Estimating Ammonia Emissions from a Dairy Using Robotic Diffusive Samplers and Inverse Modeling

摘要

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., 2 weeks). Anew 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 NH_3 samplers, were deployed at a commercial dairy and programmed to only exposethe passive samplers when the upwind source area represented a specific zone of the operation and wind speeds were in excess of 1.4 m/s. During the summer months, ammonia concentrations consistently ranged between 600 to 1200 ppb; the highest concentrations were downwind of a large anaerobic lagoon. Time-averaged ammonia concentrations were used to approximate emissions using a 2-D inverse dispersion model. This methodology provides a relatively low-cost technique for measuring the spatial variation inemissions near livestock operations and other strong ammonia sources.