Intercomparison of two different thermal-optical elemental carbons and optical black carbon during ABC-EAREX2005

A formal intercomparison of fine particle elemental (black) carbon is conducted involving three real-time semi-continuous measurement systems. Two-hourly interval time-resolved measurements of organic carbon (OC) and elemental carbon (EC) were performed at the Gosan site, Korea during Atmospheric Brown Clouds–East Asian Regional Experiment 2005 (ABC-EAREX2005) campaign. They were operated by the same semi-continuous field carbon instruments of Sunset Laboratory (thermal optical transmittance) in PM2.5 particulate. However, their thermal protocols (four and two steps for OC and five and two steps for EC) were different. The co-located 1 min black carbon (BC) concentrations were compared by an Aethalometer for an intercomparison study. As a result, the poor R2 of OC between two different temperature protocols suggested that OC can be significantly more biased by the slight differences of maximum temperature (870 and 840 °C) and a number of temperature steps (four steps and two steps) with their hold times. However, EC that is a smaller fraction of total carbon (TC) shows the good agreement between two different protocols, which are under a mixture of 2% O2 and 98% He in six temperature steps and two temperature steps as max as 900 and 880 °C with the slope of 1.05±0.15 (R2 of 0.98). The different slopes between EC and BC, which show the range of 1.23–1.61, demonstrate the variability of the attenuation coefficient of the BC particulate.