A Key Indicator of Transboundary Particulate Matter Pollution Derived from Indonesian Peatland Fires in Malaysia

We characterized ambient total suspended particulates (TSP) based on ground-based samplings in Malaysia during non-haze days and haze ones affected by Indonesian peatland fires. Furthermore, a key indicator of Indonesian peatland fire was determined based on chemical characterization of TSP in Malaysia. TSP samples were chemically analyzed to determine organic carbon (OC), elemental carbon (EC), inorganic ions, and biomarkers (solvent-extractable organic compounds derived from biomass burning). Regarding OC and EC, concentrations of OC1 and OP (pyrolyzed OC) defined by IMPROVE_A protocol increased remarkably during the haze episodes. On the contrary, there were no significant differences in concentrations of OC4, EC, and EC fractions between the haze and non-haze samples. Regarding inorganic ions, sulfate and ammonium concentrations increased in strong haze days, however, it is difficult to use these compounds as indicators for Indonesian peatland fires in light haze days due to the partial overlapping of the variation ranges of sulfate and ammonium concentrations in non-haze days. Concentrations of many biomarkers derived from cellulose, hemicellulose, and lignin pyrolysis products were significantly increased during strong haze days but not during light haze days except p-hydroxybenzoic acid. We proposed the OP to OC4 ratio as a potential indicator of transboundary haze pollution from Indonesian peatland fires at the receptor sites even in light haze.