Multiple organic tracer analyses of biomass changes affected by the open burning of rice residues

Abstract

Daily PM2.5 samples were collected at a rural site in Fukui City, Japan, over two months from September to November 2019, covering the rice harvest and postharvest periods, to understand the changes in levels of combustion of various types of biomass during the autumn season. Four organic tracer components of biomass combustion—levoglucosan, mannosan, vanillic acid, and dehydroabietic acid—were analyzed from the PM2.5 samples to reveal their relationships with different types of biomass, such as plants and forests. The ratio of levoglucosan-to-mannosan, a typical organic tracer component of biomass combustion, changed from an average value of 36 ± 17 during the rice harvest season to a value of 13 ± 4 after the rice harvest season, indicating a shift in the primary combustibles from crop residues such as rice straw to other combustibles. The concentration and proportion of mannosan and dehydroabietic acid increased after the rice harvest season, indicating an increase in the proportion of conifers among biomass-burning species. Our new analysis of multiple organic biomass burning (BB) traces indicated the availability of the elucidation of compositional changes in different BB types.