A VARIABLE-RESOLUTION TRANSPORT MODEL APPLIED FOR NHX IN EUROPE

The statistical atmospheric transport model TREND has been applied for the calculation of concentrations and depositions of ammonia (NH3) and ammonium (NH4+). The model is capable of describing dispersion, conversion and deposition from both local sources (necessary to obtain good results for NH3) and from more distant sources (necessary to obtain good results for NH4+). Model results show that in western Europe 44% of the emitted NH3 from a 1 m high source is dry deposited as NH3, 6% is wet deposited as the contribution of NH3 to the wet deposition of NH(x), 14% is dry deposited as NH4+ and 36% is wet deposited as the contribution of NH4+ to the wet deposition of NH(x). The model results agree well with measured NH3 and NH4+ concentrations-the latter in both aerosol form and precipitation-in The Netherlands, Belgium, Denmark, the U.K., the F.R.G., Sweden and other parts of Europe. Vertical concentration profiles of NH3 and NH4+ at Cabauw, The Netherlands are also reproduced well, as well as the diurnal variation of the NH3 concentration at Elspeetsche Veld, The Netherlands.