某区县冬春季PM2.5中碳质组分与二次生成特征初探OA

To clarify the seasonal variation patterns and secondary formation characteristics of carbonaceous components in fine particulate matter in a typical county-level area of southern Jiangsu,the concentrations of organic carbon(OC)and elemental carbon(EC)were measured using an OCEC-100 analyzer from October 2021 to March 2022,and the secondary organic carbon(SOC)contribution was estimated based on the minimum OC/EC ratio method.The results showed that the average concentrations of total carbon[ρ(TC)=ρ(OC)+ρ(EC)]in winter and spring were 6.95 μg/m3 and 6.59 μg/m3,respectively;although the absolute values were close,a higher proportion of TC in PM2.5 was observed in spring(20.38％),and it was reflected that the contribution of non-carbon components(e.g.,nitrate and dust)was greater in winter.High correlations between OC and EC were observed in both seasons(r=0.77 and 0.76),and the OC/EC ratios were found to be 3.68 and 2.83(both>2.00),from which it was indicated that significant SOC formation was present and stronger photochemical activity was also shown in winter.The SOC/OC ratio was as high as 42.18％in winter,but was sharply reduced to 12.17％in spring.Combined with the regional PMF source apportionment results in 2021,the high carbonaceous components in winter were mainly driven by primary sources such as coal combustion and biomass burning,together with active secondary transformation;while in spring,the SOC formation efficiency was reduced due to weakened primary emissions,boundary layer lifting,and relatively high humidity.The seasonal evolution characteristics of carbonaceous aerosols in this region and their associations with local pollution sources were revealed,and scientific evidence was provided for refined PM2.5 control.