Compositional Variations Of Solvent-Extractable Organic Compounds In PM_2.5 And Their Applications In Source Apportionment

The seasonal and diurnal viriations of organic matter in 24h PM2.5 samples and time interval PM2.5 samples in Shanghai were studied in this research. The differences between urban and industrial area in Shanghai was also analyzed. Simultaneously, ratios of homologous compound, CPI and some statistical methods such as PCA,PMF were also applied for source apportionment of organic matter in PM2.5 of Shanghai. We also carried out the statistical analysis of the concentrations of organic matter in PM2.5 and the meteorological parameters. And these methods were applied to the analysis of the organic matter in PM2.5 samples collected in Taizhou, a city with e-waste industry in Zhejiang province in China.Though relatively lower compared with other Chinese cities, the concentration of organic matter in PM2.5 of Shanghai was obviously higher than that of the developed areas in the world such as the US. Alkanes, PAHs, fatty acids and levoglucosan showed obvious seasonal variations of winter>spring>summer. As for Phthalates, the concentration in summer was slightly higher than those in spring and winter. Overall, organic matter in PM2.5 had different seasonal characteristics caused by meteorologic conditions and the seasonal change of emission sources.Concentrations of Alkanes, Hopanes and PAHs in PM2.5 samples from industrial area of Shanghai were obviously higher than those in urban area, indicating more serious atmospheric pollution caused by industrial activities.The diurnal viriations of n-alkanes in different seasons can be roughly divided into three types: the first case, high concentrations of alkanes can be found at night and in the morning caused by low wind speed and obvious stagnant atmospheric condition, and the diurnal variation of pollutant concentrations was huge. The second case occurred when the speed of wind was higher and had obvious diurnal variation with higher wind speed during the day than at night. Then concentrations of alkanes at night and in the morning were higher than those during daytime but the difference was relatively small. Thirdly, the wind speed was high and showed small diurnal variation, then concentrations of alkanes during daytime were usually higher than those at night, reflecting the diurnal changes of emissions intensity.Concentrations of PAHs in PM2.5 also showed obvious diurnal viaiations. The highest PAHs concentration was 5-6.5 times of the lowest concentration in the same sampling day. Generally speaking, the characteristics of the diurnal variation of PAHs was similar with that of n-alkanes. PAHs concentration rose distinctly from early morning (0:00AM-6:20AM) to morning (6:30AM-10:00AM) in all sampling days. In the late autumn and winter sampling days, the highest PAHs levels all occurred in the morning rush hours (6:30AM-10:00AM), indicating the contribution of traffic emissions. The diurnal variation of fatty acids was also mainly controlled by meteorological conditions and similar to that of alkanes. As for levoglucosan, the diurnal variation was not distinct. The diurnal variation of phthalates in spring and summer was consistent with the variation of ambient temperature, but the diurnal variation of phthalates in winter not obvious.Correlation of organic compounds in PM2.5 and meteorological parameters were found. Alkanes, PAHs and fatty acids had negative correlation with temperature and wind speed, and had significant positive correlation with atmospheric pressure, indicating that the concentrations of alkanes and PAHs were controlled to a large extent by temperature and wind speed. A weak positive correlation was found between alkanes concentration and relative humility, while negative correlation between concentrations of PAHs and fatty acids. The correlation between phthalates and meteorological factors was very weak.The results of regression analysis of daily time interval samples showed similar relationship between PAH concentrations and temperature and wind speed as that from daily integrated samples, but moderate positive correlations with relative humidity, which was different from the trend of seasonal variation. Our results suggested that wind speed was the most important factor controlling the diurnal variation of concentrations of PAHs and alkanes, while ambient temperature for the seasonal variations. More significant negative correlations between concentration of PAHs and wind speed (higher R value) were found in days with lower ambient temperature such as winter, late autumn and early spring.The percentage of low molecular weight (LMW) PAHs in total PAHs showed good correlation with wind speed, the lowest contribution of LMW PAHs occurred at the same time interval when the wind speed was the lowest. The variation of emission sources caused by the accumulation of local emitted pollutants should be the major reason for the observed diurnal variations of the LMW and high molecular weight (HMW) PAHsJudged from the diagnostic PAH ratios, PAHs in PM2.5 samples of Zhabei,Xujiahui and Baoshan in different seasons were all from a mixed sources of coal combustion and tail gas from vehicles. As for industrial area, Baoshan, emission characteristics of PAHs from coal combustion was more obvious in winter, while for the urban areas, Zhabei and Xujiahui, mobile emission of PAHs was more important in summer.Positive matrix factorization (PMF) was performed to apportion sources of PM2.5 in Shanghai, and eight factors were identified and they can be assigned to coal combustion (30%), vehicles emissions (10%), secondary nitrates (20%), biomass burning (10%), plant wax emissions (12%), industry (6%), cooking meat(2%), and plastic/waste burning(10%).Our analysis on the organic matter in PM2.5 samples collected in Taizhou showed that the pollution level of airborne organic pollutants was much higher at the e-waste dismantling area than the comparing urban site, indicating severe air pollution caused by the e-waste recycling activities. To achieve better air quality at the e-waste dismantling area, more effort should be put to control the emissions from transportation and kitchen besides regulating the e-waste recycling activities.Much higher concentrations of quterphenyl was found at the e-waste dismantling area than those at the urban area of Taizhou. Quaterphenyl had strong correlation with other PAHs in the e-waste dismantling area, suggesting that it cab be an indicator for the emisson from e-waste dismantling activities.