Characterization of submicron aerosols in the urban outflow of the central Pearl River Delta region of China

Submicron aerosol particles （with aerody- namic diameters less than 1 pm, PM1） were sampled and measured in Heshan, an urban outflow site of Guangzhou megacity in Pearl River Delta in South China, using an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer （HR-ToF-AMS） in November 2010 during 2010 Guangzhou Asian Games. The mean PM~ mass concentration measured was 47.9 ± 17.0 μg.m3 during the campaign, with organic aerosol （OA） and sulfate being the two dominant species, accounting for 36.3% and 20.9% of the total mass, respectively, followed by black carbon （17.1%, measured by an aethalometer）, nitrate （12.9%）, ammonium （9.6%） and chloride （3.1%）. The average size distributions of the species （except black carbon） were dominated by an accumulation mode peaking at -550 nm. Calculations based on high-resolution organic mass spectrum showed that, C, H, O and N on average contributed 58.1%, 7.3%, 30.7%, and 3.9% to the total organic mass, respectively. The average ratio of organic mass over organic carbon mass （OM/OC） was 1.73 ± 0.08. Four components of OA were identified by the Positive Matrix Factorization （PMF） analysis, including a hydro- carbon-like （HOA）, a biomass burning （BBOA） and two oxygenated （SV-OOA and LV-OOA） organic aerosol components, which on average accounted for 18.0%, 14.3%, 28.8% and 38.9% of the total organic mass, respectively.

Source apportionment of PM_(2.5)light extinction in an urban atmosphere in China

Haze in China is primarily caused by high pollution of atmospheric fine particulates（PM2.5）.However, the detailed source structures of PM2.5 light extinction have not been well established, especially for the roles of various organic aerosols, which makes haze management lack specified targets. This study obtained the mass concentrations of the chemical compositions and the light extinction coefficients of fine particles in the winter in Dongguan, Guangdong Province, using high time resolution aerosol observation instruments. We combined the positive matrix factor（PMF） analysis model of organic aerosols and the multiple linear regression method to establish a quantitative relationship model between the main chemical components, in particular the different sources of organic aerosols and the extinction coefficients of fine particles with a high goodness of fit（R^2= 0.953）. The results show that the contribution rates of ammonium sulphate,ammonium nitrate, biomass burning organic aerosol（BBOA）, secondary organic aerosol（SOA） and black carbon（BC） were 48.1%, 20.7%, 15.0%, 10.6%, and 5.6%, respectively. It can be seen that the contribution of the secondary aerosols is much higher than that of the primary aerosols（79.4% versus 20.6%） and are a major factor in the visibility decline. BBOA is found to have a high visibility destroying potential, with a high mass extinction coefficient, and was the largest contributor during some high pollution periods. A more detailed analysis indicates that the contribution of the enhanced absorption caused by BC mixing state was approximately 37.7% of the total particle absorption and should not be neglected.