Submitted to: Western Dairy Management Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2006
Publication Date: 3/1/2006
Citation: Marcillac, N.M., Hanan, N.P., Lee, T., Follett, R.F., Stanton, T.L., Johnson, D.E. Air emissions from dairy CAFO's: multi-scale measurements and process based modeling. Western Dairy Management Conference.
Interpretive Summary: Seasonal variation was seen for all compounds, with highest concentrations in the summer for NH3, CO2, CH4, and N2O, and in the winter for HNO3 and NH4. The increase in HNO3 and NH4 in the winter illustrates the preference of the reaction of HNO3 and NH3 to form ammonium salts (NH4NO3), as does the higher upwind concentration of HNO3 and increase in downwind NH4. Some diurnal variation has been observed, but more data is needed to verify any trends. The goal of the project is to develop and test process based estimations of CAFO air emissions. First, the species, climatic, and spatial data will be integrated into a model that will attempt to show the behavior of the emission plume. Additionally, a model will be created to characterize ammonia emissions by estimating ammonia fluxes from specific farm components and validating those values with data collected by the system. The multi-scale measurements and modeling associated with this project will investigate emissions outputs along with diurnal and seasonal variability.
Technical Abstract: This study is aimed at quantifying emissions of ammonia (NH3), ammonium (NH4), nitric acid (HNO3), PM2.5, methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) from multi-component dairy systems, and examine their spatial, diurnal, and seasonal variability. Using a unique mobile sampling methodology employing large helium blimps and a variety of air and climatic sampling equipment, trace gases and particulates were measured at five heights at three locations downwind, and three heights at one location upwind of two dairies. Heights were chosen based on Gaussian distribution modeling and usually spread from 2 to 40 m. Volatile gases (NH3 and HNO3) and particulates (NH4 and PM2.5) were collected using filter packs specially designed for this system attached at each height, with less reactive gases (CH4, CO2, and N2O) pumped to the ground and collected using syringe pumps. In addition, detailed climatic data (wind speed, wind direction, temperature, relative humidity, and pressure) were measured at the five sample heights using a DigiCORA Tethersonde System (Vaisala, Boulder, CO). Average wind speeds, taken at each height along with mean gas and particulate concentrations, can be used to estimate mean horizontal flux at each sample location and be integrated with respect to location to estimate mass flow within the plume. This innovative mass balance measurement technique was designed to overcome the limitations of other sampling systems and provide a spatially resolved characterization of the emission plume.