Characteristics Of Carbonaceous Components And Stable Isotope Tracing In PM_1.1 And Biomass In Nanjing

The concentrations of-OC and EC in PM1.1 collected from Nanshi and Nanhua in 2011 were analyzed using DRI Model 2001A Thermal Optical Carbon Analyzer.In addition,source apportionment was simultaneously evaluated.The results show that the annual average concentrations of OC and EC in PM1.1 were 10.10μg·m-3 and 2.52μg·m-3 in NS area,and 11.22μg·m-3 and 3.12μg·m-3 in NH area,respectively.This indicates that OC and EC pollution in NH was more serious than that in NS area.Meanwhile,the concentrations of OC and EC in winter and spring were obviously higher compared to those in summer in these two sampling sites,which is mainly ascribed to the increased coal combustion and the unfavorable emission condition of air pollutants in summer and spring.We note that SOC/TOC value was the highest in summer and the lowest in winter.In addition,SOC concentration was observed to present a positive correlation with ozone concentrations,which indicates that the photochemical reaction was a main way for SOC formation in autumn.Stable isotopic compositions(δ13C)of elemental carbon(EC)in PM1.1 in north suburb of Nanjing region were determined in order to quantitatively evaluate the carbon sources of atmospheric fine particles during different seasons.Besides,δ13C values from potential sources such as coal combustion,vehicle exhaust,biomass burning and dust were synchronously measured.The results showed that the average 813C values of EC in PM1.1 in winter and summer were-23.89±1.6‰ and-24.76±0.9‰,respectively.By contrast to δ13C values from potential sources,we concluded that the main sources of EC in PMi.i were from the emission of coal combustion and vehicle exhaust.The higher δ13C values in winter than those in summer were chiefly attributed to the more coal consumption.δ13C values of EC in PMi.i presented a seasonal change,indicating that the contribution of these two sources to PM1.1 in winter and summer varied significantly.The contribution of coal origin to EC in PM1.1 might increase to 73.9%in winter.Combining with the concentrations of SO42-and K+ in PM1.1,the high δ13C values of EC on 24 December and 27 December 2013 were ascribed to the extra input of corn straw burning in addition to coal combustion and vehicle exhaust.Emission factor of OC and EC in biomass combustion reaches the maximum within 0.43-0.65μm and<0.43μm no matter in the bright burning or smoldering conditions and the isotope fractionation effect in presence of two combustion conditions.