Source apportionment of atmospheric pollutants based on the online data by using PMF and ME2 models at a megacity, China

•Source apportionment of atmospheric pollutants was conducted by using the online datasets.•Source contributions and profiles obtained from PMF and ME2 models were consistent.•Secondary sources, vehicle exhaust, coal combustion were major sources during summer.

From 1st June to 31st August 2015, the online datasets (the water soluble inorganic ions (WSIIs), OC and EC in PM2.5, and SO2, NO2, NO) were measured continuously at Tianjin. Source apportionment of atmospheric pollutants was carried out by using PMF and ME2 models based on the online datasets. During summer in Tianjin, the ammonium sulfate/ammonium hydrogen sulfate might be major forms of sulfate in the atmospheric aerosol, while the ammonium nitrate might be major forms of nitrate. The poor correlation between OC and EC might be caused by the changes of emission sources and the production of secondary organic carbon (SOC). Five source-categories that contributed to atmospheric pollutants were extracted by PMF and ME2 models, respectively. The profiles calculated by PMF and ME2 models were consistent, and the source contributions estimated by the two models were also similar. The correlations (R2 = 0.84-0.94) were better on the time series of the contributed concentrations for the same source-category calculated from PMF and ME2 models. The source-categories were identified as secondary sources (the contribution of 25.4-26.1%), vehicle exhaust (23.3-25.4%), coal combustion (16.5-18.2%), crustal dust (13.2-14.0%) and biomass burning (9.1-10.2%). For the same source-category identified from PMF and ME2 models, the differences of profiles might be attributed to the differences of calculated methods from the two models and the uncertainties of the online datasets.

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