Characteristics of observed trace gaseous pollutants in the Yangtze Delta

Six stations in the Yangtze Delta were set up to measure minute-average ground-level concentrations of NO, NOx, SO2, CO and O3 from May, 1999 to Oct., 2000 continually. The percentage of total valid data of all sites was over 80%. The observed data were of adequate regional representation. The individual mean value of NO, NOx, SO2 and CO in the six selected sites was much higher than that of background level. Strong seasonal variations of observed data in the sites were expounded with peaks in winter. These showed that the air had been contaminated by anthropogenic pollutants. The highest monthly mixing ratios of O3 were found in May or June, and an ozone episode in September.Department of Civil and Environmental Engineerin