| Aerosols have great effects on regional and global climate change, and human health through changing atmospheric radiation, atmospheric chemistry, and cloud and precipitation formation leading to the Earth's energy budget imbalance or global climate change. Providing site for pollution accumulation, aerosols advance gas-to-particle conversion in the atmosphere and make air pollution more complicated. Different sources and cross-contamination makes it more difficulty to investigate aerosol physical and chemical properties, and formation mechanism.An online analyzer of Monitoring for AeRosols and Gases (MARGA) was employed to measure major water-soluble inorganic ions in PM2.5 at 1-h time resolution in Shanghai for one year. The chemical compositions, temporal variations, and diurnal variations of aerosols were studied in detail. Combined with the impacts of meteorological conditions, this work is to investigate the evolution and conversion of aerosols in the period of haze pollution based on a high time resolution dataset of aerosol water soluble ions. Furthermore, it was also investigated that especial events, i.e. biomass burning and dust, have great effects on the air quality.The major results were summarized as follows:1,The total water-soluble ions of aerosols in spring and winter were more than that in summer and autumn. SO42-, NO3-, and NH4+ were the dominant water-soluble fractions in PM2.5, accounting for 87.78%,87.90%,84.13%, and 76.89% of the total water-soluble ion concentration in spring, summer, autumn and winter, respectively. In addition, these ions had similar diurnal variations, indicating that they behaved the same formation mechanism. Under high atmospheric oxidation ability and steady atmosphere condition, the secondary pollution resulted from a significant increase of sulfate and nitrate aerosols which were oxidized from large amounts of anthropogenic pollution gases of SO2 and NO2 in the urban atmosphere.2,It was found that gas-to-particle conversion in the atmosphere could result in the formation of haze pollution. Despite local pollution, Shanghai also acts as a receptor of huge anthropogenic emissions by remote transportation under the influence of the monsoon system. Therefore, coexistence of dust, industrial and biomass burning pollutants in Shanghai complicated the formation mechanism of haze pollution. In summer, haze pollution event occurred because of biomass burning emission. K+, in the form of KCl, was an excellent indicator to be used in estimating biomass burning emission and tracing carbonaceous aerosol long-range transport in the atmosphere. Precursor gases of SO2 and NO2 were converted into SO42- and NO3- on the surface of pre-existing KCl particles, and the complicated pollution was responsible for a combining contribution of biomass burning aerosols directly from biomass burning emission and known secondary aerosols linked to local emission.3,Shanghai may also be influenced by dust transmission from north in spring, leading to the occurrence of haze pollution. The alkaline particles due to dust transmission offered the site for acid gas adsorption, i.e. SO2 and NOX, promoting SO2 to SO42- and NOx to NO3- conversions. These gas-to-particle conversions will arouse the complicated pollution in Shanghai. |
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