Chemical Compositions of Primary PM2.5 Derived from Biomass Burning Emissions

A number of field studies have provided evidence that biomass burning is one of the major global sources of atmospheric particles. In this study, we have collected PM 2.5 emitted from biomass burning combusted at open burning and laboratory chamber situations. The open burning experiment was conducted with the cooperation of 9 farmers in Chiba Prefecture, Japan, while the chamber experiment was designed to evaluate the characteristics of chemical components among 14 different plant species. The analyzed categories were PM 2.5 mass concentration, organic carbon (OC), elemental carbon (EC), ionic components (Na + , NH 4 + , Ca 2+ , Mg 2+ , K + , Cl − , NO 3 − and SO 4 2− ), water-soluble organic carbon (WSOC), water-insoluble inorganic carbon (WIOC), char-EC and soot-EC. OC was the dominant chemical component, accounting for the major fraction of primary PM 2.5 derived from biomass burning, followed by EC. Ionic components contributed a small portion of PM 2.5 , as well as that of K + . In some cases, K + is used as biomass burning tracer; however, the observations obtained in this study suggest that K + may not always be suitable as a tracer for biomass burning emissions. Also, the results of all the samples tested indicate relatively low values of char-EC compared to soot-EC. From our results, careful consideration should be given to the usage of K + and char-EC as indicators of biomass burning. The calculated ratios of WSOC/OC and WIOC/OC were 55.7% and 44.3% on average for all samples, which showed no large difference between them. The organic materials to OC ratio, which is often used for chemical mass closure model, was roughly estimated by two independent methods, resulting in a factor of 1.7 for biomass burning emissions.