ASSESSMENT OF THE MAGNITUDE OF AMMONIA EMISSIONS IN THE UNITED-KINGDOM

Estimates of ammonia emission in the U.K. have been critically reviewed with the aim of establishing the magnitude and uncertainty of each of the sources. European studies are also reviewed, with the U.K. providing a useful case study to highlight the uncertainties common to all ammonia emission inventories. This analysis of the emission factors and their application to U.K. sources supports an emission of 450 (231-715) Gg NH3 yr(-1). Agricultural activities are confirmed as the major source, providing 406 (215-630) Gg NH3 yr(-1) (90% of the total), and therefore dominate uncertainties. Non-agricultural sources include sewage, pets, horses, humans, combustion and wild animals, though these contribute only 44(16-85) Gg yr(-1). Cattle represent the largest single uncertainty, accounting for 245 (119-389) Gg yr(-1). The major uncertainties for cattle derive from estimation of the amount of nitrogen (N) excreted, the % N volatilized from land spreading of wastes, and the % N volatilized from stored farm-yard manure. Similar relative uncertainties apply to each of sheep, pigs and poultry, as well as fertilized crops, though these are quantitatively less important. Accounting for regional differences in livestock demography, emission of 347, 63 and 40 Gg yr(-1) are estimated for England & Wales, Scotland, and Northern Ireland, respectively. Though very uncertain, the total is in good agreement with estimates required to balance the U.K. atmospheric NHx budget.