Drivers for spatial, temporal and long-term trends in atmospheric ammonia and ammonium in the UK 1 1 1 1 1 1 Yuk S. Tang , Christine F. Braban , Ulrike Dragosits , Anthony J. Dore , Ivan Simmons , Netty van Dijk , Janet Poskitt2, Gloria Dos Santos Pereira2, Patrick O. Keenan2, Christopher Conolly3, Keith Vincent3, 5 Rognvald I. Smith1, Mathew R. Heal4 & Mark A. Sutton1 1CEH, Bush Estate, Penicuik, Midlothian EH26 0QB 2CEH, Lancaster Environment Centre, Bailrigg, Lancaster LA1 4AP 3Ricardo Energy & Environment, Gemini Building, Fermi Avenue, Harwell, Oxon OX11 0QR 10 4School of Chemistry, University of Edinburgh, David Brewster Road, Edinburgh EH9 3FJ Correspondence to: Y. Sim Tang (
[email protected]) Abstract. A unique long-term dataset from the UK National Ammonia Monitoring Network (NAMN) is used here to assess + spatial, seasonal and long-term variability in atmospheric ammonia (NH3: 1998-2014) and particulate ammonium (NH4 : 1999- 15 2014) across the UK. Extensive spatial heterogeneity in NH3 concentrations is observed, with lowest annual mean -3 -3 + concentrations at remote sites (< 0.2 µg m ) and highest in the areas with intensive agriculture (up to 22 µg m ), while NH4 -3 concentrations show less spatial variability (e.g. range of 0.14 to 1.8 g m annual mean in 2005). Temporally, NH3 concentrations are influenced by environmental conditions and local emission sources. In particular, peak NH3 concentrations -1 -1 are observed in summer at background sites (defined by 5 km grid average NH3 emissions <1 kg N ha y ) and in areas 20 dominated by sheep farming, driven by increased volatilization of NH3 in warmer summer temperatures.