Filter-based measurements of UV–vis mass absorption cross sections of organic carbon aerosol from residential biomass combustion: Preliminary findings and sources of uncertainty

Abstract

a b s t r a c tCombustion of solid biomass fuels is a major source of household energy in developing nations. Black (BC) and organic carbon (OC) aerosols are the major PM 2.5 (particulate matter with aerodynamic diameter smaller than 2.5 μm) pollutants co-emitted during burning of these fuels. While the optical nature of BC is well characterized, very little is known about the properties of light absorbing OC (LAOC). Here, we report the mass-based optical properties of LAOC emitted from the combustion of four commonly used solid biomass fuels-fuel-wood, agricultural residue, dung-cake, and mixed-in traditional Indian cookstoves. As part of a pilot field study conducted in central India, PM 2.5 samples were collected on Teflon filters and analyzed for their absorbance spectra in the 300-900 nm wavelengths at 1 nm resolution using a UV-Visible spectrophotometer equipped with an integrating sphere. The mean mass absorption cross-sections (MAC) of the emitted PM 2.5 and OC, at 550 nm, were 0.8 and 0.2 m 2 g À 1 , respectively, each with a factor of $ 2.3 uncertainty. The mean absorption Ångström exponent (AǺE) values for PM 2.5 were 3 7 1 between 350 and 550 nm, and 1.27 0.1 between 550 and 880 nm. In the 350-550 nm range, OC had an AǺE of 6.3 7 1.8. The emitted OC mass, which was on average 25 times of the BC mass, contributed over 50% of the aerosol absorbance at wavelengths smaller than 450 nm. The overall OC contribution to visible solar light (300-900 nm) absorption by the emitted particles was 26-45%. Our results highlight the need to comprehensively and accurately address: (i) the climatic impacts of light absorption by OC from cookstove emissions, and (ii) the uncertainties and biases associated with variability in biomass fuel types and combustion conditions, and filter-based measurement artifacts during determination of MAC values.

Aerosol emissions factors from traditional biomass cookstoves in India: insights from field measurements

“…Carbonaceous aerosol source profiles are useful for source apportionment, and they may also have implications for climate and health impact assessments. In a previous study (Pandey et al, 2016), we reported that light-absorbing OC may play a larger role in light absorption by cookstove emissions than that from earlier work on biomass burning in the USA. The difference in constituents of OC emissions from the two sources might contribute to the observed difference in their optical characteristics since thermal stability is known to be inversely related to the light absorption efficiency of organic compounds (Andreae and Gelencsér, 2006;Saleh et al, 2013).…”

Emission Characteristics of Primary Brown Carbon Absorption From Biomass and Coal Burning: Development of an Optical Emission Inventory for China

“…For bituminous coal, AAEs were similar for hv‐coal (1.19 ± 0.04) and lv‐coal (1.26 ± 0.04) emissions. These AAEs, all >1.0, suggest that particulate matter emitted from both crop residues and coal burning might contain BrC (X. Li et al, ; Pandey et al, ; Shen et al, ; J. Sun et al, ).…”

“…These AAEs, all >1.0, suggest that particulate matter emitted from both crop residues and coal burning might contain BrC (X. Pandey et al, 2016;Shen et al, 2016;J. Sun et al, 2017).…”

Quantifying black carbon light absorption enhancement with a novel statistical approach

“…MAE p of biomass burning (BB) samples is highly varied due to a wide range of fuel types and combustion conditions (Reid et al, 2005;Roden et al, 2006). A range from 6.1 to 80.8 m 2 g −1 was reported for BB MAE p at 550 nm (Pandey et al, 2016). Without the knowledge of source contributions, it is not feasible to derive a representative MAE p for E abs estimation.…”