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Abstract: We present two years (January 2007–December 2008) of atmospheric SO2, NO2 and NH3 measurements from ten background or rural sites in nine provinces in China. The measurements were made on a monthly basis using passive samplers under careful quality control. The results show large geographical and seasonal variations in the concentrations of these gases. The mean SO2 concentration varied from 0.7±0.4ppb at Waliguan on Qinghai Plateau to 67.3±31.1ppb at Kaili in Guizhou province. The mean NO2 concentration ranged from 0.6±0.4ppb at Waliguan to 23.9±6.9ppb at Houma in southern Shanxi. The mean NH3 concentration ranged from 2.8±3.0ppb at Shangdianzi in northeastern Beijing to 13.7±8.4ppb at Houma. At most sites, SO2 and NO2 peaked in winter and reached minima in summer, while NH3 showed maximum values in summer and lower values in cold seasons. On the whole, the geographical distributions of the observed gas concentrations are consistent with those of emissions. The ground measurements of SO2 and NO2 are contrasted to the SCIAMACHY SO2 and OMI NO2 tropospheric columns, respectively. Although the satellite data can capture the main features of emissions and concentrations of SO2, they do not reflect the variations of SO2 in the surface layer. The situation is better for the case of NO2. The OMI NO2 columns capture the geographical differences in the ground NO2 and correlate fairly well with the ground levels of NO2 at six of the ten sites. [Copyright &y& Elsevier]

Ambient O3, NOx, NOy, and CO were measured at the Shangdianzi regional background station from 26 March to 9 October 2008, and VOCs samples were taken and analyzed. This paper uses the data to obtain the ozone production efficiency (OPE) at Shangdianzi and studies the relationship of OPE with NO, and VOCs. In addition, the potential impact from the dry deposition of NOx oxidation products on the calculated OPE was estimated and tentatively corrected. Based on this study, the daily OPE varied in the range of 0.2-21.1, with an average of 4.9 +/- 3.6. An overall OPE average of 4.3 +/- 1.5 can be obtained. The dependence of OPE on the NO, concentration can be described using an empirical parabolic function. If the concentration of NOx is lower than 14 x 10(-9), OPE increases with NO,; while if the concentration of NOx is higher than 14 x 10(-9), OPE decreases with NOx. The correlation analysis indicates that the concentrations of aromatics and OVOCs are positively correlated to OPE. Dry deposition of HNO3 and other NO, oxidation products may significantly impact the calculated OPE values, leading to overestimate. It is possible to correct such overestimate using the NOy/CO ratios obtained at an urban site and at Shangdianzi. However, this correction is less rigorous and the corrected OPE data remain to be validated. The uncorrected data can be viewed as the upper limit of the real OPE.