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| Titel |
What do we learn from EC (black carbon), OC and their Isotope Measurements in Fine Airborne PM over Canada? |
| VerfasserIn |
L. Huang, W Zhang, S. Sharma, J. Brook, T. Chan, R. Leaitch |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029701
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| Zusammenfassung |
| Elemental carbon and organic carbon (EC & OC) components in fine airborne carbonaceous
particulate matter (PM) are major air pollutants existing in urban, rural and remote
environments as well as key players in climate change (via radiative forcing). It
is known that both EC (also called as black carbon or soot) and OC are released
from various emission sources (e.g., fossil fuel combustion, biomass burning) and
OC is also produced in the atmosphere through photochemical oxidations from
gas phase organics. Tracking their spatial (e.g., from urban to rural to background
air or latitudinal) and temporal (e.g. seasonal and inter-annual) distributions will
provide valuable information to constraining emission sources and atmospheric
transport/transformation mechanisms as well as to assessing effectiveness of mitigation for
these pollutants.
Sources/processes detecting and attributing are key aspects in both air quality and climate
change research. Isotope measurements, as independent tools, can provide valuable insight
to constrain those aspects. Duo to its inert nature, it is expected that the δ13C of
EC won’t be changed after emitting to the atmosphere, reflecting the signature
of source, whereas the δ13Cof OC will have a various degree of changes through
photochemical processes, depending on the history of the air mass. Therefore, an isotopic
profile of δ13C in carbon components released at different temperature ranges can
provide useful insight to the emission sources and formation processes in ambient
PM.
Quartz filter samples were collected at the five sites over Canada, from Toronto (a typical
urban site), Egbert (a rural site, ~ 80 km northwest of Toronto), to Fraserdale, and Berm-TT
(both are continental boreal forest sites), to Alert (an Arctic baseline site). EC and OC
concentrations for those samples collected during the period (2006 - 2007) were determined
using a thermal method (Totoal_900_EnCan) developed in Toronto lab at Environment
Canada, which is different from IMPROVE and NIOSH. The magnitude of POC (pyrolized
organic carbon), which is produced in the analysis and proportional to oxygenated OC on the
filters, was also obtained from these measurements. A subset of the samples was selected for
δ13C measurements in each carbon fraction (i.e., OC, POC and EC). Due to the collocated
filter sampling with the in situ measurements of aerosol optical properties and CO2
concentrations, the relationship between the annual mean EC/OC concentrations and aerosol
light absorption and scattering as well as between the EC and excess CO2 (i.e.
CO2 difference relative to a background value) on a regional scale have been also
investigated.
Combining the isotopic measurements, it is found that the spatial gradients of EC and OC
during different seasons from urban, rural to background air over Canada were mainly
due to the transport of human induced emissions although biomass burning and
biogenic emissions, as primary sources, and atmospheric photochemical oxidations, as
secondary sources, play important roles in influencing seasonal variations at the
different sites. EC and OC are major components contributing to the aerosols optical
properties on a regional scale. Integrating EC/OC in fine PM with CO2 and their δ13C
measurements will be a powerful tool to study human-induced impact on climate change. |
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