A Preliminary Study Of Ambient VOCs Variation And Chemical Reactivity In The Urban Area Of Shanghai, China

The ambient concentration of 56 VOCs species were measured continuously in the urban of Shanghai, China from Jan.1 to Dec.31,2010 by GC-FID instrument. The hourly mixing ratio of ambient VOCs in the urban of Shanghai is (2.47～301.48)×10-9, and the average mixing ratio is (26.45±23.36)×10-9. The major compositions of VOCs were alkane, alkene, aromatic, and acetylene, accounting for 46.72%,33.18%,11.33%, and 8.76% of the total VOCs, respectively. The VOCs monthly average concentration shows "W" type distribution, which the November average concentration is the most high, the September lowest. In different seasons, the main species are very similar, which are C2～C5 alkane,ethylene,ethyne,benzene,xylene, toluene, ethylbenzene and so on. Diurnal variation of TVOC and alkane,alkene is similar. But the aromatic is different, because solvent evaporation effect is big.The ratios of T/B (toluene/benzene) was found at level of 3.51±2.40, indicating that vehicles are not the only source of ambient VOCs, but the others sources, e.g. solvent use, and evaporation of gasoline, and LPG, make large contribution to VOCs as well. And the ratio of E/E(ethane/ethyne) 0.98±0.68 stating that the plume are aged. According to the ratio of E/C (ethyne/CO), the plume is fresh in spring and winter, and photochemical age is relatively long in summer and autumn. The constant of ambient VOCs radical loss rate (KOH) is 8.05×10-12 cm3·molecule-1·s-1 and the maximum O3 incremental reactivity (MIR) is 4.00 mol·mol-1, which state the chemical reactivity of ambient air in urban Shanghai is correspond to ethylene. The mixing ratio and composition of VOCs vary with wind direction and wind speed, since the different location of VOCs emission sources. To the OH radical loss rate (LOH), the alkene and aromatic were the most important contributors, and accounted for 42.21% and 40.83%, respectively. In the case of ozone formation potential (OFP), the alkene and aromatic accounted for 21.70% and 62.75%, respectively. The key reactive species are xylene, toluene, ethylbenzene, ethylene, propylene, trans-2-butene, and isoprene.