Estimating ammonia fluxes from livestock operations using a network of conditionally-deployed diffusive samplers and inverse modeling

Diffusive/passive samplers can be used to measure spatial variations in ammonia and other trace gases near livestock operations, but results are often confounded by changing weather conditions during extended deployment periods (e.g., 2 weeks). A new type of conditional sampler was developed that only exposes the passive samplers when a user-defined set of wind and weather conditions are met. Samplers were deployed on portable tripods that were linked using a wireless sensor network. A base-station with an anemometer, wind vane, thermometer, and humidity sensor controlled all the tripods allowing synoptic sampling. Multiple tripods, equipped with Radiello diffusive NH3 samplers, were deployed at a dairy and programmed to only expose the passive samplers when the upwind source area represented a specific zone of the operation. Time-averaged ammonia concentrations were used to approximate emissions using both 2-D and 3-D inverse dispersion models. This approach provides a relatively low-cost technique for measuring the spatial variation in emissions near livestock operations and other strong ammonia sources.