空气质量模式中化学反应机理简化及应用研究

Chemical reaction mechanism is the key components of atmospheric chemistry model. VOCs are the main participants in chemical reaction, but VOCs include different kinds of chemical substances, the chemical active is quite different and related to a mass of reaction. How to represent the chemical reaction mechanism under the time-limited of atmospheric chemistry model is a key problem that is exigent to be solved. This proposed study is based on the MCM near-explicit chemical mechanism, combining with the source emission and composition characteristics in specific region ( Beijing as an example) to apply the method of reducing the emission chemical composition and simplifying degradation reaction mechanism. This study will also use the simulation from the box model to screen the representative and suitable complex chemical model of gas phase chemical reaction mechanism. We emphasize the specific reaction from actual emission instead of using the traditional mechanism. Also, we will combine the simple gas phase chemical reaction and SOA module with CUACE model. We will improve the present CUACE model, and provide the basis for estimate the future air quality and the effective mitigation measures. Moreover, even the big regional difference among population, energy and economy in China, the mechanism developed in this study has broad application.

化学反应机理是大气化学模型的关键组分，VOCs是化学反应的主要参与者，但其种类繁多，活性千差万别，涉及到数以万计的反应，如何在满足大气化学模式时效性的条件下保持化学反应机理的代表性一直以来是大气数值模拟中一个备受关注又亟待解决的问题。本研究以MCM显式化学机理为基准，结合特定地区（以北京为例）源排放和组成特征，采取减少排放物种和简化降解反应的方法，通过盒子模型模拟结果来筛选有代表性的、并适用于复杂化学模式的气相化学反应机理。摒弃了我国以往这方面研究采用传统机理的做法，强调基于实际排放的特定反应。并将简化的气相化学机理耦合到自主研发的化学天气预报模型中，同时耦合SOA模块，改进和完善现有的化学天气预报模式，并为预测未来空气质量及制定行之有效的减排措施提供了手段和依据。同时，鉴于我国人口，能源，经济等不均衡造成的源排放的千差万别，该机理简化方法具有良好的推广应用价值。

人为源和天然源排放的挥发性有机化合物（VOCs）是大气中二次污染物臭氧及二次有机气溶胶（SOA）的重要前体物，本研究以MCM显式化学机理为基准，结合我国VOCs源排放和组成特征，采取减少排放物种和简化降解反应的方法，利用MECCA盒子模式进行了情景实验，以臭氧作为比较对象，筛选了能够满足化学天气预报时效性的气相化学反应机制，并将筛选的气相化学反应机理耦合到grapes_cuace化学天气预报模式中，进行区域大气二次污染物臭氧和二次有机气溶胶的模拟研究。发现，简化化学机制模拟的臭氧与观测结果有很好的可比性；在区域尺度上，有显著的二次有机气溶胶生成，研究时段内其对PM2.5的贡献仅次于硫酸盐，高于铵盐和硝酸盐，对PM2.5的区域平均贡献大约是10%；生物源排放VOCs对SOA的贡献在晚上和植被覆盖率高的地方较大。