DISTRIBUTIONS AND VARIATIONS OF SURFACE OZONE IN CHANGSHU,YANGTZE DELTA REGION

Through one and half year continuous in-situ measurements,the distributions and variationsof surface ozone and its precursors at a typical mixed agricultural and metropolitan area-Changshu,Yangtze Delta region,were studied.The preliminary analysis on the concentrationlevels and variations of surface ozone indicated the obvious seasonal and diurnal cycles during theexperiment.The hourly averaged concentrations of surface ozone were high,in about 17% of totalvalid hours the surface ozone concentration exceeded 50 ppb,and in 22 days the hourly averagedozone concentration was greater than 100 ppb.There were about 40% of the days in that the dailymaximum 8-hour ozone concentration was greater than 50 ppb.The days with daily maximum 8-hour ozone concentration greater than 80 ppb were about 33 days that accounted for about 8% ofthe observational days.The variations of 5-day moving averaged ozone concentrations dependedboth on the weather conditions and on the changes of ozone in background atmosphere.Photochemical process had the significant impacts on ozone productions.