Emission factors of PM<inf>2.5</inf>-Bounded selected metals, organic carbon, elemental carbon, and water-soluble ionic species emitted from combustions of biomass materials for source Apportionment—A new database for 17 plant species

Abstract

Over the past few years, burning agricultural or crop residues has resulted in serious air pollution, particularly in northern Thailand. In this study, constant endeavours were made to achieve the first-hand emission factors (EFs) of water-soluble ionic species (WSIS), organic carbon, elemental carbon, and selected metals emitted from the combustion of 17 plant species. The average EF values of organic carbon (OC) and elemental carbon (EC) ranged from 280 g kg−1 to 1441 g kg−1 and from 32 g kg−1 to 142 g kg−1, respectively. Sugarcane burning shows the highest EFs of toxic metals, such as V, Cr, Co, Ni, and Pb, which is concerning because Thailand is the world's second largest sugar exporter. The comparatively high percentage contribution of Cl− coupled with extremely low levels of K+ resulted in questions on its reliability as a chemical tracer for maritime aerosols and biomass burning particles, respectively. OC/EC ratios varied from 4.68 (Leucaena leucocephala) to 11.4 (Terminalia catappa) with the average value of 8.88 ± 1.72. Further attempts to investigate the most suitable diagnostic binary ratios of metals representing biomass burning were conducted using 2D plots of Zn/Mn, Fe/Zn, Fe/Cu, Ni/Co, Mn/Cr, Ni/V, Al/Si, and Pb/As. In this study, Mn/Cr versus Ni/V and Pb/As versus Al/Si can be used as diagnostic binary ratios to classify biomass-burning-related aerosols.