The statistical distributions of SO2, NO2 and PM10 concentrations in Xi'an, China

The paper analyzed the three-year (from 2006 to 2008) concentration data of SO 2 , NO 2 and PM 10 with routine monitoring in Xi'an, and selected several common statistical distribution models to fit the observational data. The results showed that the most appropriate distribution models representing the daily average concentration of SO 2 (0.0514 ± 0.0390 mg/m 3 , n=1096), NO 2 (0.0416 ± 0.0135 mg/m 3 , n=1096) and PM 10 (0.1268 ± 0.0574 mg/m 3 , n=1095) were Pearson 6, Extreme Value and Log-Logistic distribution, respectively. According to the rollback equation, the emission source reduction of SO 2 , NO 2 and PM 10 to meet the secondary standards of ambient air quality standard (AAQS) is also estimated, i.e. -16.7%, 3.8% and 21.1%, respectively. Therefore, in order to improve the air quality in Xi'an, the average concentration of PM 10 and NO 2 should be reduced to meet the AAQS while the SO 2 concentration meet to the AAQS with the environmental capacity of 16.7% in future. It can offer some referenced suggestions to develop effective air pollution control strategies for environmental protection departments.