Articles | Volume 18, issue 4
Atmos. Chem. Phys., 18, 2585–2600, 2018
Atmos. Chem. Phys., 18, 2585–2600, 2018

Research article 21 Feb 2018

Research article | 21 Feb 2018

Chemical characterization of fine particulate matter emitted by peat fires in Central Kalimantan, Indonesia, during the 2015 El Niño

Thilina Jayarathne1, Chelsea E. Stockwell2, Ashley A. Gilbert1, Kaitlyn Daugherty1, Mark A. Cochrane3, Kevin C. Ryan4, Erianto I. Putra3,5, Bambang H. Saharjo5, Ati D. Nurhayati5, Israr Albar5,a, Robert J. Yokelson2, and Elizabeth A. Stone1,6 Thilina Jayarathne et al.
  • 1University of Iowa, Department of Chemistry, Iowa City, IA 52242, USA
  • 2University of Montana, Department of Chemistry, Missoula, MT 59812, USA
  • 3Appalachian Laboratory, University of Maryland Center for Environmental Science, Frostburg, MD 21532, USA
  • 4FireTree Wildland Fire Sciences, L.L.C., Missoula, MT 59801, USA
  • 5Bogor Agricultural University, Faculty of Forestry, Bogor 16680, Indonesia
  • 6University of Iowa, Chemical and Biochemical Engineering, Iowa City, IA 52242, USA
  • anow at: Directorate General of Climate Change, Ministry of Environment and Forestry, Jakarta 10270, Indonesia

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.

Short summary
Fine particulate matter (PM2.5) emissions from Indonesian peat burning were measured in situ. Fuel-based emission factors from 6.0–29.6 gPM kg-1. Detailed chemical analysis revealed high levels of organic carbon that was primarily water insoluble, little to no detectable elemental carbon, and alkane contributions to organic carbon in the range of 6 %. These data were used to estimate that 3.2–11 Tg of PM2.5 were emitted by the 2015 peat burning episodes in Indonesia.
Final-revised paper