Abstract
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.
Highlights
Boreal ecosystems store a large amount of carbon, about one-fifth to one-third of the terrestrial organic carbon, in peat bogs that is partly released into the atmosphere during frequent fires, and renders peatlands as an important source of hazardous smoke (Levine, 1999; Langmann and Graf, 2003), which considerably affects ecosystems and carbon cycling (Turetsky et al, 2015)
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
water-soluble organic carbon (WSOC) correlated well with Lev, indicating secondary organic aerosol (SOA) formation associated with peat burning emissions
Summary
Boreal ecosystems store a large amount of carbon, about one-fifth to one-third of the terrestrial organic carbon, in peat bogs that is partly released into the atmosphere during frequent fires, and renders peatlands as an important source of hazardous smoke (Levine, 1999; Langmann and Graf, 2003), which considerably affects ecosystems and carbon cycling (Turetsky et al, 2015). In Siberia, four million hectares of peatlands were burned on average each year between 1975 and 2005, with the fire frequency doubling since the 1990s (Sheng et al, 2004). Intensive peat fires in regions of high population, such as the European part of Russia, affect the air quality in large cities. During the peat bog burning event in 2002 a significant weakening of solar radiation was observed in Popovicheva et al, Aerosol and Air Quality Research, 19: 484–503, 2019 the megacity Moscow, when the visibility dropped to 50– 300 meters (Chubarova et al, 2011). Smoke advected from burning peatlands pervaded Moscow city for several weeks, leading to a doubling of the natural mortality rate (Barriopedro et al, 2011)
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