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Title:
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Aerosol light-scattering in The Netherlands
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Author(s):
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Published by:
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Publication date:
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ECN
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1995
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ECN report number:
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Document type:
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ECN-RX--95-044
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Other
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Number of pages:
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Full text:
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32
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Download PDF
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Abstract:
The relation between the (midday) aerosol light-scattering and theconcentrations of nitrate and sulfate has been assessed at a site near the
coast of the North Sea in The Netherlands. Automated thermo-denuders were
used for the hourly measurement of the concentration of nitrate and sulfate
with a lower detection limit of 0.1 mug/m3. The site is operational since
October 1993. The first-year average dry aerosol light-scattering (at a
wavelength of 525 nm) was 0.71x10"-"4 m"-"1. In clean arctic marine air the
aerosol light-scattering was a factor of ten lower than the average value, in
polluted continental air it was up to a factor of ten higher. The ratio of
the total aerosol light-scattering to the concentration of sulfate was 20
m2/g. The contribution of nitrate to the aerosol light-scattering was
substantially higher than that of sulfate in the winter and of about equal
magnitude in the summer period. This is reflected in the ratio of the aerosol
light-scattering to the sum of the concentration of sulfate and nitrate being
9 m2/g in the summer and 7 m2/g in the winter. In November and December of
1993 the humidity dependence of the aerosol light-scattering was
investigated. Two types of (continental) aerosol were found with respect to
the humidity behaviour. One type showed a significant increase in
light-scattering at the deliquescence points of ammonium nitrate and ammonium
sulfate, with that of ammonium nitrate the most pronounced. The second type
of continental aerosol did not show deliquescence, but followed the typical
humidity dependence of aerosol in a supersaturated droplet state. In this
latter aerosol type, nitrate dominated over sulfate. It was concluded from
the study that the aerosol light-scattering in The Netherlands, in particular
its humidity dependence, is governed by (ammonium) nitrate. 10 figs., 22 refs.
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