||During recent years, it has become clear that ammonia is an important gas in relation
to different environmental issues, such as acidification, eutrophication, human health
and climate change (through particle formation). Therefore, there is a growing need
to develop and apply instrumentation suitable for research into emission, dispersion,
conversion and deposition of ammonia and ammonium. Recently, several instruments were
developed suitable for measuring concentrations in ambient conditions even at very
low levels, such as ammonia sensors suitable for monitoring and research, deposition
measuring systems and aerosol samplers for on-line measurement of aerosol composition.
These instruments have been tested and applied in a number of field studies. These
studies include dry deposition measurements, ammonium nitrate studies in relation
to the (in)direct aerosol effect, emission studies and policy evaluation with concentration
and deposition monitoring data. The policy evaluation study showed that the measures
to reduce ammonia emissions were not as successful as projected beforehand by statistical
studies. (C) 2001 Elsevier Science Ltd. All rights reserved.