TY - DATA T1 - Limitation of the Use of the Absorption Angstrom Exponent for Source Apportionment of Equivalent Black Carbon: a Case Study from the North West Indo-Gangetic Plain PY - 2016/01/19 AU - Saryu Garg AU - Boggarapu Praphulla Chandra AU - Vinayak Sinha AU - Roland Sarda-Esteve AU - Valerie Gros AU - Baerbel Sinha UR - https://acs.figshare.com/articles/journal_contribution/Limitation_of_the_Use_of_the_Absorption_Angstrom_Exponent_for_Source_Apportionment_of_Equivalent_Black_Carbon_a_Case_Study_from_the_North_West_Indo_Gangetic_Plain/2086231 DO - 10.1021/acs.est.5b03868.s001 L4 - https://ndownloader.figshare.com/files/3719449 KW - source KW - biomass combustion plumes KW - biomass combustion KW - aethalometer filter tape KW - contribution KW - PM 2.5 aerosol KW - absorption angstrom exponent KW - Equivalent Black Carbon KW - α abs KW - Absorption Angstrom Exponent KW - BCeq mass N2 - Angstrom exponent measurements of equivalent black carbon (BCeq) have recently been introduced as a novel tool to apportion the contribution of biomass burning sources to the BCeq mass. The BCeq is the mass of ideal BC with defined optical properties that, upon deposition on the aethalometer filter tape, would cause equal optical attenuation of light to the actual PM2.5 aerosol deposited. The BCeq mass hence is identical to the mass of the total light-absorbing carbon deposited on the filter tape. Here, we use simultaneously collected data from a seven-wavelength aethalometer and a high-sensitivity proton-transfer reaction mass spectrometer installed at a suburban site in Mohali (Punjab), India, to identify a number of biomass combustion plumes. The identified types of biomass combustion include paddy- and wheat-residue burning, leaf litter, and garbage burning. Traffic plumes were selected for comparison. We find that the combustion efficiency, rather than the fuel used, determines αabs, and consequently, the αabs can be ∼1 for flaming biomass combustion and >1 for older vehicles that operate with poorly optimized engines. Thus, the absorption angstrom exponent is not representative of the fuel used and, therefore, cannot be used as a generic tracer to constrain source contributions. ER -