A Review of Methods for measuring Emission Rates of Ammonia from Livestock Buildings and Slurry or Manure Stores, Part 2: monitoring Flux Rates, Concentrations and Airflow Rates

Given the important role of ammonia emissions in atmospheric chemistry and subsequent damage to the environment, and given that livestock production is the major source of these emissions, there is a strong need for good methods to measure ammonia emission rates from livestock buildings and slurry or manure stores e.g. to guide abatement strategies. In this paper, techniques needed when monitoring these emission rates have been reviewed. The review thus amplifies and extends a consideration of the basic approaches to the above measuring task, presented in a companion review paper. A wide range of techniques was identified for measuring low concentrations of ammonia in air, for measuring airflow rates and for directly measuring ammonia flux rates. The `ammonia measurement by annular denuder sampling with on-line analysisʹ (AMANDA) rotary annular denuder is recommended as the best technique overall for measuring ammonia concentrations. Wet chemistry offers a less sophisticated but generally acceptable alternative: acid bubblers or simple active denuders can measure ammonia concentrations reliably, while `Ferm tubeʹ passive samplers offer the potential for measuring ammonia fluxes directly, thus eliminating the need for any measurement of airflows. Acid bubblers and Ferm tubes are both cheaper than the AMANDA, but, unlike the AMANDA, cannot measure continuously. If an approach to determining the emission rate from a building is chosen which necessitates the measurement of ventilation rate, then the use of fan-wheel anemometers should be considered where the building is force-ventilated. If, however, the building is naturally ventilated, a tracer gas method is necessary. Sulphur hexafluoride is the recommended tracer, not only for this latter scenario, but also for use with the tracer ratio method for determining source strengths directly.