English Abstract In this report results of the additional monitoring
programme on NH3 are reported. The aim of this project was to evaluate long
range transport model (TREND) results on NH3 concentrations in high density
emission areas. For this evaluation, continuous ammonia concentrations were
measured during one year at two locations in the Netherlands (Vredepeel and
Lunteren). Furthermore, the representativeness of these fixed point
measurements was investigated using mobile measurements and a short
term/short range transport model for NH3 (SLAM). The measuring strategy
developed for this research provides a good tool for estimating the
representativeness of a single point measurement for a larger area
surrounding the fixed-point. The results using the SLAM model agree
reasonably well with measured concentrations in time and space, provided
that data are selected for wind speed > 1.5 m.s-1. In comparing model
results with measurements the greatest uncertainty results from emission
estimates and temporal variation in emissions. The uncertainty in the
annual average concentrations obtained at the fixed-point is estimated at
20-25%. The Vredepeel fixed-point is representative within 10% in
comparison with the surrounding 5 x 5 km area. Due to a lack of
measurements at the Lunteren fixed-point no final statement can be made for
this area, although measurements and SLAM calculations show 30-40% higher
concentrations in comparison with the 5 x 5 km grid. TREND calculations
show 30-40% variation in using different meteorological data (national or
local), emission estimates and temporal variations in emission. The final
conclusion of this research is that there is no significant difference
between TREND results and yearly average measured concentrations for high
ammonia emission areas. Hereby the measured concentration should be
evaluated on representativeness for a surrounding 5 x 5 km area and local
meteorology and the best guess on emissions should be used as input for
TREND calculations.
