| A continuous haze episode with high concentration of fine particulate matter occurred in Shanghai from May 19 th to May 21 th, 2010. Results of the online monitoring of ion composition in aerosols indicated that three secondary ions, sulfate, nitrate and ammonium, were the main contributors to this haze episode. Through pollution analysis, it could be found that favorable reaction conditions, sufficient gaseous precursors and atmospheric oxidation helped NO2 transform from gas to aerosol rapidly, and sulfate was transported back from sea surface after thorough secondary transformation of SO2 which was emitted from land. These two factors caused alternation of PM2.5 concentration peaks to form continuous haze pollution. Therefore, nitrogen oxides and sulfur dioxide should be controlled synergistically to effectively control haze pollution in Shanghai. For nitrogen oxides, local emission sources should be controlled strictly due to the fast transformation rate and complex effect. For sulfur dioxide, attention should be paid to regional joint control due to its long range transportion. |
