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ECN publication
Aerosol light-scattering in The Netherlands
Published by: Publication date:
ECN 1995
ECN report number: Document type:
ECN-RX--95-044 Other
Number of pages: Full text:
32 Download PDF  

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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