Title:
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An automated method of ammonia flux measurement for agriculture
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Ammonia emissions arising from intensive methods in agriculture are now recognized
as having a considerable impact upon the wider environment. In addition to
environmental pollution risks, concerns have been raised over livestock housing
conditions with regard to the impact upon the health of employees and animal
welfare. The goal was to develop a means of measuring ammonia flux emissions at
the periphery of naturally ventilated livestock buildings in near real-time, as the basis
for an automated system. Conducting polymer gas-sensors were determined to be the
best approach to the problems of low-cost multi-point sampling in a relatively harsh
environment. Sampling frequencies dictated an indirect measurement approach,
requiring knowledge of wind velocity and ammonia concentration. Initial evaluation
of polypyrrole-based sensor arrays located upon AromaScan™ A32S ceramic
substrates, in conjunction with a commercially available Honeywell™ AWM3300
airflow sensor, indicated that ammonia concentration could be correlated to the pre-equilibrium
rising response curves of a number of sensors. Simulation of a ventilation
opening subjected to the vagaries of the UK weather, was undertaken at SRI and this
work demonstrated that the gas-sensing arrays were integrating ammonia flux over
time. Results for the new method of flux determination were compared with the "gold
standard" values calculated from mass-loss values over time for the liquefied gas.
Without the benefit of temperature and humidity compensation, there was a good
correlation between the two methods although it became apparent that an exposure
history compensation algorithm would be needed to adjust for extreme transitions in
ammonia flux values.
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