REDUCING THE CONTRIBUTION OF AMMONIA TO NITROGEN DEPOSITION ACROSS EUROPE

European emissions of reduced nitrogen, arising principally from agric ulture, are comparable with those of oxidised nitrogen from mobile and stationary combustion sources. It is therefore important to include a mmonia emissions in working towards a new protocol on nitrogen under t he programme of the UN Economic Commission for Europe on the control o f transboundary air pollution. However the nature of the sources and t he subsequent atmospheric transport and chemistry are very different f rom other acidifying pollutants. This paper describes work in hand und er the MARACCAS project to compare agricultural activities in differen t European countries and to assess the applicability and efficacy of p otential abatement measures. The aim is to derive abatement costs for each country relating successive emission reductions to the costs of a chieving them, to be used by the UN ECE Task Force on Integrated Asses sment Modelling (TFIAM) - in particular with our Abatement Strategies Assessment Model, ASAM. The paper will also address the large uncertai nties involved in integrated assessment modelling with respect to ammo nia, and suggest how these may be allowed for in deriving cost-effecti ve abatement strategies.