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

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 PM 10 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.

Functional Factors of Biomass Burning Contribution to Spring Aerosol Composition in a Megacity: Combined FTIR-PCA Analyses

“…Black carbon (BC) produced by high-temperature combustion sources fit within the Rayleigh scattering regime for near-visible wavelengths with a theoretical λ −1 relationship [38]. Weak spectral dependence of ATN with AAE around 1 was found for diesel soot and urban aerosols produced by fossil fuels combustion [19], and as much as 4.1 for peat burning [39]. Spectral absorption of BB shows the combined impact of both BC absorbing from 670 nm down to 500 nm and brown carbon (BrC), which increases the absorption below 500 nm.…”

“…Therefore, for the purpose of this study, we used both spectral data for smoldering and flaming of regional BB as functional markers. To address agriculture fires relating to grass combustion, the inside and above grass burning spectra data were additionally considered, which were collected from the measurement campaign conducted during the peat burning event near Moscow [39].…”

A new lidar inversion method using a surface reference target applied to the backscattering coefficient and lidar ratio retrievals of a fog-oil plume at short range

“…Even if some models exist for the BRDF of surfaces (Bréon et al, 2002;Lobell and Asner, 2002;Mishchenko et al, 1999), their use seems difficult to implement because of the diversity of encountered surfaces during airborne measurements. Nevertheless, it may be possible to identify the reflectance of the ground surface by means of a spectroradiometer imager (Poutier et al, 2002;Miesch et al, 2005;Josset et al, 2018). The combination of these measurements with the herein proposed inversion method would a priori be complementary to establishing of new methods of calibration for down-looking lidar measurements (spaceborne or airborne lidars).…”

“…However, poor estimates of the reference or low signal-to-noise ratios (SNRs) can lead to severe uncertainties in the retrieved extinction and backscattering coefficients. Few sensitivity studies have been performed to evaluate such uncertainties (Matsumoto and Takeuchi, 1994;Rocadenbosch et al, 2012). Spatial averaging around the volume of reference in addition to time averaging is thus recommended to increase SNR.…”

Black carbon in spring aerosols of Moscow urban background

“…High anthropogenic emissions of PM in Moscow can occur due to traffic, industry, heating, waste recycling, and construction. Additionally, secondary aerosol formation and long transportation can impact the particulate loading and composition, as it was occurred during an extreme smoke events related to intensive wildfires near the city (Popovicheva et al 2014;Popovicheva et al 2019).…”