Exploring the Influence of 34S Fractionation From Emission Sources and SO2 Atmospheric Oxidation on Sulfate Source Apportionment Based on Hourly Resolution δ34S‐SO2/SO42−

Abstract

AbstractSulfate (SO42−) sources are unclear leading to the underestimation of its concentration in the model. Hourly resolution δ34S‐SO2 and δ34S‐SO42− values of three haze episodes (EP1‐EP3) were synchronously collected for the first time to quantify the influence of 34S fractionation from emission sources (e.g., coal combustion) and SO2 atmospheric oxidation on SO2/SO42− source apportionment. After considering the 34S fractionation from coal combustion and atmospheric oxidation, the reasonable and logical source contributions of SO42− were obtained, showing highly consistent with that of Positive Matrix Factorization model results. Considering the 34S fraction from atmospheric oxidation, the source apportionment of SO2/SO42− obtained by hourly resolution δ34S‐SO2 and δ34S‐SO42− can more accurately reflect the dynamic changes of emission sources. Traffic emissions (49%) and coal combustion (46%–65%) were the major contributors to SO2/SO42− in EP1 and EP2‐EP3, respectively. However, obvious deviations of coal combustion contribution were found without considering 34S fractionation from coal combustion. Especially for the northwest transmission channels in EP2‐EP3, the deviation values accounted for 17.1%–38.5% of secondary SO42−. Moreover, δ34S was considered as a more sensitive source indicator than SO2 concentration by the results comparison of 34S technique and air quality model (Nested Air Quality Prediction Model System), which can provide more reliable evidence for SO2 emission control.