Environmental Science & Technology,
Journal Year:
2022,
Volume and Issue:
56(18), P. 12873 - 12885
Published: Sept. 9, 2022
The
light-absorbing
organic
aerosol
(OA)
constitutes
an
important
fraction
of
absorbing
components,
counteracting
major
cooling
effect
aerosols
to
climate.
mechanisms
in
linking
the
complex
and
changeable
chemistry
OA
with
its
properties
remain
be
elucidated.
Here,
by
using
solvent
extraction,
ambient
from
urban
environment
was
fractionated
according
polarity,
which
further
nebulized
online
characterized
compositions
properties.
Water
extracted
high-polar
compounds
a
significantly
higher
oxygen
carbon
ratio
(O/C)
than
methanol
extracts.
A
transition
O/C
about
0.6
found,
below
above
enhancement
reduction
absorptivity
were
observed
increasing
O/C,
occurring
on
less
polar
high
compounds,
respectively.
In
particular,
co-increase
nitrogen
elements
suggests
role
nitrogen-containing
functional
groups
enhancing
(e.g.,
forming
aromatics),
while
oxidation
(O/C
>
0.6)
likely
led
fragmentation
bleaching
chromophores.
results
here
may
reconcile
previous
observations
darkening
or
whitening
chromophores
brown
carbon,
parametrization
has
potential
link
changing
polarity
Atmospheric chemistry and physics,
Journal Year:
2021,
Volume and Issue:
21(19), P. 14851 - 14869
Published: Oct. 6, 2021
Abstract.
This
study
investigated
the
sources
of
black
carbon
(BC)
at
two
contrasting
urban
environments
in
Helsinki,
Finland:
residential
area
and
street
canyon.
The
measurement
campaign
was
conducted
winter–spring
2019,
whereas
canyon
measurements
were
carried
out
autumn
2015.
BC
explored
by
using
positive
matrix
factorization
(PMF)
for
organic
refractory
(rBC)
mass
spectra
collected
with
a
soot
particle
aerosol
spectrometer
(SP-AMS).
Based
on
PMF
analysis,
sites
had
different
local
sources;
largest
fraction
originated
from
biomass
burning
site
(38
%)
vehicular
emissions
(57
%).
Also,
size
distribution
diverged
as
traffic
found
∼100–150
nm
combustion
detected
∼300
nm.
At
both
sites,
large
associated
background
or
long-range-transported
indicated
high
oxidation
state
organics
related
to
those
factors.
results
analysis
compared
source
apportionment
Aethalometer
model
calculated
pairs
absorption
Ångström
values.
It
that
several
factors
can
be
attributed
wood
fossil
fuel
provided
model.
In
general,
showed
less
variation
between
within
day
than
PMF,
indicating
it
responsive
fast
changes
site,
could
not
distinguish
many
due
similar
optical
properties
sources.
this
increase
understanding
limitations
validity
methods
environments.
Moreover,
advances
current
knowledge
especially
contribution
areas.
Atmospheric chemistry and physics,
Journal Year:
2021,
Volume and Issue:
21(17), P. 12809 - 12833
Published: Aug. 31, 2021
Abstract.
Understanding
the
sources
of
light-absorbing
organic
(brown)
carbon
(BrC)
and
its
interaction
with
black
(BC)
other
non-refractory
particulate
matter
(NR-PM)
fractions
is
important
for
reducing
uncertainties
in
aerosol
direct
radiative
forcing.
In
this
study,
we
combine
multiple
filter-based
techniques
to
achieve
long-term,
spectrally
resolved,
source-
species-specific
atmospheric
absorption
closure.
We
determine
mass
efficiency
(MAE)
dilute
bulk
solutions
at
370
nm
be
equal
1.4
m2
g−1
fresh
biomass
smoke,
0.7
winter-oxygenated
(OA),
0.13
less
absorbing
OA.
apply
Mie
calculations
estimate
contributions
these
total
absorption.
While
enhanced
near-UV
has
been
traditionally
attributed
primary
here
show
that
anthropogenic
oxygenated
OA
may
equally
BrC
during
winter,
especially
an
urban
background
site.
demonstrate
insoluble
tar
balls
are
negligible
residential
burning
samples
study
thus
could
attribute
totality
NR-PM
shorter
wavelengths
methanol-extractable
BrC.
As
BC,
cross-section
(MAC)
fraction
independent
source,
while
observe
evidence
a
lensing
effect
associated
presence
components.
find
bare
BC
MAC
6.3
660
Ångström
exponent
0.93
±
0.16,
coatings
by
factor
∼
1.4.
Based
on
closure
between
observed
predicted
light
absorption,
provide
indication
suppression
The
reduction
remains
modest,
10
%–20
%
nm,
restricted
wavelengths,
where
significant.
Overall,
our
results
allow
assessment
relative
importance
different
aerosols
from
wide
range
ages.
When
integrated
solar
spectrum
300–900
found
contribute
around
two-thirds
radiation
carbonaceous
aerosols,
amplified
(with
interquartile
range,
IQR,
8
%–27
%),
IQR
6
%–13
(13
rural
site
winter).
Future
studies
will
directly
benefit
include
(a)
optical
modelling
aiming
understanding
profiles
complex
composed
BrC,
lensing-inducing
coatings;
(b)
source
apportionment
profiles;
(c)
global
quantifying
most
absorbers.
Environmental Science & Technology,
Journal Year:
2022,
Volume and Issue:
56(18), P. 12873 - 12885
Published: Sept. 9, 2022
The
light-absorbing
organic
aerosol
(OA)
constitutes
an
important
fraction
of
absorbing
components,
counteracting
major
cooling
effect
aerosols
to
climate.
mechanisms
in
linking
the
complex
and
changeable
chemistry
OA
with
its
properties
remain
be
elucidated.
Here,
by
using
solvent
extraction,
ambient
from
urban
environment
was
fractionated
according
polarity,
which
further
nebulized
online
characterized
compositions
properties.
Water
extracted
high-polar
compounds
a
significantly
higher
oxygen
carbon
ratio
(O/C)
than
methanol
extracts.
A
transition
O/C
about
0.6
found,
below
above
enhancement
reduction
absorptivity
were
observed
increasing
O/C,
occurring
on
less
polar
high
compounds,
respectively.
In
particular,
co-increase
nitrogen
elements
suggests
role
nitrogen-containing
functional
groups
enhancing
(e.g.,
forming
aromatics),
while
oxidation
(O/C
>
0.6)
likely
led
fragmentation
bleaching
chromophores.
results
here
may
reconcile
previous
observations
darkening
or
whitening
chromophores
brown
carbon,
parametrization
has
potential
link
changing
polarity
