3）OH自由基引发的氧化反应大气寿命较短，大约在3~5小时，远低于臭氧引发的同类化合物大气寿命。这些结果有助于更好地了解生物质燃烧烟气在大气环境中的反应活性和降解规律，为有效控制二次有机气溶胶污染，进而有效控制环境空气污染提供了重要的理论指导意义。