Abstract
For particulate carbon analysis, by the widely used thermal method, the pyrolysis of organic carbon (OC) causes an overestimate of elemental carbon (EC). However, recently the thermal/optical method, that is capable of pyrolysis correction by monitoring the reflected and/or transmitted lights of a sample filter during analysis, is becoming popular. In this study, the thermal and the thermal/optical methods were compared using the same ambient samples collected at an urban and a rural site in winter and summer. For both methods, OC and EC were separated at 550° in 100% a helium atmosphere. There was less difference for the total carbon (TC) concentration, whereas EC and OC concentrations were varied with the methods. For EC, the concentration by the thermal/optical method was smaller than the thermal method (the slope of regression line was 0.70 for the thermal vs. the thermal reflectance method; 0.34 for the thermal vs. the thei: nal transmittance method). Moreover, the influence of seasons, sampling sites, and particle size on EC and OC concentrations were also examined; however, these factors did not contribute as much as the analysis methods. Additionally, using samples with a 100% cutoff diameter of 10μm collected by a low volume sampler (LVS) and a high-volume sampler (HVS) simultaneously, the total mass and carbonaceous particle concentrations measured from LVS and HVS samples were compared. The total mass, EC, and OC concentrations by HVS were about 15%, 20%, and 40% smaller than LVS, respectively.
