Differential optical absorption spectroscopy (DOAS) measurements of atmospheric ammonia in the mid-ultraviolet from a dairy: Concentrations, emissions, and modeling

Atmospheric ammonia (NH3) effects on the atmosphere, environment, and human health is not well understood due to a lack of information about ammonia's emissions, transport, and fate. Ammonia in the atmosphere reacts to form particulate matter below 2.5 microns in aerodynamic diameter (PM2.5) which is regulated by the Environmental Protection Agency (EPA). The largest anthropogenic source of atmospheric NH3 is animal excreta and dairy cows are the largest per animal emission source.; The objectives of this work were to measure and model NH3 emissions from the Washington State University (WSU) dairy. Short-path differential optical absorption spectroscopy (DOAS) was used to measure NH3, and an area source tracer ratio technique was used to measure emission fluxes. Measurements were made from the housing area, waste lagoons, and fields undergoing sprinkler application. Emissions models were developed to understand the physical processes and transport of NH3. Housing emission fluxes for the summer averaged 8.1 +/- 5.2 mg cow-1 s-1 at 18° C average temperature. The housing model had an error of +/-30% when compared to measured concentrations. Lagoon emission fluxes ranged from 30 mug m-2 s-1 at an air temperature of 11°C to 150 mug m-2 s-1 at an air temperature of 27°C. The lagoon model had an error of +/-21%. An aeration experiment was conducted with commercial aerators and no changes in liquid or downwind NH3 concentrations were detected during aeration. Slurry application emissions from the sprinkler were 18% of the slurry ammonia-N concentration. The initial tracer flux from the field was 47 mug m-2 s -1 and this decreased to 17 mug m-2 s-1 during the experiment due to slurry infiltration into the soil.; A total dairy emission model was developed for use with air quality models using the WSU algorithms. The total annual emissions are estimated to be 130 kg NH3 cow-1 yr-1, with 40 kg from housing, 55 kg from waste lagoons, and 34 kg from waste application. Annual emissions are in excellent agreement with annual N mass balance of the dairy. This is significantly larger than the EPA estimates which are based upon European data.