Characterizing ammonia emissions from swine waste treatment lagoons in eastern North Carolina

Ammonia emission fluxes from treatment storage waste lagoons were measured at two swine farms with conventional lagoon and spray technology in eastern North Carolina. Lagoon parameters, such as lagoon temperature, pH, and ammonia content of the lagoon waste water, as well as the relevant meteorological parameters, such as wind speed and direction, air temperature, and humidity, were also measured at the same time. Ammonia fluxes were measured at various locations on waste storage lagoons, using a floated flow-through dynamic chamber system interfaced with environmentally-controlled mobile laboratory. The early fall and winter field campaigns were conducted during September 9-October 11, 2002(lagoon temperatures ranged from 21 to 34C) and January 6-February 2, 2003(lagoon temperatures ranged from 1.7 to 12C), respectively. Significant differences in ammonia fluxes during the warm and cold seasons were observed at both the farms. Average ammonia fluxes during the warm season were approximately an order of magnitude larger than those during the cold season.

Typical diurnal variations of lagoon surface temperature and ammonia flux were observed during both the experimental periods. Also, an exponentially increasing flux with increasing lagoon surface temperature was observed. A simple linear regression relationship between the logarithm of ammonia flux and lagoon surface temperature was obtained, in good agreement with a similar relationship obtained earlier by some of the co-authors from measurements made at another farm(Farm 10) in eastern North Carolina. On closer examination of our new data, however, the difference, D, between the air temperature and the lagoon surface temperature was found to also influence the ammonia flux, especially when D > 0. This "hot air" effect is included in the multiple regression model obtained in this study. Some of the farm-related differences in the ammonia flux were eliminated or minimized in our statistical/observational model by considering the total emission from the lagoon, normalized by the total live animal weight at the farm.

Relationships between the lagoon ammonia flux/emission and relevant chemical parameters, such as pH and total kjeldahl nitrogen(TKN) were also examined. The lagoon pH stayed within a relatively narrow range from 7.7 to 8.5 during our fall and winter field campaigns, and no statistically significant correlation between ammonia flux and pH was found. Although, the TKN concentration was positively correlated with the lagoon ammonia flux, this correlation was confounded by significant seasonal variability of TKN concentration, with lower TKN values observed in fall with higher ammonia fluxes, and higher TKN concentrations observed in winter with lower ammonia fluxes.