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Composition/size of the light-scattering aerosol in the Netherlands
Gepubliceerd door: Publicatie datum:
ECN 1996
ECN publicatienummer: Publicatie type:
ECN-RX--96-037 Overig
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27  Niet beschikbaar.

In 1992, 1993 and 1994 the size/composition of the aerosol in TheNetherlands has been measured in several measuring campaigns. The aim of the study was the characterisation of those anthropogenic particles which most effectively scatter short-wave solar radiation. Since the largest effect of aerosol on radiation was expected at the times with the highest radiative flux, the measurements were made in the summer half-year around noon and under sunny conditions. Aerosol in arctic marine air served as the reference background. It contained as little as 0.1 mug/m3 nitrate and non-seasalt sulfate. In continental air some 75% of the aerosol mass was submicron. Ammonium nitrate and ammonium sulfate were the dominant (anthropogenic) aerosol species in the size range with maximum light-scattering (0.4 to 1.0 mum) and, with values up to 25 mug/m3, almost completely of a manmade origin. The ammonium nitrate concentrations were as high as or higher than those of ammonium sulfate, while the concentration of ammonium nitrate may have been underestimated because of evaporative losses during collection, of which examples are given. The sulfate size distribution did not depend on the sulfate concentration and the present distribution is very similar to that in the period 1982 to 1984, which is evidence of stability of the distribution over time. Almost half of the submicron aerosol in the relevant size range could not be identified. Elemental carbon contributed only an estimated 10% to this mass and the submicron dust content was even smaller. It was thus concluded by inference that most of the unidentified material was organic carbon. In marine air advected over the UK the submicron aerosol was manmade. In the particles, which most effectively scatter solar radiation, manmade natural seasalt-chloride is substituted by sulfate. This substitution changes the aerosol (radiative) properties: laboratory investigations, performed as part of this study, showed that the sodium sulfate is a water-free crystal, while the original seasalt aerosols are metastable saline droplets. 4 figs., 1 tab., 18 refs.

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