Bc Source Apportionment - MAGEE Scientific Aethalometer AE33 User Manual

Aethalometer
Model AE33

11.2.4 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
and λ spectral dependencies, respectively (Sandradewi 2008). The exponents which describe
-2
the spectral dependence are called Ångström exponents: α
biomass. We get the following equations:
( 470⁡���� )
��
������ ����
( 950⁡���� )
��
������ ����
( 470⁡���� )
��
������ ����
( 950⁡���� )
��
������ ����
( 470⁡���� ) = ��
��
������
( 950⁡���� ) = ��
��
������
where b (λ) is absorption coefficient, λ is wavelength, b
abs
b (λ) a biomass burning fraction of absorption coefficient. Portion of biomass burning
abs bb
BB(%) is:
��
������
���� ( % ) =
��
������
Biomass burning and traffic BC fractions are then calculated as:
���� = ���� ∗ ����
����
= ( 1 − ���� ) ∗ ����
����
����
____________________________________________________________________________________________________________
User's manual – Ver. 1.55
−��
����
470
= ( )
,
950
−��
����
470
= ( )
,
950
( 470⁡���� )
������ ����
( 950⁡���� )
������ ����
( 950⁡���� )
����
.
( 950⁡���� )
,
.
=1 for fossil fuel and α
ff
( 470⁡���� )
+ ��
������ ����
( 950⁡���� )
+ ��
������ ����
(λ)
abs
July 2017
bb
,
,
a fossil fuel fraction and
ff
-1
=2 for
110/146