Comparison of Ambient Ammonia Measurement Techniques from Dairy Area Sources

Previous studies of ag-related NH3 concentrations and/or emissions have used a variety of techniques, with very few studies offering adequate instrumental comparisons. In the fall of 2007, NH3 concentrations/emissions were monitored for a one week period at a waste treatment lagoon on a 6000-cow dairy in Idaho using five separate methodologies. Up to twenty-five Ogawa passive samplers were dispersed around the perimeter of the lagoon, with a concentrated bank of samplers arrayed along the predicted downwind side of the facility. A URG acid/base gas denuder system, assembles with three series denuders configured for NH3 collection, was collocated at a single sampling site with one of the passive samplers. The collected samples from the passive samplers and the denuder tubes were quantified via ion chromatography at Utah State University. Two separated UV-Sentry open-path ultra violet differential optical absorption spectrometers (UV-DOAS) were used to measure the integrated NH3 concentrations along an approximately 200 m pathlength on both the up and downwind sides of the lagoon. Two infrared Fourier Transform Spectrometers (FTS) were also used to quantify ambient NH3 along the same downwind pathlength. Finally, a small, floating wind tunnel system, coupled with a Thermo Fisher Model 17C chemiluminescence NH3 monitor, was used to measure direct NH3 emissions from the surface of the lagoon. In 2008, NH3 measurements were made at a 950-milking cow dairy in central California. Two FTS systems were employed upwind and downwind of the whole facility, while numerous passive samplers were place throughout the dairy. Quantification of all ambient concentrations have been completed and the measurements will be used in conjunction with inverse modeling techniques (both LaGrangian and Eularian) to estimate lagoon and dairy-wide NH3 emissions