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. Starting in March 2014 and lasting until late summer, the Tver region, north of Moscow city, was considerably affected by long-lasting peat bog fires. Peat bog smoldering emissions from three types of smoke (underground, inside and above grass) were analyzed by an extensive suite of instrumentation that sampled and measured their optical and chemical properties. 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%, of OC, respectively. Aliphatic, aromatic, carbonyl, and carboxylate functionalities in underground smoke were enriched by nitro compounds. Brown carbon (BrC) was identified by a high Absorption Angstrom Exponent (AAE) of 4.1. Organic “tar balls” in peat smoke were most abundant (78.5%) in comparison with Ca-rich (e.g., Ca-oxides, carbonates), Fe-rich (e.g., Fe-oxides), and Al-rich (e.g., alumosilicates) individual particles. Peat smoke plumes affected an urban site in Moscow city in August 2014, with ambient PM10 mass loadings reaching up to 97 µg m-3 while OC, EC and ionic species accounted for a large percentage of the total aerosol enhancement. During air mass transport from the peat bog region to Moscow city, OC/EC ratios and AAE reached peak values of 7 and 1.3, respectively. Levoglucosan served as a molecular marker of peat smoldering impact, approaching maximum ambient concentrations of 108 ng m-3. WSOC correlated well with Lev, demonstrating 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 impact of peat smoke transport on air quality in a megacity.