Rapport in het kort
A micrometeorological gradient method has been applied
to monitor SO2 dry deposition fluxes on a routine basis. Results of a
feasibility study during 1987 to 1989 at a rural site in the Netherlands
demonstrated that this method can be used to measure dry deposition flux and
deposition velocity of SO2 directly and that routine application in a
monitoring station is possible. However, about 76% of the collected
measuring cycles (36 - 39 minutes) had to be rejected for flux calculations
due to fluctuations in turbulence intensities, low concentration levels and
instrument failures. From the data a clear diurnal pattern was found for
the flux and deposition velocity. A yearly average flux of 22 kg SO2
ha-1y-1, an average deposition velocity of 0.7 cm s-1 were obtained. A
strong relation between deposition velocity and wind speed was found,
indicating that the deposition is controlled by aerodynamic properties. The
measurements suggest very low surface resistance values due to surface
wetness in an alkaline agricultural environment. The uncertainty in surface
resistance was found to be very large.
