Analysis Of Fine Particle’s Chemical Characteristics And Secondary Pollution Formation At Heshan Atmospheric Supersite

In recent years, the Pearl River Delta(PRD) was in the influence of combining primary and secondary pollution which had caused high oxidated capacity and fine particle concentration. The O3 and PM2.5 became the mainly primary atmospheric pollutants. In this study, the Heshan atmosphere super station was selected to conduct our measurement. And we mainly focused on physicochemical characteristics of the single particle aerosol in the days with O3 and PM2.5 be the mainly primary atmospheric pollutants and the sources of carbonaceous, also the causes of secondary pollution during a typical Complex Pollution Episode. The chief conclusion were as follow:1) Carbon-containing particles represented more than 70% of all the detected particles which was the main particles in PRD. On the whole, secondary species were more preference to mixing with carbon-containing particles. While, non-carbon-containing particles were more preference to mixing with nitrate. Influenced by different regional air mass and meteorological conditions, carbon-containing particles were mainly mixed with ammonium sulfate in summer. And there were more secondary species in single particle and better mixing state in autumn than in summer. When under different primary pollutants and different levels of pollution, the mixed degree of nitrate and ammonium and secondary organic components with all classes particles were along with the increase of pollution levels.2)In Heshan supersite region, Organic carbon(OC) mass concentration varied between 1.0~14.4μg·m-3, with an average of 6.0±2.8μg·m-3 and element carbon(EC) varied between 0.2~7.9μg·m-3, with an average of 2.4±1.4μg·m-3. Secondary organic carbon(SOC) accountting for about 47.8% of the mass concentration and was the biggest contribution source of OC in fine particle. The second source of OC is motor vehicle exhaust emissions, accounted for about 31.4%. And also is the main source of EC, accountted for about 87.2% of the mass concentration in fine particle. The ratios of OCbb/ECbb and Kbb/EC shows that biomass burning was the mainly source for EC except motor vehicle exhaust emissions. Back trajectory and chemical tracer analysis showed that the value of CO/NOy will be higher when the air mass from Zhaoqing, a city with high polluted regions than that from ocean and way to Hong Kong, Shenzhen and Dongguan. And made secondary specials increase rapidly, also aggravating secondary pollution.3) During the Complex Pollution Episode, aerosol particles were showed to be neutral. And all the secondary specials accounted for about 74% of mass concentration of measured components. The precursor of secondary specials through the liquid phase oxidation reaction on the surface of porous carbonaceous especially element carbon was their main formation mechanism of secondary specials. The high ratio of precursor gases conversion and weather favored the ammonium nitrate’s rapidly formation and accumulation was the primary cause of secondary pollution formed.