Measurement of ammonia fluxes at a cattle feedlot using micrometeorological and spectroscopic techniques

The majority of the reactive nitrogen (N) inputs to the atmosphere are estimated to come from agricultural sources. Confined animal feeding operations (CAFO) in particular contribute a large portion of agricultural ammonia (NH3) emissions. At elevated levels, NH3 becomes an odor concern and contributes to regional air quality problems by serving as a precursor to fine particulate matter. NH3 measurements were conducted at a CAFO (30,000 head) in order to quantify NH3 emissions. Measurements were conducted using two approaches. Relaxed eddy accumulation (REA) techniques were employed to measure NH3 micrometeorologically, and coincidently NH3 emissions were determined using differential optical absorption spectroscopy (DOAS) combined with inverse dispersion modeling. Preliminary REA results show daytime ammonia fluxes ranging from 50 - 310 ėg m-2 s-1 over three days in April 2009.