Abstract

Understanding of the characteristics of water-soluble inorganic ions (WSI) in fine particulate matter (PM2.5) emitted during forest fires has paramount importance due to their potential effect on ecosystem acidification. Thus, we investigated the emission factors (EFs) of ten most common WSI from combustion of leaves and branches of ten dominant tree species in Chinese boreal and sub-tropical forests under smoldering and flaming combustion stages using a self-designed combustion unit. The results showed that EF of PM2.5 was three times higher for the boreal (6.83 +/- 0.67 g/kg) than the subtropical forest (1.97 +/- 0.34 g/kg), and coniferous species emitted 1.5 times more PM2.5 (5.35 +/- 0.64 g/kg) than broadleaved species (3.45 +/- 0.37 g/kg). EF of total WSI was 1.27 +/- 0.08 g/kg for the boreal and 1.08 +/- 0.07 g/kg for the subtropical forest and 1.28 +/- 0.09 and 1.07 +/- 0.06 g/kg for broadleaved and coniferous species, respectively. Individual ionic species also varied significantly between forest types and species within forest types, and K+ and Cl- were the dominant ionic species in PM2.5, accounting for 25% and 30% for the boreal forest and 23% and 27% for the subtropical forest, respectively. Emissions of NO2- and SO42- were the lowest, accounting for 3% and 5% for the boreal forest and 4% for each of the subtropical forests, respectively. Combustion of leaves emitted significantly more ionic species (1.29 +/- 0.05g/kg) than branches (1.05 +/- 0.07 g/kg), and smoldering consistently emitted more ionic species (1.49 +/- 0.09 g/kg) than flaming combustion (0.88 +/- 0.03 g/kg). The cation to anion ratio was >= 1.0, suggesting that the particulate matter is neutral to alkalescent. As a whole, our findings demonstrate that forest fire in these regions may not contribute to ecosystem acidification despite the emission of a considerable amount of WSI during forest fires.

Keywords

acid rain; aerosol; biomass burning; forest fire; PM2.5

Published in

Forests
2019, Volume: 10, number: 11
Publisher: MDPI

SLU Authors

• Tigabu, Mulualem

  • Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences
    
  • Fujian Agriculture and Forestry University

UKÄ Subject classification

Ecology
Forest Science


Publication identifier

DOI: https://doi.org/10.3390/f10110994

Permanent link to this page (URI)

https://res.slu.se/id/publ/103375