Characterization And Sources Of Volatile Organic Compounds In Atmospheric Environment, Taiyuan

The atmospheric pollution of Volatile Organic Compounds(VOCs) was increasingly being concerned. VOCs had been found to be the precursors of zone and secondary organic aerosols, and hadharmful effects on ecology and human health. Taiyuan is one of the heavily industrialized and most polluted cities in China, but the investigation of VOCs in Taiyuan is few. A field sampling campaign during 2014-2015 was conducted for VOCs measurement. Canisters were used to collect ambient VOCs samples. 47 of VOCs were detected, and in the result their ambient levels and seasonal and diurnal trends were reported. Then the photochemical reactivity, ozone formation potentials(OFPs) and sources was estimated and analyzed by some related modes, which is useful to understand the ambient concentrations of VOCs and their effects on environment and human. The sources apportionment will be useful and important in establishing the pollution control measures in Taiyuan. The primary results were as followed:1. The total mass concentrations of 46 VOC species varied from 25.51 to 495.14 ?g/m3. Alkanes were the most abundant species of the VOCs with a share of 49%, followed by aromatic hydrocarbons(40%) and alkenes(8%). Among VOCs, m/p-xylene, benzene and propane exhibited the highest concentrations at 7.96 ?g/m3, 6.24 ?g/m3 and 5.68 ?g/m3 respectively. Ambient concentrations of VOCs in Taiyuan are higher than that in other cities.2. The average concentrations of total VOCs was higher in day than at night, which might be related to their increased release with traffic emissions, and weakened dilution with temperature inversion in morning and night. VOCs concentrations were highest in winter(74.76 ?g/m3), followed by autumn(71.08 ?g/m3), spring(70.68 ?g/m3) and summer(62.21 ?g/m3), but variation trend was slight. Most hydrocarbons, i.e. ethene, propene, n-butane and i-butane, showed higher autumn-winter concentrations than their spring-summer ones.3. Based on the results of propylene-equivalent concentrations and maximum OFPs, alkenes were the highest and accounted for 41% of the total VOCs, followed by aromatic hydrocarbons(30%) and alkanes(29%). The xlyene, ethane and proprene were the top three compounds. Aromatic hydrocarbons were the most contributors for ozone formation(51%), followed by alkenes(29%) and alkanes(20%) among which m/p-xlyene, ethane, proprene and benzene were the largest contributors.4. Some modes, such as the correlation analysis, principal component analysis(PCA), positive Matrix Factorization(PMF) and air trajectoty model, were used for the VOCs source apportionment. Results suggested that coal combust and coke production, vehicle exhaust, biomass combust, NG/LPG and industrial activities were the major sources of VOCs in Taiyuan. The local sources(coal combust, vehicles emission and industry production), as well as the effects of heavily polluted enterprises in the vicinity of the Taiyuan basin, should be concerned for the air quality improvement in Taiyuan.