|
Title:
|
|
Throughfall monitoring during one year at 14 ICP forest level 2 sites in The Netherlands
|
|
|
|
Author(s):
|
|
|
|
|
|
Published by:
|
Publication date:
|
|
ECN
|
1997
|
|
|
|
ECN report number:
|
Document type:
|
|
ECN-C--97-090
|
ECN publication
|
|
|
|
Number of pages:
|
Full text:
|
|
45
|
Download PDF
|
Abstract:
During one year throughfall composition was monitored at 14 ICP ForestLevel II sites in the Netherlands. The aim of this research was to estimate
the atmospheric deposition at the sites and to compare the results with
measurements made by the University of Nijmegen in Nijmegen, Netherlands,
nine years ago to determine the influence of abatement strategies so far. In
order to estimate atmospheric deposition a canopy budget model was applied.
Wet deposition measurements were obtained from the national monitoring
network run by RIVM. The average total nitrogen deposition to the 14 stands
was 3080 mol/ha/a, whereas the average potential acid deposition amounted to
4600 mol/ha/a. Dry deposition made up about 75% of the total deposition.
Model estimates agreed reasonably well with measurements, except for three
locations. At Smilde, Netherlands, the throughfall flux was much higher,
probably due to the soil conditions. At Ulvenhout, Nethrlands, the measured
flux was lower than the model results. This is mainly due because of the poor
quality of the measurements at this site as the result of vandalism, forest
management and recreation. At the third Dutch location (Zeist) measurements
were also lower than model results, which could not be explained. The
measurements show that the pollution gradient has changed during the past
years. There used to be a clear gradient from south to the north of the
country, with decreasing fluxes of nitrogen and potential acid. No such
strong gradient could be obtained from our measurements. It is impossible to
derive conclusions about the abatement strategies by comparing the
throughfall data made nine years ago and those presented here. The
uncertainty in the data is too large and the difference in meteorological
conditions between the years dominate the observed changes in deposition. In
1986 the precipitation was about a factor two higher than that in the period
October 1995 - October 1996. The throughfall fluxes were therefore also a
factor two higher. Time-series of throughfall measurements and micro
meteorological measurements made at Speulder forest, Netherlands, between
1987 and 1996 show that the sulphur deposition decreased, but that the
nitrogen deposition remained about the same. It is useful to repeat the
measurements annually to monitor the effect of abatement strategies, because
it is the only method which provides deposition estimates against relatively
low costs. However, several conditions have to be fulfilled. The samplers
must remain in the same position for several years, the method should be the
most accurate, the method should be tested continuously against micro
meteorological measurements such as those conducted at Speulder forest and
the interpretation should be done together with a deposition model. The
deposition model is tested with the measurements to see if the model
parameters have been changed. The number of sites can be limited and should
represent the gradient over the country and some tree species. 6 figs., 8
tabs., 19 refs., 1 appendix
Back to List