| Fine aerosol particle (especially PM2.5-the total particle with aerodynamic equavilent diameter lower than 2.5μm) makes a great contribution urban visibility decrease. Located in core area of Yangtze River Delta, Shanghai is one of the regions with the heaviest haze pollution. Unfortunately, studies of contribution of PM2.5to haze pollution and formation mechanism of haze are still not systemically studied.In this study, PM 2.5 samples were collected continuously for one year at ECUST site. Organic carbon (OC), element carbon (EC), water-soluble ions and organic carbon (WSOC) were analyzed, and their characteristics were discussed. Meanwhile, the atmospheric aerosol scattering coefficient was monitored. The total extinction coefficients were calculated and compared by different methods, and improved estimation method was proposed. Based on relationship between PM2.5 and haze, haze was divided into two types which controlled by external sources and local sources, respectively, according to its generation method, and some warrants were suggested to judge the source of haze.Results showed that the PM2.5 daily-average mass concentrations in the four seasons of 2009 and spring of 2010 were 82.60±45.73μg/m3,54.48±22.18μ.g/m3,101.18±47.27μg/m3, 127.50±53.83μg/m3,76.52±46.42μg/m3, respectively. Winter has the highest concentration while summer has the lowest. The components analysis indicated that the carbonaceous components take 21.2%,27.7%,18.8% and 16.8% of total PM2.5 in different seasons of 2009, respectively; and the ion components take 36.3%,18.3%,15.4% and 22.9% of total PM2.5 in different seasons of 2009, respectively. The OC in summer was the lowest, but OC/PM2.5 in summer was the highest, which suggests that secondary aerosol is the major source of particles in summer. The highest EC was found in fall and char-EC/soot-EC ratio was also high in autumn and winter, which might result from the higher contribution of biomass burning in these two seasons. WSOC (Water soluble organic carbon) was the highest in spring, and lowest in summer and WSOC and OC/EC ratio shows a negative correlation in winter, which implies that WSOC mainly comes from primary sources in winter. SO42-, NO3-and NH4+are the most abundant fraction of water-soluble ions, taking 50.8%,24.8% and 11.3% of total ion concentration, respectively. K+, the indicator of biomass burning, shows a high concentration in spring and winter. K+and SO42- show poor correlation in spring, but a better correlation in autumn and winter. This suggests that biomass burning has a higher contribution to particles in autumn and winter, while the sources of particle are quite complicated in spring.Volatile Particulate Organic Carbon (VPOC) and Non-Volatile Particulate Organic Carbon (NVPOC) were defined herein the paper. It was found that the VPOC/OC ratio changed little in different seasons while WSOC showed a negative correlation toVPOC/OC, which suggests that NVPOC may be the major contributor to WSOC. Atmosphere total extinction coefficient was calculated by Koschmieder’s empirical equation and the improved IMPROVE protocol, respectively. The results showed that the former result is higher and the latter is lower than scattering coefficients. The underconsideration of f (RH) of WSOC might be a reason.The sources of haze were classified to external sources and local sources according to the chemical composition of PM2.5. The external sources of haze include transportation of biomass burning and transportation of common pollutants. The local sources of haze are divided into weather-control type and human-activity-control type. The judge theory for haze was discussed according to PM2.5 composition and weather condition in different haze pollution. |
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