| Sea-land and mount-valley circulations are the dominant mesoscale synoptic systemsaffecting the Beijing area. Under the influence of these two circulations, the prevailing windis southwesterly from afternoon to midnight, and then changes to northeasterly till forenoon.This prevailing wind pattern can affect the pollutants' regional distribution significantly.According to the survey on the above meteorological background and regional pollutantsource distribution character, a relatively systematic and intensive field experiment on ozonephotochemical pollution in Beijing area was carried out from June to September2007.Surface ozone and its precursors' concentrations were measured at four stations, which arelocated along the route of prevalent wind. Based on the observed data from field experiment,as well as photochemical box model and3-D regional chemical and transport modelsimulations, the effect of VOCs on the formation of ozone in Beijing area was investigated byclassifying the VOCs progressively (from total VOCs to classified VOCs, and to speciatedVOC). An emission inventory of speciated VOCs emitted from main anthropogenic sources ofBeijing was developed and applied. Main conclusions of this thesis include:①Due to thehigh traffic density and local emissions, the average levels of reactive VOCs at the urban siteswere much higher than those at the SDZ regional background site. Alkanes were the primarycomponents of VOCs in Beijuing area, followed by aromatics, alkenes and biogenic VOCs.Alkanes, alkenes, aromatics and biogenic VOCs all had much higher ambient concentrationsat the urban site than those at the rural site, while the percentage of biogenic VOCs to totalVOCs was higher at the rural site than that at the urban site.②The gross ozone productionrate G(O3) and ozone production efficiency (OPE) have been calculated with a photochemicalbox model constrained by observed data, and the relationship between OPE and NOxconcentration was also analyzed. Results showed that photochemical ozone productionprocess is mainly sensitive to VOCs at urban area. In the background area, the productionprocess is sensitive to VOCs and NOxalternatively.③A3-D regional chemical and transportmodel WRF-Chem was used to simulate the typical regional photochemical pollutionprocesses in Beijing area. Simulated results showed that the ozone formation is controlled bythe alkenes emissions in the urban area. Reducing the emissions of alkenes can decrease O3concentration efficiently in urban area, and this also affects the concentration level of ozone inbackground area.④Alkenes make a major contribution to the LOH, aromatics dominate OFP atboth urban and rural sites. According to the OH loss rate coefficient (LiOH) and the ozoneformation potential (OFP) estimated from the observed ambient mixing ratios of speciatedVOCs, key reactivie species for the ozone formation in Beijing area were recognized. They are m,p-xylene, toluene, trimethyl benzene, propylene, isoprene and butenes. Compared to thethe urban area, biogenic emission and the regional transport have a large influence on OHradicals and the ozone formation in the regional background area.⑤An emission inventoryof speciated VOCs emitted from main anthropogenic sources of Beijing in2003and2006wasdeveloped, and the ozone formation potential (OFP) of VOCs was estimated. Alkenes make amajor contribution to OFP. The top10species, in terms of OFP, consist of ethylene,m,p-xylene, toluene,1-butene, i-pentane, trans-2-butene, propene, cis-2-butene, o-xylene, andacetylene. These species contribute about60%to the total VOC emissions but account for80%of the OFPs in the region. Both high VOC emissions and OFP values appear in the urbanarea of Beijing. Decreasing the traffic exhaust, solvent volatilization and gasoline evaporationwill be the most effective way to reduce VOC emissions and control ozone formation inBeijing area.⑥Local photochemistry played adominant role in ozone formation at urbansite, while biogenic VOCs emissions and long range transportation by urban plume made agreater percentage contribution to OH radical consumption and ozone creation at the ruralsite.
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