Abstract
Abstract. Fine particulate matter (PM2.5) was collected in situ from peat smoke during the 2015 El Niño peat fire episode in Central Kalimantan, Indonesia. Twenty-one PM samples were collected from 18 peat fire plumes that were primarily smoldering with modified combustion efficiency (MCE) values of 0.725–0.833. PM emissions were determined and chemically characterized for elemental carbon (EC), organic carbon (OC), water-soluble OC, water-soluble ions, metals, and organic species. Fuel-based PM2.5 mass emission factors (EFs) ranged from 6.0 to 29.6 g kg−1 with an average of 17.3 ± 6.0 g kg−1. EC was detected only in 15 plumes and comprised ∼ 1 % of PM mass. Together, OC (72 %), EC (1 %), water-soluble ions (1 %), and metal oxides (0.1 %) comprised 74 ± 11 % of gravimetrically measured PM mass. Assuming that the remaining mass is due to elements that form organic matter (OM; i.e., elements O, H, N) an OM-to-OC conversion factor of 1.26 was estimated by linear regression. Overall, chemical speciation revealed the following characteristics of peat-burning emissions: high OC mass fractions (72 %), primarily water-insoluble OC (84 ± 11 %C), low EC mass fractions (1 %), vanillic to syringic acid ratios of 1.9, and relatively high n-alkane contributions to OC (6.2 %C) with a carbon preference index of 1.2–1.6. Comparison to laboratory studies of peat combustion revealed similarities in the relative composition of PM but greater differences in the absolute EF values. The EFs developed herein, combined with estimates of the mass of peat burned, are used to estimate that 3.2–11 Tg of PM2.5 was emitted to atmosphere during the 2015 El Niño peatland fire event in Indonesia. Combined with gas-phase measurements of CO2, CO, CH4, and volatile organic carbon from Stockwell et al. (2016), it is determined that OC and EC accounted for 2.1 and 0.04 % of total carbon emissions, respectively. These in situ EFs can be used to improve the accuracy of the representation of Indonesian peat burning in emission inventories and receptor-based models.
Highlights
In recent decades, peatland fires in Southeast Asia, especially the Indonesian provinces of Sumatra, Kalimantan, and Papua as well as Malaysian Borneo, have become more frequent in occurrence (Page et al, 2009; Langner and Siegert, 2009; Van der Werf et al, 2010)
This paper focuses on the particulate-phase chemistry, and a comprehensive description of gas-phase emissions and optical properties (brown carbon (BrC), black carbon (BC), and the mass absorption coefficients for the bulk organic carbon (OC) due to BrC) is given in Stockwell et al (2016)
The percent difference across samples collected sequentially from the same plume was 57, 37, and 8 % for plumes E, F, and W, respectively, indicating some temporal variability in emissions within the fire as it progresses. This in-plume variability in the field could result from the spread and progression of the fire, consistent with peat samples burned batch-wise in laboratory settings that show EFPM2.5 decreases on the timescale of hours during combustion (Black et al, 2016)
Summary
Peatland fires in Southeast Asia, especially the Indonesian provinces of Sumatra, Kalimantan, and Papua as well as Malaysian Borneo, have become more frequent in occurrence (Page et al, 2009; Langner and Siegert, 2009; Van der Werf et al, 2010). The 2015 fires burned ∼ 1 million ha of tropical forests and peatlands in Indonesia, releasing ∼ 0.2 Pg C of carbon to the atmosphere (Huijnen et al, 2016) These values are well below the 1997–1998 estimates of ∼ 2 million ha of burned peatland area that released ∼ 1.7 Pg C of carbon to the atmosphere in 2015 (Page et al, 2002; Chisholm et al, 2016; Huijnen et al, 2016; Tacconi, 2003). It was estimated that more than 40 million people suffered from continuous exposure to peat smoke during this episode and significant increase of premature deaths were reported due to respiratory and cardiovascular diseases (Koplitz et al, 2016). Socioeconomic, and health impacts, the peatland fire emissions are still under-studied with respect to their chemical and physical properties
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
