Source indicators of biomass burning associated with inorganic salts and carboxylates in dry season ambient aerosol in Chiang Mai Basin, Thailand

► PM10 pollution in Chiang Mai, Thailand, during biomass burning. ► Two sites and two types of pollution (episodic and non-episodic) compared. ► Carboxylates show traffic, photochemical and biomass sources in PM10 episodes. ► Levoglucosan highs indicate biomass burning major cause of PM10 episodic pollution. ► Levo/Manno ratio shows hardwood burning, particularly, leads to PM10 episodes.