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 SO₂, NO₂ and PM₁₀ 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 SO₂ (0.0514 ± 0.0390 mg/m³, n=1096), NO₂ (0.0416 ± 0.0135 mg/m³, n=1096) and PM₁₀ (0.1268 ± 0.0574 mg/m³, n=1095) were Pearson 6, Extreme Value and Log-Logistic distribution, respectively. According to the rollback equation, the emission source reduction of SO₂, NO₂ and PM₁₀ 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 PM₁₀ and NO₂ should be reduced to meet the AAQS while the SO₂ 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.