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Title:
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Sampling of PM10 at high relative humidity
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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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1-4-2000
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ECN report number:
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Document type:
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ECN-C--00-061
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ECN publication
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Number of pages:
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Full text:
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17
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Download PDF
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Abstract:
PM10 contains hygroscopic components which attract water. Due to thiswater uptake particles which actually belong to PM10 may become so large that
they are not collected in PM10 sampling. This loss is not considered in
calculations of the PM10 concentration, which leads to an overestimate of the
modeled PM10. The Netherlands Energy Research Foundation (ECN) was asked to
identify the major factors influencing the hygroscopic growth of PM10 in the
Netherlands and to provide an estimate of the loss in sampling of PM10 at
high relative humidities. It was found that the dominant hygroscopic aerosol
components in the Netherlands are sulfate/nitrate and sea salt. Sulfate and
nitrate (in the form of ammonium sulfate and ammonium nitrate) are typically
present in particles with a dry diameter smaller than 2.5 mum. Such small
particles only grow to droplets with a size larger than 10 mum in
situations with fog. It is shown that the non-hygroscopic material should
also be present in the fog-droplets. This means that most PM is not sampled
during fog. With the given frequency of fog in the Netherlands, this leads to
the estimate that on an annual basis of 5% of PM10 is missed during sampling.
Since PM10 values are expected to be high on foggy days, much larger
differences between modeled and measured peak values of PM10 are projected.
Little sea salt will be missed in PM10 sampling, because it is not present in
fog/sea mist. 8 refs.
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