Chemical, physical, and optical evolution of biomass burning aerosols: a case study

Abstract

Abstract. In-situ chemical composition measurements of ambient aerosols have been used for characterizing the evolution of submicron aerosols from a large anthropogenic biomass burning (BB) event in Israel. A high resolution Time of Flight Aerosol Mass Spectrometer (HR-RES-TOF-AMS) was used to follow the chemical evolution of BB aerosols during a night-long, extensive nationwide wood burning event and during the following day. While these types of extensive BB events are not common in this region, burning of agricultural waste is a common practice. The aging process of the BB aerosols was followed through their chemical, physical and optical properties. Mass spectrometric analysis of the aerosol organic component showed that aerosol aging is characterized by shifting from less oxidized fresh BB aerosols to more oxidized aerosols. Evidence for aerosol aging during the day following the BB event was indicated by an increase in the organic mass, its oxidation state, the total aerosol concentration, and a shift in the modal particle diameter. The effective broadband refractive index (EBRI) was derived using a white light optical particle counter (WELAS). The average EBRI for a mixed population of aerosols dominated by open fires was m = 1.53(±0.03) + 0.07i(±0.03), during the smoldering phase of the fires we found the EBRI to be m = 1.54(±0.01) + 0.04i(±0.01) compared to m = 1.49(±0.01)+0.02i(±0.01) of the aged aerosols during the following day. This change indicates a decrease in the overall aerosol absorption and scattering. Elevated levels of particulate Polycyclic Aromatic Hydrocarbons (PAHs) were detected during the entire event, which suggest possible implications for human health during such extensive event.

Spectral absorption of biomass burning aerosol determined from retrieved single scattering albedo during ARCTAS

“…3, UV SSA values are nearly identical for the two cases while visible SSA is higher for the aged 17 April plume. A similar "brightening" at visible wavelengths with age was observed in field studies of biomass burning aerosol (Abel et al, 2003;Adler et al, 2011). Thus, the increase in AAE with plume age observed here is largely due to the decrease in absorption at visible wavelengths with time.…”

“…These findings may suggest that the oxidation of biomass burning OA primarily influences aerosol optical properties in the visible. This may, in part, be related to observed increases in particle size (and thus increased scattering at visible wavelengths) with age due to coagulation, water uptake, and condensation of gases (e.g., Grieshop et al, 2009a;Adler et al, 2011;Kondo et al, 2011), however changes to OA chemistry on a molecular level may also play a role. The similar UV SSA values between the aged 17 April plume and the fresh 29 June plume suggests similar amounts of UV absorption due to aerosols can be expected in fresh and aged plumes.…”

Aged boreal biomass-burning aerosol size distributions from BORTAS 2011

“…Quantifying the natural variations in biomass-burning aerosols is therefore necessary for accurate predictions. Previous studies of field and lab experiments show biomass-burning size distributions vary according to plume age, combustion phase, and fuel type (Adler et al, 2011;Capes et al, 2008;Hobbs et al, 2003;Hosseini et al, 2010;Janhäll et al, 2010;Okoshi et al, 2014). A review of observed size-distribution data by Janhäll et al (2010) shows the differences in modal width and median diameter as a function of fuel type (forest, savannah, grass), modified combustion efficiency, and plume age (fresh versus aged).…”

Source Apportionment of Urban Particulate Matter using Hourly Resolved Trace Metals, Organics, and Inorganic Aerosol Components

“…These results suggest that during the forest fire event, the Oxidised Organics factor represented aerosol mass from the Biomass Burning factor that had 5 been processed through photochemical aging. Adler et al (2011) reported an OOA factor with a high F44 during a day following a massive forest fire event due to further oxidation processes. Furthermore, the organic signal profile of the Oxidised Organics factor in this study was highly comparable to the mass spectrum profile of the OOA-BB factor previously observed during a massive forest fire event in summer (Bougiatioti et al, 2014).…”