Measurement of Surface Ozone and its Precursors in Urban and Rural Sites in Beijing

A 4 year time continues measurements of ozone and its precursors including NO, NO2 and CO at an urban and a rural site in Beijing area from January 2005 to December 2008 were analyzed to investigate the seasonal and diurnal variation characters of ozone and its precursors, and to understand the effects of local meteorological conditions. Pronounced seasonal variations of ozone and its precursors were observed in urban area, with the maximum ozone mixing rations appearing in late spring and early summer, minimum appearing in winter. Precursors NO, NO2 and CO show opposite seasonal variation patterns to that of ozone. In rural area, O3, NO and NO2 show similar seasonal variation patterns to that of urban area. While affected by the local natural plants emissions, CO reaches maximum in summer in rural area. Typical polluted cities diurnal variation patterns of ozone and precursors NO, NO2 and CO were observed in urban area, characterized by the peak ozone value appearing at 14:00 and valley during nighttime, precursors showing two peaks related two the morning and evening rushes and reaching valley at ozone peaking time. In rural area, ozone shows similar diurnal pattern, while affected by pollutants transported from upwind urban area, peak value appearing time be delayed by several hours to that of urban area, except in winter. Meteorological conditions, especially boundary layerʹs changing do primary contribution to the diurnal variation of ozone precursors CO and NO2, with the highest mixing ratios appearing during night time and lowest around noon time in rural area. NO appears single peak in dawn coming from HONO decomposed by the sunlight at rural site.