Measurement and modeling of atmospheric flux of ammonia from dairy milking cow housing: Fid-Bau Portal

Measurement and modeling of atmospheric flux of ammonia from dairy milking cow housing

Rumburg, Brian / Mount, George H. / Filipy, Jenny / Lamb, Brian / Westberg, Hal / Yonge, David / Kincaid, Ron / Johnson, Kristen

Abstract

AbstractAtmospheric ammonia $({NH}_{3})$ measurements are needed to better understand the impacts of ${NH}_{3}$ emissions on aerosol formation and concentrations and anthropogenic changes to the N cycle. This paper describes concentration measurements of ${NH}_{3}$ using differential optical absorption spectroscopy (DOAS), tracer ratio flux experiments, and development of a ${NH}_{3}$ emissions model from a dairy milking cow free stall house with concrete floors. An area source tracer gas ratio method was used to determine ${NH}_{3}$ fluxes which involved releasing ${SF}_{6}$ as the tracer gas from the upwind edge of the stalls and measuring the tracer concentration downwind along with the DOAS ${NH}_{3}$ measurements. The flux is calculated from the ratio of the ${NH}_{3}$ and ${SF}_{6}$ concentrations and the ${SF}_{6}$ release rate and taking into account the differences in area and dispersion. The measured stall flux for the summers averaged $29 \pm 19 g {NH}_{3} {cow}^{- 1} h^{- 1}$ at an average temperature of $18 \pm 5^{\circ} C$ . The emissions model calculated liquid ${NH}_{3}$ concentrations in urine puddles, ${NH}_{3}$ volatilization, theoretical and empirical mass transfer to the bulk atmosphere, and ${NH}_{3}$ transport. The predicted concentrations were within $\pm 30 %$ using an empirical mass transfer coefficient and within $\pm 41 %$ using a theoretical mass transfer coefficient. Total annual ${NH}_{3}$ emissions for the dairy of 185 milking cows was 7400kg or $40 kg {NH}_{3} {cow}^{- 1} {year}^{- 1}$ , estimated total N excretions are $180 kg {cow}^{- 1} {year}^{- 1}$ . This agrees with a N mass balance of the dairy. The model was very sensitive to urine puddle pH and also showed that emissions are temperature dependent.