珠江三角洲PM2.5和O3复合污染过程的数值模拟

摘要

WRF-Chem model was used to analyze the characteristics and formation mechanism of a pollution episode with high concentrations of PM2.5 and O3 over the Pearl River Delta (PRD) region on October 27, 2014. It was found that the stable weather condition which was favorable for the accumulation of air pollutants occurred over the PRD region because of a high-pressure ridge in 850hPa height and a high-pressure system in the ground. The western PRD regions, including southern Zhaoqing, Foshan and northern Jiangmen, were the most polluted areas due to the easterly prevailing winds. The high O3 concentrations in southern Zhaoqing and northern Jiangmen were associated with gas phase photochemistry, while the high O3 levels in Foshan were related to physical processes. Photochemical O3 formation in areas with high O3 levels was VOCs-limited, and VOCs transported from urban centers and biogenic VOCs from local emissions in Jiangmen was conducive to photochemical O3 formation. On the other hand, the high concentration of PM2.5 was related to its high initial concentrations, as well as the high production rates of secondary inorganic aerosol (i.e., sulfates and nitrates) through the oxidation of SO2 and NO2. The increment for the concentrations of sulfates and nitrates were mainly related to local generation and regional transport, respectively.%利用WRF-Chem模式对2014年10月27日珠江三角洲一次高浓度PM2.5与O3复合污染过程的特征和形成机理进行数值模拟研究.污染发生时,珠三角受中高层高压脊和低层高压系统搭配形成的静稳天气控制,扩散条件不利.在地面偏东风影响下,主要的污染区域为珠三角西部地区(包括肇庆南部、佛山以及江门北部).数值模式的结果表明,肇庆南部和江门北部的高臭氧浓度源自气相化学过程,佛山的高臭氧浓度则来源于物理过程.高臭氧浓度区属于VOCs控制区,中心城区输送的人为源VOCs和江门本地排放的生物源VOCs促进了臭氧生成.高PM2.5浓度是由较高的起始浓度加上SO2和NO2的高转化率使二次无机盐大量生成造成的,其中硫酸盐浓度的增长主要来自局地生成,而硝酸盐浓度的升高则受区域输送影响较大.