| 24 hours PM2.5 aerosol samples were collected on the top floor of NO.4 classroom building,B area,Chengdu Campus,Sichuan agricultural University from July 2015 to April 2016.The water-soluble ions,the total sulfur?TS?content and the different types and concentrations of organosufates in PM2.5 aerosol samples,these determination results were carried out by means of using Ion Chromatography?IC?,Inductive Coupled Plasma-Atomic Emission Spectrometer?ICP-AES?and Liquid Chromatography/Electrospray Ionization/Triple Quadrupole Mass Spectrometry?LC-ESI-QQQ-MS?.And combined with the meteorological data and acidity simulation data,to discuss the total sulfur,inorganic sulfur?IS?,the formation cause and change characteristics of organosulfates.This study using IC for the analysis of 11 kinds of water-soluble ions?F-?Cl-?NO2-?SO42-?C2O42-?NO3-?Na+?NH4+?K+?Ca2+? Mg2+?in the samples.SO42-is one of the main forms of S in the atmosphere,which is regarded as the total amount of inorganic sulfur in this experiment.The results showed that sulfate average concentration in Chengdu campus,Sichuan Agricultural University is 8.47±2.82?g/m3,the summer average concentration is 17.04±4.09?g/m3,the average concentration of autumn value is 5.79±13.13?g/m3,the average concentration value in winter is 12.70±9.49p?g/m3.The year average concentration is 11.54±7.36?g/m3,we can see that the seasonal variation of the annual SO42-is summer>winter>spring>autumn.Conversion to the inorganic sulfur in the four seasons,inorganic sulfur concentrations,respectively in the spring of 2.83 ±0.94?g/m3,5.69±1.40?g/m3 in summer,1.93±1.04?g/m3 in autumn,4.24±3.17?g/m3 in winter,and the annual average is 3.85±2.46?g/m3.This study measured by ICP-AES for total sulfur in samples,the total sulfur concentration in spring is 3.31±0.87?g/m3,the average concentration in summer is 7.93±2.20?g/m3,the average concentration of autumn value is 2.88+1.57?g/m3,the average concentration value is 5.94±4.82?g/m3 in winter.The average concentration is 5.27±3.67?g/m3 of the year,annual trends:summer>winter>spring>autumn,which is similar to the seasonal changes of SO42-change rule.The difference between the total sulfur and inorganic sulfur is the organic sulfur in atmospheric aerosols.Result shows that the proportion of organic sulfur among total sulfur?OS/TS?in spring is 15.6±10.2%,27.1 ± 14.0%in summer,27.5±21.7%in autumn and 20.7± 14.2%in winter.The average percentage level is about 22%.In the average proportion of organic sulfur among total sulfur,the data of the summer and autumn is higher than the other two seasons.Furthermore,to analyze the specific species and concentration of organosulfate in each sample by LC-ESI-QQQ-MS.According to the different precursors,the organosulfate can be divided into three groups,isoprene-derived organosulfates,monoterpene-derived organosulfates and aromatic organosulfates.The results can be seen from the total seasonal measured organosulfates,namely 0.33ng/m3 in spring,,1.57ng/m3 in summer,0.52ng/m3 in autumn and 0.34ng/m3 in winter,the average is 0.64ng/m3,annual change level:summer>autumn>winter? spring.And the emission of m/z 215 is more than 50%of the annual emissions.The content of monoterpene-derived organosulfates take up above 95%for the experiment,20.10ng/m3 in spring,34.53ng/m3 in summer,22.05ng/m3 in autumn and 34.09ng/m3 in winter,the average is 29.13ng/m3.From the overall variation of seasons,summer ?winter>spring ? autumn change.The seasonal variation of this kind of organosulfate appears double-peak.More than one source,not only the plant source,there may be a source of biomass,including m/z 265 seasonal emissions are much higher than other types of organosulfates,presumably from anthropogenic sources.Aromatic organosulfates mainly from anthropogenic sources,including fuel such as coal combustion and vehicle exhaust,from the total measured,the average values in spring,summer,and autumn are close to 0.06ng/m3 and 0.17ng/m3 in winter,the average is 0.10ng/m3.The average pH value of the year is 3.15.The average pH value of spring is 4.21,4.02 in summer,3.70 in autumn and 2.90 in winter,the pH levels of the four seasons is springc ? summer>autumn>winter.Therefore,the acidity level is winter>autumn>summer ? spring.The isoprene organosulfate m/z 215 showed higher concentrations in summer samples than in those of the other seasons.Simultaneouly,m/z 169 showed higher concentrations in high acidic aerosols and under highly humic climate.Additionally,both monoterpene and benezic organosulfates showed high concentrations in high acidic aerosols and highly polluted conditions. |
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