Study On Sources Apportionment Of Inhalable Particle In City And Formation Of Secondary Organic Aerosol

Inhalable particle (PM10) now has become the primary pollutant in urban air environment. As an important economic city in Jiangsu province, the air pollution in Xuzhou is serious. In order to improve and enhance the air quality in the city, chemical mass balance (CMB) was applied to calculate the source aportionment of PM10and acquire the contribution value and rate of each source. Tunnel test was utilized to determine the emission factors for PM10and particle-phase polycyclic aromatic hydrocarbons (PAHs) from real-world vehicle, final chamber system was used to simulate the formation of secondary organic aerosol (SOA), different ratios of precursors were changed to analysis the characteristic of SOA. It has an contribution for PM10pollution reduction through reasonable plannation and designation of street canyon layout.(1) The source apportionment and characteristics of spatial and temporal variation of PM10were investigated in Xuzhou. Results show that the PM10pollution in Xuzhou is serious, whose annual average concentration is4times higher than the Grade II national standards for air quality, and2times higher than the PM10concentration in Nanjing. The samples of six sources were analyzed, such as soil dust, coal combustion dust, smelting dust, construction dust, motor vehicle exhaust and urban dust. PM10samples were collected at different functional aeras in Xuzhou, and CMB model was utilized to determine the source apportionment of each source. Results show that the main source is the urban dust, whose value and rate are95μg/m3and33.6%, respectively. Sulfate is the second, which contributes to49.6μg/m3and17.6%. Motor vehicle exhaust contributes to39.6μg/m3and14%. Construction dust contributes to28.5μg/m3and10.1%. Nitrate contributes to27.7μg/m3and9.8%. Coal combustion contributes to19.8μg/m3and7%. Smelting dust contributes to4.5μg/m3and1.6%. Furthermore, dust, as a mixed source, should receive more attentions.(2) Investigating on the vehicle exhaust pollution in city, Fu Gui-shan tunnel was chose for field monitoring, including traffic volume, composition, meteorological data and other parameters, the principle of mass balance was used to calculate the emission factors of different vehicle. Results show that the emission factor for PM10and PAHs is687mg/(veh·km) and18.853mg/(veh·km) in summer,714mg/(veh·km) and20.374mg/(veh·km) in winter. SPSS was utilized for weight analysis to acquire emission factors of different vehicles, and the estimation for PM10emission factor of gasoline-fueled vehicles (GV) is513mg/(veh·km). But the value for diesel-fueled vehicles (DV)(914mg/(veh·km)) is two times than GV. While emission factor of DV for PAHs (31.290mg/(veh·km)) is nearly4times higher than emission factor of GV(9.310mg/(veh·km)). The emission factors for benzo[a]pyrene of DV (3425μg/(veh·km)) and GV(872μg/(veh·km)) are still much higher than European countries.(3) The effect of nitric oxide (NO) concentration on secondary organic aerosol (SOA) formation during ozonolysis of a-pinene has been studied in a stainless steel chamber system that simulates the indoor environment. Three sets of experiments with different concentration ratios of NO/O3were conducted in this study. For the NO/O3ratio of0.5, nitrate radical was found yielding the maximum SOA concentration (31.85u.g/m3), the SOA yield was the highest at22%of a-pinene used in the experiment. When the NO/O3ratio is2, the minumum SOA concentration (8.68μg/m3) was found, and the concentration of reactive oxygen species (ROS) was the highest value (6.52nmol/m3). When NO/O3is equal to1, the highest density of SOA (1.51g/cm3) is found. According to a-pinene ozonolysis, the system without-OH scavenger is expected to be from reactions with both ozone and hydroxyl radicals, and the concentrations of·OH is1.4-8.5X10-5ppb, which is depended on the concentration of O3at steady-state. With more·OH presenting, a higher percentage of semi-volatile species are reacted in the gas phase reducing the amount that can partition into the condensed phase.(4) The effect of nitric oxide (NO) concentration on secondary organic aerosol (SOA) formation during ozonolysis of d-limonene has been studied in a stainless steel chamber system that simulates the indoor environment. The different combinations of NOx and O3were conducted in the system to calculate the change of SOA mass concentration, SOA density, ROS concentration and intensity. Results show that the maximum SOA mass concontration (157.3μg/m3) is found at the NO/O3ratio of0.5, and the SOA number concontration (7853#/cm3) is the highest. When NO/O3is equal to1, the ROS concentration was the highest in all experiments, higher SOA mass concerntraion lead to higher SOA yield and higher ROS concerntration, while lower SOA mass concerntration leads to lower SOA yield and lower ROS concentration.