[Seasonal Variation and Source Analysis of Water-soluble Inorganic Salts in PM in the Southern Suburbs of Beijing].

In order to study the variation of water-soluble inorganic ions in the four suburbs of Beijing using the atmospheric fine particulate matter rapid trapping system and chemical composition analysis system (RCFP-IC), we carried out measurements for nine water-soluble inorganic ions (Cl, NO, NO, SO, Na, NH, K, Mg, Ca) in PM with continuous on-line observations for one year in Beijing's southern suburbs in 2016. The transport process of pollutants and the potential sources of pollutants were evaluated by combining a trajectory clustering method and potential source contribution factor analysis method (PSCF). During the observation period, the total concentration of the nine water-soluble inorganic ions was 38.6 μg ·m, and results showed that the concentration in winter and spring was high and in summer and autumn was low. The order of the concentration from high to low was SO > NO > NH > Ca > NO > Cl > Na > K > Mg. In winter, the SO, NO and NH accounted for 75.7% of the total measured water-soluble ions, followed by 72.8% in spring and 60.2% in summer. With an increase in air pollution, the concentrations of SO, NO, and NH increased significantly, indicating that SO, NO, and NH were closely related to the deterioration of air quality. SO was dominant in the formation of secondary ions compared to NO and NH; and SO, NO, and NH had significant diurnal variations. The diurnal variation of the SO statistic (hours) was bimodal, and the peak values were at about 10:00 and 18:00. The diurnal variation of NO and NH had single peaks, with the peak appearing at 10:00. The trend of the diurnal variation for these two ions was similar. Finally, the sources of pollution in the southern suburbs of Beijing mainly included secondary sources, coal-fired sources, and mixed sources of dust and dust. The main potential source of pollution in the southern suburbs was in the southeastern part of the observation site, while the northeastern airflow was favorable for the diffusion and dilution of pollutants.