Particle size characteristics of levoglucosan in ambient aerosols from rice straw burning

Agricultural residue burning in Asia is an important source of atmospheric aerosol particles. This study investigates the impact of post-harvest burning of rice fields on the air quality in Taiwan, a subtropical island in East Asia. Size-resolved measurements of the anhydrosugar levoglucosan (biomass burning tracer derived from the thermal breakdown of cellulose) were conducted before, during and after an episode of intensive rice straw burning at a rural and suburban site. While substantially enhanced levoglucosan concentrations were observed during the active rice straw burning episode (up to 1400 ng m−3), fairly high values of the smoke tracer were measured throughout the entire study period. Moreover, unusually high levoglucosan levels were present in aerosol particles with aerodynamic diameters larger than 10 μm (PM>10), possibly influenced by the ambient atmospheric conditions, such as high relative humidity, in addition to unique properties of rice straw smoke and the specific burning practices of rice fields.