| Pearl river delta（PRD）was one of the most population city clusters in china. With the fasturbanization and industrialization in recent three decades, the PRD area had been encountered asevere photochemical pollution due to a large amount of ozone precursors (VOCs, NOx, CO)emitted from anthropogenic sources. In order to provide a scientific guideline for the control ofphotochemical pollution in PRD, the VOCs pollution characterization and its impact on EKMAhad been analyzed by VOCs online instrument between urban and rural area in PRD during aperiod of one and a half year.Conclusions had been followed:（1）55VOCs had been detected, including29alkanes,10alkenes and16aromatics, its annualpercentage concentrations were58%,16%and26%respectively. The distribution of VOCsconcentrations was winter>autumn>spring>summer. The diurnal variation of total VOCsappeared to be two peaks. It was no weekend effect during July while it was very apparentduring December; Aromatics and alkenes are two large components for ozone formationpotential in Guangzhou atmosphere. Toluene, m,p-Xylene and1,3,5-Trimethylbenzene were thekey aromatics compounds, which contributed to51.9%ozone formation potential.Meteorological factors and temperature exerted a great effect on VOCs concentration. TheVOCs concentrations were low when the wind directions were NNE, NE and SSW because ofthe high wind speed, which was in contrary with the situation when the wind directions wereWNW and ENE. BTEX and isoprene were dramatically higher in summer than in winter due tothe fact that higher temperature caused higher solvent evaporation and plant emissionrespectively.（2）The diurnal variation of VOCs and NOx had a positive correlation, having two peaks andthe characterization of the same source. The diurnal variation of ozone had an anti-relationshipwith them, appearing only one peak, with the characterizations of lower in spring and winter andhigher in summer and autumn.（3）The annual accumulative daily rate of VOCs/NOXinitial concentration（morning6:00~9:00below4,8,12,16were about12.4%,70.4%,94.1%and98.9%respectively, which accounting forthe fact that the formation of ozone was controlled by VOCs in70.4%days of monitoring. Theformation of ozone was controlled by NOx in July and controlled by VOCs in December.（4）The factors of ozone formation were complicated. When NO2/NO ratio was high, ozoneconcentration would be high. The production of ozone was higher in summer and autumnbecause of temperature. The ozone concentration at sampling was high when the leading winddirections were W, WSW and SW. （5）The EKMAcharacterization represented that VOCs/NOx ratio in spring, summer, autumnand winter was6.1,8.3,7.1,5.4respectively.Ozone concentration production in spring, summer,autumn and winter was40.4ppbv,62.6ppbv,50.8ppbv and24.4ppbv.(6) Reducing the emission of VOCs and NOx at the same time in Guangzhou during spring,autumn and winter would be helping the control for ozone. However，the ozone formation insummer was controlled by VOCs and NOx alternately, The control for ozone should be furtherthinning. |
