Pollution Characteristics Of Organic Compounds In PM_2.5 During2013CAREBEUING-NCP Campaign In A Typical Urban Area Of Beijing

Atmospheric fine particles (PM2.5) samples were collected in typical urban area ofBeijing during the2013CAREBEIJING-NCP observation. N-alkanes, PAHs, fatty acid, etal. organic compounds in PM2.5were determined by using GC-MS technique. The influenceof the long-range transport of air pollutants on the distribution characteristics of organiccompounds in PM2.5was investigated on the basis of the studies on the ambient level,distribution characteristics and sources identification combined with the backward trajectoryanalysis.The results show that the range of mass concentration of PM2.5was from29.73to275.30μg/m3, with an average of157.55μg/m3. There were only two days’ concentration ofPM2.5reached the air quality standard (GB3095-2012) requirements, so the pollution of PM2.5in typical urban area of Beijing during observation was serious. The daily concentration oforganic compounds in PM2.5ranged from784.35to3175.20ng/m3, and its average was1642.09ng/m3. Aromatic acid content was the highest, followed by fatty acid and sugars, andthe n-akanes, PAHs and hopane were low. Organic compounds pollution level at night wasmore seriously than that during the daytime. Meteorological factor has certain influence onthe concentration of organic compounds in PM2.5.The mass concentration of total n-alkanes in PM2.5ranged from50.33to143.49ng/m3,with an average of80.52ng/m3, and the pollution level of n-alkanes at night was moreseriously. Carbon number of n-alkanes was C14~C36, and the Carbon number distributionpresented two kinds of peak shape that are unimodal type and bimodal type. The CmaxwasC29or C31. The values of the ratio of ρ (nC14~nC24) and ρ (nC25~nC36)(LMW/HMW) rangedfrom0.10to0.31, and high carbon number n-alkanes were preferred. The hopane compoundsmass concentration were from2.52to7.53ng/m3, average concentration was4.02ng/m3, andthe concentration at night was more than that in day.17α-21β hopane mass concentration washighest, followed by17α-21β-30norhopane.The saturated hydrocarbon in PM2.5during theobservation period mainly came from the incomplete combustion of fossil fuels and biomass,the emissions of higher plants waxes, phytoplankton, algae and other aquatic plants, theabrasion of tire and road asphalt.The mass concentration of total PAHs in PM2.5ranged from8.94to114.22ng/m3, with an average of24.44ng/m3, and the pollution level of n-alkanes in the day was more seriously.The range of the concentration of B[a] P was from0.06to2.18ng/m3, and the averahe was0.65ng/m3.(4+5) ring PAHs were dominating, followed by (6+7) ring, and3ring PAHs wereminimum. PAHs in PM2.5mainly came from the mixed sources of the incomplete combustionof fossil fuels (motor vehicle exhaust), biomass, and family cook. As the motor vehicleexhaust emission of polycyclic aromatic hydrocarbons, which are mainly composed of dieselexhaust emissions.The new input of pollutants in day was obviously higher than that at night,and the pollutants at night was mixed with the day pollutants after light degradation.The mass concentration of total fatty acids in PM2.5was from307.67to820.03ng/m3,with an average of499.04ng/m3. The pollution level of fatty acids at night was more seriously.The concentration of F16:0and F18:0were higher than other fatty acids. Carbon number offatty acids was from F9:0to F32:0and the Cmaxwas C16or C18. The even carbon number fattyacids was preferred. The concentration of total aromatic acid in PM2.5ranged from156.29to1663.71ng/m3, and its average was627.99ng/m3. The concentration at night was higher thanday. P-phthalic acid was higher than o-phthalic acid, m-phthalic acid was lowest. The organicacids in PM2.5during the observation period came from the the incomplete combustion offossil fuels, secondary resouces, family cook, higher plants emissions. There were new inputpollutants both in day and night, and it was obvious in day.The mass concentration of sugar compounds ranged from87.95to1784.56ng/m3, withan average of451.27ng/m3. Concentrations in day were significantly lower than that duringthe night. Carbohydrate compounds were mainly divided into dehydrated, monosaccharide&disaccharide sugar and sugar alcohols. Levoglucosan was the highest, and the second wasglucose. The sources of sugars were mainly from the combustion of biomass, and thedegradation of microbial.The air mass mainly came from south, and followed by southeast coast and the mid-west Inner Mongolia direction. Different directions air mass transmission had influence onthe ambient level, composition and sources of PM2.5and organic compounds in PM2.5. Inspecific season, the distribution characteristics of oganic compounds in PM2.5have certainindicative significance for the sources of air masses, however the universal remains to befurther studied in the future.