3 research outputs found
Fossil and Nonfossil Sources of Organic and Elemental Carbon Aerosols in the Outflow from Northeast China
Source
quantification of carbonaceous aerosols in the Chinese outflow
regions still remains uncertain despite their high mass concentrations.
Here, we unambiguously quantified fossil and nonfossil contributions
to elemental carbon (EC) and organic carbon (OC) of total suspended
particles (TSP) from a regional receptor site in the outflow of Northeast
China using radiocarbon measurement. OC and EC concentrations were
lower in summer, representing mainly marine air, than in other seasons,
when air masses mostly traveled over continental regions in Mongolia
and northeast China. The annual-mean contribution from fossil-fuel
combustion to EC was 76 Ā± 11% (0.1ā1.3 Ī¼g m<sup>ā3</sup>). The remaining 24 Ā± 11% (0.03ā0.42 Ī¼g
m<sup>ā3</sup>) was attributed to biomass burning, with slightly
higher contribution in the cold period (ā¼31%) compared to the
warm period (ā¼21%) because of enhanced emissions from regional
biomass combustion sources in China. OC was generally dominated by
nonfossil sources, with an annual average of 66 Ā± 11% (0.5ā2.8
Ī¼g m<sup>ā3</sup>), approximately half of which was apportioned
to primary biomass-burning sources (34 Ā± 6%). In winter, OC almost
equally originated from primary OC (POC) emissions and secondary OC
(SOC) formation from fossil fuel and biomass-burning sources. In contrast,
summertime OC was dominated by primary biogenic emissions as well
as secondary production from biogenic and biomass-burning sources,
but fossil-derived SOC was the smallest contributor. Distinction of
POC and SOC was performed using primary POC-to-EC emission ratios
separated for fossil and nonfossil emissions
Source Identification and Apportionment of Halogenated Compounds Observed at a Remote Site in East Asia
The sources of halogenated compounds
in East Asia associated with
stratospheric ozone depletion and climate change are relatively poorly
understood. High-precision in situ measurements of 18 halogenated
compounds and carbonyl sulfide (COS) made at Gosan, Jeju Island, Korea,
from November 2007 to December 2011 were analyzed by a positive matrix
factorization (PMF). Seven major industrial sources were identified
from the enhanced concentrations of halogenated compounds observed
at Gosan and corresponding concentration-based source contributions
were also suggested: primary aluminum production explaining 37% of
total concentration enhancements, solvent usage of which source apportionment
is 25%, fugitive emissions from HCFC/HFC production with 11%, refrigerant
replacements (9%), semiconductor/electronics industry (9%), foam blowing
agents (6%), and fumigation (3%). Statistical trajectory analysis
was applied to specify the potential emission regions for seven sources
using back trajectories. Primary aluminum production, solvent usage
and fugitive emission sources were mainly contributed by China. Semiconductor/electronics
sources were dominantly located in Korea. Refrigerant replacement,
fumigation and foam blowing agent sources were spread throughout East
Asian countries. The specified potential source regions are consistent
with country-based consumptions and emission patterns, verifying the
PMF analysis results. The industry-based emission sources of halogenated
compounds identified in this study help improve our understanding
of the East Asian countriesā industrial contributions to halogenated
compound emissions
Source Forensics of Black Carbon Aerosols from China
The
limited understanding of black carbon (BC) aerosol emissions
from incomplete combustion causes a poorly constrained anthropogenic
climate warming that globally may be second only to CO<sub>2</sub> and regionally, such as over East Asia, the dominant driver of climate
change. The relative contribution to atmospheric BC from fossil fuel
versus biomass combustion is important to constrain as fossil BC is
a stronger climate forcer. The source apportionment is the underpinning
for targeted mitigation actions. However, technology-based ābottom-upā
emission inventories are inconclusive, largely due to uncertain BC
emission factors from small-scale/household combustion and open burning.
We use ātop-downā radiocarbon measurements of atmospheric
BC from five sites including three city sites and two regional sites
to determine that fossil fuel combustion produces 80 Ā± 6% of
the BC emitted from China. This source-diagnostic radiocarbon signal
in the ambient aerosol over East Asia establishes a much larger role
for fossil fuel combustion than suggested by all 15 BC emission inventory
models, including one with monthly resolution. Our results suggest
that current climate modeling should refine both BC emission strength
and consider the stronger radiative absorption associated with fossil-fuel-derived
BC. To mitigate near-term climate effects and improve air quality
in East Asia, activities such as residential coal combustion and city
traffic should be targeted