珠江三角洲一次典型复合型污染过程的模拟研究

Simulation of a typical complex pollution process over Pearl River Delta area

利用空气质量模式系统（MM5-CAMQ-SMOKE）,模拟珠江三角洲一次典型的复合型污染过程,研究O3、NOx及能见度等的时空变化,分析各种气溶胶的质量比例以及对消光的贡献.从模拟结果来看,模式系统能很好的模拟此次过程中光化学烟雾标识物的时空分布,以及灰霾的发生、减弱再到进一步加剧的过程.PM2.5占PM10的质量浓度份额平均为79.8%.爱根核和积聚核的数浓度比巨核数浓度平均高3~4个数量级.在气溶胶质量权重中,硫酸盐所占的比重最高,占PM2.5权重达到31%,元素碳为21%,有机碳为14%,铵盐为7.2%,硝酸盐为2%.在平均相对湿度下,二次气溶胶对消光的贡献超过50%,而在高相对湿度的情况下,二次气溶胶对消光的贡献超过70%.可见此次珠江三角洲地区能见度恶化主要是由各种化学过程生成的细粒子引起.

This paper investigated the temporal and spatial variation of O3,NOx and visibility,and further analyzed the share of mass and the extinction contribution of each aerosol species,based on the simulation of a typical complex pollution process over Pearl River Delta area through the air quality modeling system（MM5-CAMQ-SMOKE）.The spatial and temporal distribution of photochemical smog markers,as well as processes of haze initiating,weakening,and intensifying,could be well simulated by this modeling system.The PM2.5 contributed 79.8% of the PM10 mass concentration.The number concentration of nuclei of aitken mode and accumulation mode was higher than that of the coarse mode on the order of 103~104.Of all the aerosol masses,the sulfate contributed the highest fraction（31%） of the PM2.5 concentration,while black carbon,organic carbon,ammonium,and nitrate contributed 21%,14%,7.2% and 2%,respectively.The extinction contribution of secondary aerosol was more than 50% under averaged relative humidity condition,and more than 70% under high relative humidity condition.Therefore,visibility deterioration in this case was mainly caused by fine particles generated during various chemical processes over the Pearl River Delta region.