An Improved Thermal Oxidation Method for the Quantification of Organic and Black Carbon in Soot Based on the Difference of Pyrolytic Behavior

摘要

Pyrolysis combustion methods (also called as thermal oxidation methods) are widely used for the quantification of organic carbon (OC) and black carbon (BC) in aerosols. However, a part of OC aerosols undergoes charring to form pyrolytically generated elemental carbon (PEC) during OC evaporated in the inert atmosphere, and PEC seriously affects the accuracy of thermal oxidation method. In this study, the pyrolytic behaviors of OC, PEC and BC particles in both inert and air atmosphere have been studied in detail in order to develop a new correction method of PEC for the thermal oxidation method. Our results indicate that weight-loss rate of PEC is 5.6 times faster than that of BC particles at 500 °C in air atmosphere, although they begin to lose weight at approximately the same temperature. Based on the difference of the weight-loss rate between PEC and BC, a new method of PEC correction was advanced for the thermal oxidation method. With the help of the new PEC correction method and thermal analyzer, we successfully determined OC and BC concentrations in actual soot sample, atmospheric aerosol samples and artificial soot samples. The results obtained with our PEC correction method are consistent well with the real value or those analyzed with thermal-optical method, suggesting that the novel PEC correction method have a high accuracy.