| The uncertainties in emissions of ammonia (NH3) in Europe are large, partially due to the
difficulty in monitoring of ambient concentrations due to its sticky nature. In the
European Monitoring and Evaluation Program (EMEP) the current recommended
guidelines to measure NH3 are by coated annular denuders with offline analysis. This
method, however, is no longer used in most European countries and each one has
taken a different strategy to monitor atmospheric ammonia due to the increase of
commercial NH3 monitoring instrumentation available over the last 20 years. In June
2014, a 3 year project funded under the European Metrology Research Programme,
“Metrology for Ammonia in Ambient Air” (MetNH3), started with the aim to develop
metrological traceability for the measurement of NH3 in air from primary gas mixtures and
instrumental standards to field application. This study presents the results from the field
intercomparison (15 instruments) which was held in South East Scotland in August
2016 over an intensively managed grassland. The study compared active sampling
methods to a meteorological traceable method which was developed during the project
with the aim to produce a series of guidelines for ambient NH3 measurements.
Preliminary results highlight both the importance of inlets and management of relative
humidity in the measurement of ambient NH3 and of the requirement to carry out
frequent intercomparison of NH3 instrumentation. Overall, it would be recommended
from this study that a WMO-GAW world centre for NH3 would be established
and support integration of standards into both routine and research measurements. |