| Recent years, organosulfates(OSs) have been found as a significant component of secondary organic aerosols from both smog chamber experiments and field measurements. Some research shows that the concentration of organic acid esters in the air particulate matter is relatively high in the atmosphere where the sulfur dioxide is greater. The sulfur dioxide pollution has been serious for a long time in China. Therefore, it is a great significant event to evaluate the contribution of OSs to the atmospheric particles.In this study, an indirect method was developed to estimate OSs in aerosol particles based on their sulfate functional group. The carbon content in OSs was estimated based on the relationship between organic carbon and organic sulfur in OSs obtained from chamber aerosols. In our study, sodium dodecyl sulfate was selected as the standard to determine and optimize the dissociation conditions of OSs in atmospheric particles. The mass concentrations of sulfate ion before and after dissociation are measured by ion chromatography as those of inorganic sulfate(IS) and total sulfate(TS), respectively. The mass concentrations of organic sulfate, which is the sulfate in OSs, are estimated as a difference between TS and IS. The mixtures of sodium sulfate and SDS with various molar ratios of IS and OS were prepared to mimic the coexistence of inorganic sulfate and OSs in ambient aerosol particles. A series of experiments were conducted using the standard mixtures to evaluate the feasibility of the developed method for the quantification of organic and inorganic sulfate in the atmospheric particles. What's more, the error analysis of the sulfate content in the OSs was carried out, and the result shows that the error range of this method to determine sulfate content in OSs is 5.74%?37.71%.The secondary organic aerosols generated from the ozonolysis of three biogenic precursors(?-pinene, ?-pinene and isoprene) were taken as the study object. The relationship between organic sulfur and organic carbon in OSs was obtained through the variations of organic sulfur content and organic carbon content in SOA generated from three biogenic precursors under the condition of inorganic seed aerosols with different sulfur content and same acidity. The linear fitting result of experimental data shows that the ratio of organic carbon to organic sulfur in OSs is 10:1. It is also found that the influence of inorganic seed aerosol acidity on the OSs formation was greater than sulfur content of inorganic seed aerosol.In this study, the pollution characteristics of OSs in PM2.5 samples at four sites in Shenzhen were studied. The four sites vary in pollution sources. The mass concentration of OSs in ambient air is 2.71 ?g C/m~3 in winter, accounting for 29.42% of TOC. The mass concentration of OSs in ambient air is 1.18 ?g C/m~3 in summer, accounting for 13.76% of TOC. The mass concentrations of OSs in four different sampling sites were in order of power plant(PP) >Longhua > Xili >HITSZ. The contributions of OSs to TOC were in order of Longhua >PP > Xili >HITSZ. The contributions of OSs to PM2.5 total mass were Longhua >PP > Xili >HITSZ. In addition, the correlation analysis of the PM2.5 components shows that the organic sulfate was significantly positively correlated with the inorganic sulfate on the ambient particles, and this relationship of inorganic sulfate and organic sulfate indicates that OSs may be formed by a series of atmospheric chemical reactions. |
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