Characterization of Atmospheric Ammonia Emissions from a Commercial Chicken House on the Delmarva Peninsula RONALD L. SIEFERT,* ,† JOSEPH R. SCUDLARK, ‡ AMELIA G. POTTER, § KIRSTEN A. SIMONSEN, † AND KAREN B. SAVIDGE ‡ Chesapeake Biological Laboratory, University of Maryland Center for Environm ental Science, 1 William s Street, Solom ons, Maryland 20688, Graduate College of Marine Studies, University of Delaware, Lewes, Delaware 19958, and Department of Natural Sciences, University of Maryland Eastern Shore, Princess Anne, Maryland 21853 A three-dimensional sampling grid using passive collectors was used to characterize the downwind gas-phase ammonia plumes originating from a commercial chicken house on the Delmarva Peninsula in the Chesapeake Bay watershed. Inverse Gaussian plume modeling was used to determine the source strength of the chicken house and the corresponding chicken emission factors. A total of seven field deployments were performed during two different flocks with a sampling duration ranging from 6 to 12.6 h. The deployments occurred during weeks 3, 4, and 5 of the 6-week chicken grow-out period in the months of May- July 2002. The ammonia emission factors ranged from 0.27 to 2.17 g of NH 3 -N bird -1 day -1 with a mean of 1.18 g of NH 3 -N bird -1 day -1 . Weighted emissions factors that accounted for the nonlinear increase in ammonia emissions over the 6-week grow-out period were also calculated and ranged from 0.14 to 1.65 g of NH 3 -N bird -1 day -1 with a mean of 0.74 g of NH 3 -N bird -1 day -1 . These weighted emission values would correspond to an annual release of approximately 18 × 10 6 kg of NH 3 -N to the atmosphere from broiler production on the Delmarva Peninsula. This assumes that the emission factors in this study are representative for the entire year with varying meteorological conditions and are representative of all chicken husbandry practices. The Delmarva Peninsula could represent a significant source of nutrient nitrogen to the Chesapeake Bay and Delaware Bay watersheds through atmospheric deposition when considering the size of this annual release rate, the relative short atmospheric lifetime of ammonia due to deposition,and the proximity of the Delmarva Peninsula to the Chesapeake and Delaware Bays. Introduction Atmospheric deposition of nitrogen (N) species (ammonia and nitrate) is estimated to contribute 27% of the total nutrient N load to the Chesapeake Bay (1). Both wet and dry deposition contribute to this atmospheric deposition of nitrogen species. Castro and Driscoll (1) used the best available wet and dry deposition data from the National Atmospheric Deposition Program (NADP), the Clean Air Statusand TrendsNetwork(CASTNET),and the Atmospheric Integrated Monitoring Network (AIRMoN). However within these data sets,drydeposition data forparticulate ammonium is scarce, and dry deposition data for gas-phase ammonia does not exist since gas-phase ammonia is not measured. Ammonia is a multi-phasic atmospheric species that can occur in the gas phase (NH3),in the particulate phase (NH4 + ), and in the aqueous phase (predominantly as NH4 + ). NHx is defined as the sum of ammonia (NH3) and ammonium (NH4 + ).There are large differencesbetween the drydeposition ratesofgas-phase NH3 and particulate-phase NH4 + (2).These differences can lead to high deposition rates of gas-phase NH3 near sources of gas-phase NH3 (2). The conversion of gas-phase ammonia to particulate-phase NH 4 + isdependent on the ambient concentrations of gas-phase and aerosol species(e.g.,acids)and can impact the transport ofammonia. Because of this multi-phasic chemistry, NH x has a relatively short atmospheric lifetime (hours to days) that is shorter than the atmospheric lifetime ofnitrate or sulfate (3).Studies in Western Europe have shown that the transport and deposition is a complex process near agricultural sources (4, 5). Current estimates of NH x sources and deposition in the Chesapeake Bay airshed are not well constrained. Arecent inventory for the Chesapeake Bay watershed indicates that agricultural livestock contribute 81% of the annual NH x atmosphericburden (6).However,such estimates are derived from animal-specific emission factors (7), which are often based on many assumptions. Values for emission factors varywidelydependingon thespecificanimalhusbandryand manure dispersal practices utilized. Annual broiler production on the Delmarva Peninsula, currently at 6 × 10 8 birds yr -1 , has increased more than 20- fold over the past two decades and has been cited for the 60% increase in NH4 + wet deposition observed nearby at Lewes, DE, during this time period (8). A primary concern when raising chickens in a confined space is the removal of elevated NH 3 inside the house by ventilation since NH3 has adverse health effects on the chickens. Other functions of a ventilation system include the removal of heat, the removal of moisture (this may also decrease NH 3 volatilization by keeping the litter dry), and the provision of oxygen. Side- wall ventilation and tunnel ventilation are two common methodsofventilation.Direct NH3 emissionsfrom ventilating chicken houses contribute to NHx emissions in the Chesa- peake Bay airshed. Previous studies have used different methods for mea- suringNH 3 emissions from agriculturalbuildings.Demmers et al. (9) used carbon monoxide as a tracer to determine the airflow rate through naturally ventilated livestock building while measuring NH3 concentrations to determine the NH3- emission factors for the livestock. Fowler et al. (5) measured NH3 concentrations near a broiler house surrounded by woodlands and calculated that only3.2%ofthe NH3 emitted from the poultry unit was deposited within 230 m of the house and that 10%was deposited within 1000 m.Asman (4) predicted somewhat greater deposition over comparable distances, which is influenced by factors such as source height,wind speed,atmospheric stability,surface resistance, surface roughness, and plant NH 3 compensation point. *Corresponding author e-mail: siefert@cbl.umces.edu; phone: (410)326-7386; fax: (410)326-7341. † University of Maryland Center for Environmental Science. ‡ University of Delaware. § University of Maryland Eastern Shore. Environ. Sci. Technol. 2004, 38, 2769-2778 10.1021/es0345874 CCC: $27.50  2004 American Chemical Society VOL. 38, NO. 10, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 2769 Published on Web 04/16/2004