, Volume 1, Issue 5-6, pp 177-188

Measurement and Modelling of Ammonia Emissions at Waste Treatment Lagoon-Atmospheric Interface

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Abstract

Global emissions of ammonia are approximately 75 Tg N/yr (1 Tg =1012g). The major global source is excreta from domestic animals (∼ 32 Tg N -1yr-1). Waste storage and treatment lagoonsare used to treat the excreta of hogs in North Carolina (NC). Proteins and nitrogen rich compounds in the lagoon are convertedto ammonia, through a series of biological and chemical transformations. The process of ammonia emission has been investigated using two different model approaches: (1) CoupledMass Transfer with Chemical Reaction Model (Model I), and (2)Mass Transport without Chemical Reaction Model (Model II). Asensitivity analysis is performed with the models, and the modelresults are compared with ammonia emission experiments at a swinewaste storage and treatment lagoon in NC using a dynamic emissionflux chamber.Results of model predictions of emission flux indicate an exponential increase in ammonia flux with increasing lagoontemperature and pH, a linear increase with increasing lagoontotal ammoniacal nitrogen (TAN), and a secondary degree increasewith the increasing wind speed. In addition, the fluxes predictedby Model I are consistently larger than fluxes predicted by Model II. Experimental values of flux agreed well with model predictions, with the experimental values lying in different positions between the two model predictions under different physical and chemical conditions. Further, when compared to diurnal and seasonal experimental flux values, Model I corroborates the results in calm meteorological conditions (windspeed U10 = 1.5 m s-1). However, the observed results are better predicted by Model II during unstable conditions, when wind speeds are higher than 2.0 m s-1 and physical transfer process functions dominate.