| PM2.5, atmospheric particles with an aerodynamic equivalent diameter of 2.5 micrometers or less, plays a key role in earth radiative force, global climate change and human health. Regional haze, which was chractarized by the reduced visibility, was frequently reported aver China in recent years and aroused the worldwide attention. And PM2.5 is exactly identified as the primary pollutant for causing haze. Shandong is located in North China Plain (geographical region), which is one of the most polluted regions in China. In the past decades, certain progress has been made in the research field of levels, compositions and sources of PM2.5 in Shandong Province. However, there remains some problems, including the related researches on PM2.5 were mostly concentrated in urban areas and limited studies focused on organic aerosols. For these crucial issues, field measurements were conducted with mutiple online monitoring technology and off line detection technology in typical areas in Shandong, including regional background site, rural site (downwind of the urban area) and urban site. Chemical compositions of PM2.5 were analyzed and sources of PM2.5 were determined. Characteristics of organic aerosol in PM2.5 and the precursor of secondary organic aerosol (SOA) were emphasized. In addition, atmospheric particle-associated perchlorate and chlorate, which were less studied and harmful to human health, were studied to determine their concentrations and sources.Field study was performed from January 2011 to November 2011 at a background site, the Yellow River Delta National Nature Reserve (YRDNNR) to obtain the concentrations of PM2.5 and its chemical compositions. PMF (Positive Matrix Factorization) receptor model and PSCF (Potential source contribution function) were used to identify the sources of PM2.5. The results indicated YRDNNR suffered serious air pollution. The annual PM2.5 concentration was 78.9 μg m-3 and two-thirds of the daily samples at YRDNNR had PM2.5 concentrations higher than ambient air quality standard (first class standard,35 μg m-3). Concentrations of PM2.5 at YRDNNR exhibited distinct seasonal variation, with higher PM2.5 concentration in summer (92.7 μg m-3) than that in winter (62.5 μg m-3), which was much different from that in urban areas. PM25 mass closure also showed remarkable seasonal variations. In summer, secondary inorganic ions (58.0%) were the dominate fraction and organic matter fraction (13.0%) was small, whereas the proportion of organic matter increased to 40.2% in winter. Positive matrix factorisation (PMF) analysis indicated that secondary sulphate and nitrate (54.3%), biomass burning (15.8%), oil combustion (10.7%), crustal matter (8.3%), motor vehicle emission (5.2%) and nonferrous metal smelting (4.9%) were important sources of PM2.5 at YRDNNR on an annual average. Secondary sulphate and nitrate source was probably related to the atmospheric conversion of the primary pollutants emitted from coal combustion from industry and power plant. Biomass burning contribution to PM2.5 exhibited clear seasonal variation, with higher contribution in winter.To obtain further insights into organic aerosols (or carbonaceous aerosol) and biomass burning impact, field measurements of carbonaceous aerosols (organic carbon, OC, and element carbon, EC) were conducted using semi-continous instruments at Yucheng (YC), a rural receptor site in Shandong during summers in 2013 and 2014. The concentrations of PM2.5-associated OC and EC at YC in summer 2013 were 10.80±6.95μgC m-3 and 2.42±1.35 μgC m-3, respectively; those in summer 2014 were 8.05±4.48 μgC m-3 and 1.51±1.02 μgC m-3, respectively. And the concentration of K+ in 2013 (1.17±1.57 μg m-3) was much higher than that in 2014 (0.13±0.28μg m-3). Carbonaceous species at YC exhibited clear diurnal variation, with the primary peak in the early morning and the secondary peak at night. Lower concentrations of OC and EC were observed during the afternoon hours. Based on PM2.5 mass closure method, OM/OC ratio was calculated as 2.07±0.05, providing a reference to estimate organics in PM2.5 at rural areas in Shandong during summer. Biomass burning was frequently identified during the sampling period. Statistical results indicated around half PM2.5 samples were impacted by biomass burning during the summer in 2013.Case studies revealed about half proportion of OC and EC were attributed to biomass burning during typical biomass burning events. From single-particle analysis, the observed organic coating on K2SO4 particles indicated the formation of secondary organic aerosols (SOA) from the oxidation of precursor volatile organic compounds (VOCs) during the aging of smoke released from biomass burning.VOCs were the key precursors of SOA formation in the atmosphere, thus field study was conducted to determine the characteristics of VOCs at YC during summer, 2014. The concentrations of typical VOCs species at YC, including propane, propene, benzene, toluene, isoprene and acetylene were 1.29,0.78,0.62,0.34,0.38 and 1.78 ppbv, respectively. The VOC speciation results showed that alkanes, alkenes, acetylene, aromatics and isoprene accounted for 54.2%,17.8%,14.2%,10.8% and 3.0%, respectively. The VOCs species at YC showed similar diurnal variation:higher concentrations were observed in the morning and at night, lower concentrations in the afternoon hours. PMF analysis indicated that the possible sources for VOCs in YC were aged VOCs (which was related to long-range transport), gasoline evaporation&LPG (liquid petroleum gas), solvent usage and biogenic emission, with contribution of 39.3%,30.2%,17.0% and 13.5%, respectively. VOCs chemical reactivities were evaluated by ozone formation potential (OFP) and OH loss rate. The total OFP for VOCs at YC was 70.48μg m-3, among which anthropogenic alkenes were the largest contributor (43.1%), followed by aromatics (23.8%). OH loss rate was 2.52 s-1, among which 43.1% and 40.5% of total OH loss rate were attributed to isoprene and anthropogenic alkenes, respectively. Based on a parameterization method, aromatics derived SOA from the gas-phase oxidations with OH radical, especially benzene, toluene, xylene and ethylbenzene, made the greatest contribution to SOA concentration formed from total VOCs, accounting for more than 80%. In addition, isoprene derived SOA was non-negligible at rural areas, like YC.Despite the major components of PM2.5, like secondary inorganic ions, organic carbon and element carbon, the trace components perchlorate and chlorate which were hazardous to human health, were new emerging permanent pollutants and less studied. Thus, field campaign was firstly conducted in Jinan to investigate PM2.5-associated perchlorate (ClO4-) and chlorate (ClO3-) in indoor and ourdoor environment. The concentrations of ClO4- and ClO3- were 4.18 ng m-3 and 2.82 ng m-3, respectively. ClO4- concentration increased up to 173.76 ng m-3 in Spring Festival Eve, whereas ClO3- concentration did not show an obvious increase. The concentrations of ClO4-exhibited significant correlation with Cl- and K+, indicating firework display was an important source of ClO4-.The other sources of ClO4-in Jinan need further research. The indoor concentrations of ClO4- and ClO3 in Jinan were 3.54 ng m-3 and 0.94 ng m-, respectively, and indoor ClO4-concentration elevated to 125.14 ng m-3 in Spring Festival Eve. I/O ratio (mass ratio of indoor/outdoor) of PM2.5 and ClO3-were less thanl, whereas I/O ratio of ClO4-(20% paired indoor-outdoor samples) were larger than 1. Case studies revealed that the occurrence of indoor ClO4- concentrations higher than those found outdoors was a common effect of individual fireworks displays, coupled with meteorological influences and poor indoor diffusion conditions. The exposure risks of perchlorate and chlorate indoors indicated that the potential risk of perchlorate exposure to children during fireworks displays is deserving of concern.The current study obtained precious data set (including some of high time resolution) in background, rural (downwind of urban area) and urban areas in Shandong using multiple technologies, providing new data support for future study and offer a scientific basis of PM2.5 controlling strategies in Shandong. |
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