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Aerosol Emissions from Long-lasting Smoldering of Boreal Peatlands: Chemical Composition, Markers, and Microstructure

Category: Aerosol and Atmospheric Chemistry

Volume: 19 | Issue: 3 | Pages: 484-503
DOI: 10.4209/aaqr.2018.08.0302
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Olga B. Popovicheva 1, Guenter Engling 2, I-Ting Ku3,4, Mikhail A. Timofeev1, Natalia K. Shonija1

  • 1 Institute of Nuclear Physics, Moscow State University, 119991 Moscow, Russia
  • 2 Division of Atmospheric Sciences, Desert Research Institute, Reno, NV 89512, USA
  • 3 Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan
  • 4 Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, USA

Highlights

Comprehensive characterization of aerosols from long-lasting peat smoldering burns.
High OC/EC ratio, AAE, and tarr ball as chemical, optical markers and micromarkers.
Peat bog fires in boreal region produce large amounts of smoke, affecting a megacity.


Abstract

As large-scale peat burning emissions can severely impact the environment and human health, it is crucial to assess the characteristics of smoke aerosol at the source and at down-wind locations. From March until late summer in 2014, the Tver region, north of the city of Moscow, was considerably affected by long-lasting peat bog fires. Peat bog smoldering emissions from three types of smoke (underground, inside grass, and above grass) were analyzed by an extensive suite of instrumentation that sampled and measured their optical and chemical properties. The particle composition was characterized by organic species with high OC/EC ratios (10–20), with water-soluble organic carbon (WSOC) and levoglucosan (Lev) comprising the largest fraction, up to 30 and 9%, respectively, of the OC. Aliphatic, aromatic, carbonyl, and carboxylate functionalities in the underground smoke were enriched by nitro compounds, and brown carbon (BrC) was identified by a high Absorption Angstrom Exponent (AAE) of 4.1. Organic “tar balls” in the peat smoke were more abundant (78.5%) than individual Ca-rich (e.g., Ca-oxides or carbonates), Fe-rich (e.g., Fe-oxides), and Al-rich (e.g., alumosilicates) particles. Peat smoke plumes affected an urban site in Moscow in August 2014, with ambient PM10 mass loadings reaching up to 97 µg m–3 and OC, EC, and ionic species accounting for a large percentage of the total aerosol enhancement. With the transport of air masses from the peat bog region to Moscow, the OC/EC ratio and AAE reached peak values of 7 and 1.3, respectively. Levoglucosan served as a molecular marker of the impact of peat smoldering, approaching a maximum ambient concentration of 108 ng m–3. WSOC correlated well with Lev, indicating secondary organic aerosol (SOA) formation associated with peat burning emissions. Spectral absorbance features showed characteristics similar to peat burning and traffic source emissions during fire and non-fire related days, confirming the potential effect of transported peat smoke on air quality in megacities.

Keywords

Peat bog fires Biomass burning Chemical marker Organic carbon Functionalities


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