Introduction

Abstract

Atmospheric ammonia is emerging increasingly as the key transboundary air pollutant that will contribute to future impacts of nitrogen and acidity on terrestrial ecosystems in Europe. At the same time, ammonia is making an increasing relative contribution to particulate matter, with its associated human health risks. These features are shown clearly in Fig. 1.1 below, from the Clean Air For Europe (CAFE) programme. Thus, by 2020, it is estimated that NH3 will be the largest single contributor to each of acidification, eutrophication and secondary particulate matter in Europe. This increase is particularly a reflection of the success of European policies to reduce SO 2 and NOx emissions. As a result, NH3 is increasingly dominating nitrogen and acidifying inputs, while reducing ammonia emissions and the associated environmental impacts remain major challenges for the future. © 2009 Springer Netherlands.