Investigation On Atmospheric Volatile Organic Compounds Of Different Types Of Stations In North China

Volatile Organic Compounds (VOCs) are important gaseous pollutants inatmosphere. Some species of VOCs are harmful to human health and environmentdirectly. Besides that, VOCs can also affect environment, weather and climateindirectely through participating atmospheric photochemical reactions which producesecondary atmospheric pollutants like ozone, PAN, and organic aerosol. In thisresearch, a TD-GC×GC/FID/MS system and the corresponding analytical method wasoptimized and applied to observe the VOCs concentrations at4different kind ofstations representing urban, suburban, rural, and background areas in North China,respectively. Based on an intensive field experiment carried out at the4stationssynchronisticly during June2011, the VOCs compositions and their concentrations, aswell as the diel variations and ozone formation capacities for VOCs species wereinvestigated.As a result,107species of VOCs were characterized including32alkanesbetween C4to C15,13alkenes between C4to C10,18aromatics between C6to C12,15halohydrocarbons between C1to C6, and29OVOCs between C2to C13. Duringthe intensive experiment, the concentrations of total VOCs at the suburban site (84.57ppb) and Beijing urban site (82.27ppb) are similar and both at a high level, followedthe concentration of the rural site (75.25ppb). The TVOCs concentration inShangdianzi background site (49.58ppb) is the lowest one, which is lower about41%,40%, and34%than the suburban site, Beijing urban site and the rural site,respectively. Oxygenated volatile organic compounds (OVOCs) showed the biggestcontribution ratio to TVOCs at the4sites, followed that of alkanes. Theconcentrations of alkenes,halohydrocarbons and aromatics have the property about9%～12%to TVOCs concentrations. Diel variations of VOCs species are differentamong4sites due to their different sources in the different environment. The B/Tvalue of the4sites suggested that BTEX may come from not only the vehicle exhaustemission, but also other sources like the evaporation of liquid gasoline and chemicalreagents, and plant emissions.The estimates of the contribution of VOCs species in ozone photochemicalformation using EPC (equicalent propylene concentations) and MIR (MaximumIncremental Reactivity) indicated that OVOCs and alkenes contribute more than other VOCs species in O₃photochemical formation in the4sites, and then alkanes andaromatics, while halohydrocarbons have the lowest contribution in O₃photochemicalformation. More exactly, the contribution of acetaldehyde, propanal, and1-butene isrelatively big.