@article{arogo_westerman_liang_2003, title={Comparing ammonium ion dissociation constant in swine anaerobic lagoon liquid and deionized water}, volume={46}, DOI={10.13031/2013.15441}, abstractNote={The dissociation constant of ammonium ion both in deionized water and swine anaerobic lagoon liquid was 
determined experimentally in a convective emission chamber at three temperatures (15.C, 25.C, and 35.C) commonly 
experienced in lagoons in the south and southeastern regions of the U.S. Ammonium chloride (NH4Cl) salt was used to make 
the solution for the deionized water tests. The dissociation constant (Kd) values obtained for NH4Cl in deionized water 
approximately doubled with every 10.C increase in liquid temperature from 15.C to 35.C. A similar trend was obtained for 
lagoon liquid in the 25.C to 35.C liquid temperature range, but the Kd values for the lagoon liquid were ~50% of those for 
NH4Cl in deionized water. However, at 15.C, the Kd value for the lagoon liquid was almost the same as for deionized water, 
and was 0.75 the lagoon liquid value at 25.C. Based on these results, it can be concluded that the Kd values of ammonium 
ion in anaerobic lagoon liquid was 50% of the value in deionized water at 25.C and 35.C, and 94% of the value at 15.C. 
This implies that for lagoons with characteristics similar to those of the anaerobic lagoon liquid reported in this study, the 
Kd values (normally derived from NH4 
+ dissociation in deionized water) used in ammonia volatilization calculations should 
be adjusted to a fraction of that in deionized water. More studies to determine the Kd values for lagoon liquids with different 
total ammonia nitrogen concentrations and solid contents are needed. Studies should include the effects of temperature and 
perhaps distinguish between the effects of dissolved and suspended solids on the dissociation constant.}, number={5}, journal={Transactions of the ASAE}, author={Arogo, J. and Westerman, P. W. and Liang, Z. S.}, year={2003}, pages={1415–1419} }
 @article{liang_westerman_arogo_2002, title={Modeling ammonia emission from swine anaerobic lagoons}, volume={45}, DOI={10.13031/2013.8859}, abstractNote={A mathematical model to estimate ammonia emission from anaerobic swine lagoons was developed based on the 
classical two–film theory. Inputs to the model are wind speed and lagoon liquid properties such as total ammonia nitrogen 
(TAN) concentration, pH, and temperature. Predicted emission rates of ammonia increase when any of these parameters are 
increased, but the relationship is linear only with TAN concentration. The dissociation constant (Kd) for ammonia in lagoon 
liquid is also an important factor, with higher flux predictions for higher Kd. The model was validated by comparing the model 
outputs to measured fluxes from two lagoons in North Carolina. The predicted ammonia emission fluxes for the two lagoons 
ranged from 1 to 38 kg NH3–N/ha–d, which was a wider range than the fluxes measured (2.5 to 22 kg N/ha–d) by other 
researchers using the micrometeorological method. 
Compared to measured fluxes at each lagoon, the model tended to predict higher ammonia fluxes at lagoon A and lower 
fluxes at lagoon B when a Kd of 0.5 was used. Additional information is needed regarding ammonia dissociation (Kd) values 
for anaerobic lagoon liquid. Comparison of the model results with a linear regression equation indicated that the model 
predicted much higher fluxes at temperatures above 25 
³ 
C and at upper ranges of pH and wind speed. Finally, the model was 
used with typical lagoon TAN concentration and pH, and average monthly values for wind speed and estimated liquid 
temperature at Raleigh, North Carolina, to predict monthly ammonia emissions for a typical anaerobic swine lagoon in North 
Carolina. The highest and lowest monthly ammonia emission occurred in June and January, respectively. Based on the 
average monthly emissions, it is estimated that the average annual ammonia nitrogen emission rate from the surface of a 
typical lagoon in North Carolina would be 234 g/m 2 or 2340 kg/ha. However, the model and results from other researchers 
indicate that ammonia emission can vary greatly.}, number={3}, journal={Transactions of the ASAE}, author={Liang, Z. S. and Westerman, P. W. and Arogo, J.}, year={2002}, pages={787–798} }