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Assessment of biomass burning and fossil fuel contribution to black carbon concentrations in Delhi during winter.

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Title: Assessment of biomass burning and fossil fuel contribution to black carbon concentrations in Delhi during winter.
Authors: Dumka, U.C.1, Kaskaoutis, D.G.1,2 dkask@meteo.noa.gr, Tiwari, S.3, Safai, P.D.4, Attri, S.D.5, Soni, V.K.5, Singh, N.1, Mihalopoulos, N.2,6
Source: Atmospheric Environment. Dec2018, Vol. 194, p93-109. 17p.
Subject Terms: *Biomass burning, *Fossil fuels, *Soot, *Combustion, Pyrography
Abstract: Abstract This study aims to assess the contribution of fossil-fuel combustion (BC ff) and biomass (or wood) burning (BC wb) to wintertime black carbon (BC) concentrations in Delhi using the "Aethalometer model" approach. Continuous measurements using 7-wavelength Aethalometer (AE-33) were taken from December 2015 to February 2016 in Delhi downtown, as part of a multi-instrument research campaign, revealing high BC concentrations of 24.4 ± 12.2 μg m−3 (range from 3.2 to 59.9 μg m−3). The BC ff contribution dominates with an average fraction of 72% at 880 nm, indicating an important contribution from biomass burning (28%). The daily-averaged Absorption Ångström Exponent (AAE 370-880) varies between 1.08 and 1.46 due to changes in the BC emission rates, variations in the relative strength between fossil-fuel and wood-burning sources and mixing processes in the atmosphere. The average BC ff /BC wb ratio is estimated as 2.90 ± 1.47 at 880 nm, while the BC wb contribution maximized in the evening hours due to enhanced wood burning for heating. The BC, BC ff and BC wb concentrations exhibit remarkable diurnal variations with maximum values in the morning and evening/night hours and lower around noon, primarily driven by changes in the mixing-layer height. The highest BC, BC ff and BC wb concentrations are associated with weak winds (<2 ms−1), revealing a dominance of local emission sources within the Delhi metropolitan area. A sensitivity analysis is performed by changing the wavelength pairs and the pre-assumed AAE values in order to evaluate the stability of the "Aethalometer model" in assessment of the BC source apportionment. The results reveal that the "Aethalometer model" is more sensitive in estimating the BC wb , while the changes in the BC ff component are rather low. Graphical abstract Image 1 Highlights • Daily-mean BC concentrations range from 3.2 to 59.9 μg m−3 in Delhi during winter. • The BC ff vs BC wb estimations are 72% vs 28% at 880 nm. • Dependence of BC ff and BC wb on AAE ff and AAE wb values (Aethalometer model). • Higher BC ff /BC during early morning, higher BC wb /BC in the evening. • Boundary-layer dynamics control the BC concentrations. [ABSTRACT FROM AUTHOR]
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Abstract:Abstract This study aims to assess the contribution of fossil-fuel combustion (BC ff) and biomass (or wood) burning (BC wb) to wintertime black carbon (BC) concentrations in Delhi using the "Aethalometer model" approach. Continuous measurements using 7-wavelength Aethalometer (AE-33) were taken from December 2015 to February 2016 in Delhi downtown, as part of a multi-instrument research campaign, revealing high BC concentrations of 24.4 ± 12.2 μg m−3 (range from 3.2 to 59.9 μg m−3). The BC ff contribution dominates with an average fraction of 72% at 880 nm, indicating an important contribution from biomass burning (28%). The daily-averaged Absorption Ångström Exponent (AAE 370-880) varies between 1.08 and 1.46 due to changes in the BC emission rates, variations in the relative strength between fossil-fuel and wood-burning sources and mixing processes in the atmosphere. The average BC ff /BC wb ratio is estimated as 2.90 ± 1.47 at 880 nm, while the BC wb contribution maximized in the evening hours due to enhanced wood burning for heating. The BC, BC ff and BC wb concentrations exhibit remarkable diurnal variations with maximum values in the morning and evening/night hours and lower around noon, primarily driven by changes in the mixing-layer height. The highest BC, BC ff and BC wb concentrations are associated with weak winds (<2 ms−1), revealing a dominance of local emission sources within the Delhi metropolitan area. A sensitivity analysis is performed by changing the wavelength pairs and the pre-assumed AAE values in order to evaluate the stability of the "Aethalometer model" in assessment of the BC source apportionment. The results reveal that the "Aethalometer model" is more sensitive in estimating the BC wb , while the changes in the BC ff component are rather low. Graphical abstract Image 1 Highlights • Daily-mean BC concentrations range from 3.2 to 59.9 μg m−3 in Delhi during winter. • The BC ff vs BC wb estimations are 72% vs 28% at 880 nm. • Dependence of BC ff and BC wb on AAE ff and AAE wb values (Aethalometer model). • Higher BC ff /BC during early morning, higher BC wb /BC in the evening. • Boundary-layer dynamics control the BC concentrations. [ABSTRACT FROM AUTHOR]
ISSN:13522310
DOI:10.1016/j.atmosenv.2018.09.033