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| Titel |
Micrometeorological flux measurements of aerosol and gases above Beijing |
| VerfasserIn |
Eiko Nemitz, Ben Langford, Neil Mullinger, Nicholas Cowan, Mhairi Coyle, William Joe Acton, James Lee, Pingqing Fu |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150330
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| Publikation (Nr.) |
 EGU/EGU2017-14777.pdf |
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| Zusammenfassung |
| Air pollution is estimated to cause 1.6 million premature deaths in China every year and in
the winter 2016/17 Beijing had to issue health alerts and put in place ad hoc limitations on
industrial and vehicular activity. Much of this pollution is attributed to emissions from
industrial processes and in particular coal combustion. By contrast, the diffuse pollutant
sources within the city are less well understood. This includes, e.g., emissions from the
Beijing traffic fleet, the sewage system, food preparation, solid fuel combustion in the streets
and small industrial processes.
Within the framework of a major UK-Chinese collaboration to study air pollution and its
impact on human health in Beijing, we therefore measured fluxes of a large range of
pollutants from a height of 102 m on the 325 m meteorological tower at the Institute of
Atmospheric Physics. Several instruments were mounted at 102 m: fluxes of CO2 and H2O
were measured with an infrared gas analyser (LiCOR 7500) and fluxes of ozone with a
combination of a relative fast-response ozone analyser (ROFI) and a 2B absolute
O3 instrument. Total particle number fluxes were measured with a condensation
particle counter (TSI CPC 3785), and size-segregated fluxes over the size range
0.06 to 20 μm with a combination of an optical Ultrafine High Sensitivity Aerosol
Spectrometer (UHSAS) and an Aerodynamic Particle Sizer Spectrometer (TSI
APS3321). Ammonia (NH3) fluxes were measured for the first time above the urban
environment using an Aerodyne compact quantum cascade laser (QCL). In addition,
composition resolved aerosol fluxes were measured with an Aerodyne Aerosol
Mass Spectrometer (HR-ToF-AMS), operated in a measurement container at the
bottom of the tower, which subsampled from a 120 m long copper tube (15 mm
OD).
The analysis so far suggests that, due to often low wind speeds, fluxes were at times
de-coupled from the surface. Fluxes normalised by CO2, a tracer for the amount of
fossil fuel consumed, should be less sensitive to transport effects. However, not
only fluxes, but also these CO2-ratioed fluxes are highly variable in both space
and time, indicating a complex mix of sources, which will be further investigated.
The organic aerosol fluxes were the largest we have recorded to date at any urban
measurement site. Nitrate, sulphate, chloride and ammonium all showed emissions
that followed a similar diurnal cycle as the organic aerosol. Much of this aerosol
is likely to have been formed by chemistry below the measurement height, but it
nevertheless indicates significant sources of the precursor gases within the footprint.
Comparing the measured fluxes of gas-phase NH3 and aerosol NH4+, at 102 m the
aerosol phase makes a significant contribution to the reduced nitrogen emission. |
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