Weather-Based Conditional Sampling of Ammonia Using Robotic Diffusive Samplers.

Diffusive/passive samplers can be used to measure the 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., 1 to 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.  The samplers were housed in air-tight tubes that could be opened and closed with a motorized actuator controlled by a datalogger.  Samplers were deployed on portable tripods equipped with an anemometer, wind vane, thermometer, and humidity sensor.  Multiple tripods, equipped with Radiello diffusive NH₃ samplers, were positioned near cattle feedlots and dairies and programmed to only expose the passive samplers when the upwind source area represented a specific zone of the operation. This new methodology allows improved detection of high emissions zones or transport pathways near livestock operations and provides more accurate measurements of downwind gradients.