ИСТИНА

Aerosols significantly impact the regional environment, including climate change, specifically in periods of extensive biomass burning (BB). Emissions and properties of BB aerosols are highly source-dependent, depending on burning practice, combustion phase (open flaming vs. smoldering), and type of biomass. Quantification of BB emissions is in the focus of current research and abatement strategies, especially given that the impacts of BB on regional air quality in highly populated areas are remaining rather uncertain. This work reports the measurements during the dry seasons of 2013 in Son La Province, northwest Vietnam, and of 2015 in Ba Vi Province , Central Vietnam. We focus on physico-chemical properties of aerosols, affected by biomass burning activities from agricultural and domestic combustion sources. The comparative analysis of particle organic/inorganic composition is carried out by Fourier Transform IR (FTIR) spectroscopy. The characterization of near-source emissions from traditional burning activities (on-field burning and domestic cooking) as well as traffic emission is specifically conducted in order to identify the major functional groups in ambient smoke. Analysis of FTIR spectra of particles in on-field and cooking emissions demonstrate the prominent absorption bands are related to aliphatic C-C-H, acid carbonyl C(O)OH, non-acid carbonyl C=O and carboxylate carbonyl RC(O)O groups. Asymmetric N–O stretches in nitro compounds as well as hydroxyl C-OH groups can be noted as specific features of on-field smoldering emission. Сooking emission is found additionally rich by ammonium NH42-, aromatic C=C-H, and Ar–NO2. FTIR spectra of on-road emission demonstrates the spectral absorption by aliphatic C-C-H in alkanes, and aromatic C=C as the functional markers of gasoline exhaust. The prominent absorption bands of acid and non-acid carbonyls, carboxylates, and aliphatic carbon during the whole BB period are similar to those in the on-field and cooking emissions. The band of ammonium is prominent in ambient aerosols. The bands of C-N-H in amines on days of low smoke can be assigned to biogenic functional groups, and were consequently absent in high smoke periods. The absorption bands of sulfates are identified in coarse particles. The relative concentrations of NH4+, aliphatic C-C-H, carbonyl C=O and C(O)O, carboxylate RC(O)O, CO3-, and SO42- in size-segregated ambient aerosols (PM 2.5, PM 1-2.5, PM 2.5-10) are classified at low, moderate, and high smoke levels, with respect to the evolution of aerosol chemistry from the BB emission sources into the ambient atmosphere. In PM2.5 all organic functionalities increase throughout the study period. Conversely, the relative concentrations of ammonium are not well correlated with the smoke intensity, indicating regional source influence other than from BB. Relative concentrations of carbonates are increasing from low to high smoke, and hence, showing the impact of re-suspended soil particles during intensive agricultural fires on the composition of coarse ambient aerosols. Finally, this work allows the decreasing the uncertainties in chemical identity of combustion particulate emissions in periods of extensive biomass burning and quantification of their environmental effects.