AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Dynamics of Light Absorption by Biomass Burning Organic Aerosol Photochemically Aged Using the Ambient Sunlight
MIN ZHONG, Myoseon Jang, University of Florida
Abstract Number: 283 Working Group: Combustion
Abstract The light absorption of wood burning organic aerosol (WBOA) was measured as a function of photooxdiation time in a 104 m3 outdoor chamber with ambient sunlight. The experiments were conducted under different humidity and NOx conditions. The results showed that the light absorption of WBOA was dynamically changing during the aging process. The light absorption of WBOA increased in the morning and then decreased in the afternoon due to the competition among gas-particle partitioning, particle phase reaction, SOA formation and sunlight bleaching. More than 90% concentration reduction in PAH and levoglucosan indicated the progress of partitioning and particle phase reaction. WBOA enhanced up to 1.5 times caused by SOA formation. The light absorption of organic aerosol was found to be insensitive to NOx and RH, except high RH up to 85%. Under the high RH condition, the light absorption of WBOA kept decreasing. Such trend might be due to the more active particle phase reaction with higher water content. At RH of 85%, the water content of fresh particle was 40%, aged particles about 20%. The outdoor measurement was also compared with the ambient data obtained in a fire event. In the ambient, the light absorption of biomass burning organic aerosol continuously reduced from morning to afternoon. No color enhancement was observed. The difference between chamber observation and ambient data needs further investigation.