Identification and validation of marker compounds for fine particle emitted from sub-type biomass burning

Marker components are critical for accurately identifying fine particle (PM 2.5 ) sources. Current marker identification is subjective, and the widely adopted markers to distinguish sub-types of biomass burning (BB) emissions are impossible. Here, PM 2.5 samples from the combustion of ten biomass types were collected, and 102 chemical components were analyzed. Results indicated that the mass fractions of K⁺, K, and levoglucosan (LEV) varied in 0.1%–8.4% (2.4 ± 2.2%), 0.1%–14.1% (3.2 ± 3.1%), and 0.1%–4.9% (2.1 ± 1.4%). Source profiles for the ten sub-types of BB differed notably according to their coefficient of divergence values (0.33–0.72). It implied that there existed species which can separate PM 2.5 from the ten types of BB. Ten widely used specific species ratios in literatures cannot effectively distinguish sub-types of BB due to the value overlap. A k-means identified LEV and fatty acid (C16:0) as the common markers for the ten sub-types of BB. C16:0 was firstly proposed and verified as a marker for BB here. With a random forest and the current dataset, the subtype-specific markers for only four sub-type sources were identified and verified. We indicated that there is no necessary relationship between markers and their mass percentages. This study provides a basic database and scientific reference for sub-type source apportionment and species-based emission inventory developing.