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User's manual – Ver. 1.53 July 2015 60/75
5.8 BC source apportionment
Source apportionment of black carbon emissions is based on the Sandradewi et al. (2008)
model, with optical absorption coefficient being a sum of biomass burning and fossil fuel
burning fractions. Model is based on the difference in absorption coefficient wavelength
dependency assuming that absorption due to from fossil fuel and biomass emissions follow λ
-1
and λ
-2
spectral dependencies, respectively (Sandradewi 2008). The exponents which describe
the spectral dependence are called Ångström exponents: α
ff
=1 for fossil fuel and α
bb
=2 for
biomass. We get the following equations:
,
,
,
,
where b
abs
(λ) is absorption coefficient, λ is wavelength, b
abs
(λ)
ff
a fossil fule fraction and
b
abs
(λ)
bb
a biomass burning fraction of absorption coefficient. Portion of biomass burning
BB(%) is:
.
Biomass burning and traffic BC fractions are then calculated as:
,
.
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