| In this paper, atmospheric reactive gases including NOx, SO2, CO and O3 were monitored one year at five sites that are the Gucheng agricultural station, the Beijing urban station, the Shangdianzi background station, Longfengshan background station and Lin'an background station. Based on the observational data, characteristics of the gaseous pollutants at the sites are studied, including seasonal cycles, spectrum distributions, averaged diurnal variations in different seasons and Windroses of pollutant concentrations. On the basis of the above analysis, the ratios of CO/NOx, CO/SO2 and SO2/NOx and their variations are determined using the observational data. The ratios are then compared with emission ratio derived from the emission inventories (INTEX-B, etc). It is found that The ratios were not big changed with seasonal cycles in Gucheng, Beijing, Shangdianzi, Longfengshan and Lin'an stations. The observed concentration ratios of 9.6 for CO/SO2 and 13.1 for CO/NOx are agreed with the emission ratios derived from the emission inventories in Lin'an stations, but at (the) least 50% higher than the emission ratios derived from the emission inventories in Gucheng, Beijing, Shangdianzi and Longfengshan stations. The result shows that CO emission may be underestimated by more than 50% in the emission inventories. For Gucheng, Beijing, Shangdianzi stations, CO emission from biomass combustion, especially the large-scale straw combustion in harvest seasons would be the important but greatly undervalued source in the north China region. The analysis of the observation data of Gucheng station indicates that CO emissions in straw burning periods are (90%±30%) higher than that in other periods, which value greatly exceeds the extra emissions of CO in straw-burning period estimated in the emission inventories. In future, the impacts of emissions from agricultural straw burning on the emission strengths should be given much more concerns in the process of making and using the emission inventories.
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