Emissions and characteristics of particulate matter from rainforest burning in the Southeast Asia

The burning of tropical rainforests in the Southeast Asia emits considerable particulate matter (PM), which has significant effects on air quality and human health. Lacking of reliable local EF_PM for rainforest burning in the Southeast Asia is one of the most important causes for uncertainty of the estimated pollutant emissions. In this study, 23 types of rainforest plants, including herbaceous, shrubs, evergreen trees and deciduous trees were burned to determine emission factors of PM and multiple chemical species, including organic carbon (OC), elemental carbon (EC), water soluble ions (WSIs), and elements using a custom-made dilution system. EF_PM for the four vegetation types was relatively higher for burning of deciduous trees, followed by evergreen trees, shrubs and herbaceous. EF_PM in the Southeast Asia was higher than those in the North America, South America and Africa, with biomass type and ambient temperature and humidity as the determinant factors. Organic matter was the dominant constituent of PM, accounting for 57%, followed by EC, WSIs and elements. Source profile of WSIs varied larger than those of OC, EC and elements for different biomass type and areas. For example, the fraction of K⁺, a typical biomass burning tracer, to WSIs was 30% and 28% in the Southeast Asia and North America, respectively, which was almost 2 times lower than those in the Europe. Finally, the temporal and spatial scales of PM, OC, and EC emissions from rainforest burning in the Southeast Asia in 2016 were estimated, based on the updated measured EFs. The annual emissions (minimum-maximum) were 1527–2834 Gg, 529.9–1100 Gg, and 81.02–150.4 Gg for PM, OC and EC, respectively. Our results suggest that using of EF_PM reported in other regions would lead to an underestimation of PM emissions in the Southeast Asia.