RESUMO
Accurate identification and rapid analysis of PM2.5 sources and formation mechanisms are essential to mitigate PM2.5 pollution. However, studies were limited in developing a method to apportion sources to the total PM2.5 mass in real-time. In this study, we developed a real-time source apportionment method based on chemical mass balance (CMB) modeling and a mass-closure PM2.5 composition online monitoring system in Shenzhen, China. Results showed that secondary sulfate, secondary organic aerosol (SOA), vehicle emissions and secondary nitrate were the four major PM2.5 sources during autumn 2019 in Shenzhen, together contributed 76 % of PM2.5 mass. The novel method was verified by comparing with other source apportionment methods, including offline filter analysis, aerosol mass spectrometry, and carbon isotopic analysis. The comparison of these methods showed that the new real-time method obtained results generally consistent with the others, and the differences were interpretable and implicative. SOA and vehicle emissions were the major PM2.5 and OA contributors by all methods. Further investigation on the OA sources indicated that vehicle emissions were not only the main source of primary organic aerosol (POA), but also the main contributor to SOA by rapid aging of the exhaust in the atmosphere. Our results demonstrated the great potential of the new real-time source apportionment method for aerosol pollution control and deep understandings on emission sources.
RESUMO
To investigate the effect of meteorological characteristics on PM2.5 chemical composition and the spatial distribution of different PM2.5 species in Shenzhen, 24-h PM2.5 samples were collected every six days from December 2008 to December 2009. The sampling network included an industrial site at Baoan, an urban site at Luohu and a seaside site at Yantian. Water-soluble inorganic ions and carbonaceous material (organic carbon and elemental carbon) were analyzed. The industrial site showed a much higher concentration than that of other two sites of organic matter, elemental carbon and nitrate, which presented the obvious difference of local emissions. But for the concentration of sulfate and ammonium of three different sites nearly stayed at the same level and indicated that they were mainly influenced by regional transport. OC/EC had the characteristics of the industrial site < the urban site < the seaside site, which implied that the industrial site had less secondary organic matter and more primary pollution sources. As the subtropical maritime monsoon climate is the dominant meteorological feature of the Pearl River Delta with a southwesterly transport and abundant rain in spring and summer, in contrast to a northwesterly transport and little rain in fall and winter, the PM2.5 pollution was much more serious in winter than in summer. Compared with the results of the similar experiment in 2004, the concentration of sulfate in PM2.5 has significantly declined because of the measures of reducing the emission of sulfer dioxide. But the pollution of vehicle emissions has become significant.