Influence of Tropical Weather and Northeasterly Air Mass on Carbonaceous Aerosol in the Southern Malay Peninsula

Carbonaceous aerosols play a key role in climate modification and exert a deleterious effect on human health. Thus, this study aimed to determine the thermally derived carbonaceous fraction in particulate matter (PM)_2.5 from the Southern Malay Peninsula, a tropical area in Malaysia, during January 2019 to March 2019. PM_2.5 was captured on quartz filters using a high-volume sampler on a 24 h basis. Eight of the carbon fractions were measured using the thermal optical reflectance method. Carbonaceous aerosol was thoroughly characterized by estimating elemental carbon (EC), organic carbon (OC), total carbon, secondary OC, soot-EC, and char-EC to determine the mechanism of emission from fossil fuel combustion, biomass, and secondary origins. The effect of local meteorological factors and air mass transport on the change in the light-absorbing aerosol fraction was also examined. Secondary organic sources and primary sources emitted 46 and 54% of OC, respectively. The estimated char-EC in this study was 10-fold higher than soot-EC, indicating that biomass burning and coal combustion were the predominant routes of EC emission, whereas petrol or diesel engines were the less predominant generators of soot-EC. Trajectory modeling showed that biomass fires in the Indochina region were the potential origin of carbonaceous aerosols transported from the northeasterly direction.