Characterization of the Global Sources of Atmospheric Ammonia from Agricultural Soils and its Deposition

Viney Aneja1, William Schlesinger2, Qi LI3, Alberth Nahas4 and William Battye5

Global ammonia (NH3) emissions into the atmosphere are projected to increase in the coming years with the increased use of synthetic nitrogen fertilizers and cultivation of nitrogen-fixing crops. Here, a statistical model (NH3_STAT) is developed for characterizing atmospheric NH3 emissions from agricultural soil sources, and compared to the performance of other global and regional NH3 models (e.g., EDGAR, MASAGE, MIX and U.S. EPA). The statistical model was developed by expressing a multiple linear regression equation between NH3 emission and the physicochemical variables. The model was evaluated for 2012 NH3 emissions. The results indicate that, in comparison to other data sets, the model provides a lower global NH3 estimate by 57%, (NH3_STAT: 14.2 Tg N yr-1; EDGAR: 33.0 Tg N yr-1). We also performed a region-based analysis (U.S., India, and China) using the NH3_STAT model. For the U.S., our model produces an estimate that is 143% higher in comparison to EPA. Meanwhile, the NH3_STAT model estimate for India shows NH3 emissions between -141% and -77% when compared to other data sets. A lower estimate is also seen for China, where the model estimates NH3 emissions 36-482% lower than other data sets. The difference in the global estimates is attributed to the lower estimates in major agricultural countries like China and India. The statistical model captures the spatial distribution of global NH3 emissions by utilizing a more simplified approach than those used by other readily available data sets. Moreover, the NH3_STAT model provides an opportunity to predict future NH3 emissions in a changing world. We also determine how much ammonia/nitrogen is being deposited globally.

 

1North Carolina State University, vpaneja@ncsu.edu
2Duke University, schlesingerw@caryinstitute.org
3North Carolina State University, qli17@ncsu.edu
4North Carolina State University, acnahas@ncsu.edu
5North Carolina State University, whbattye@ncsu.edu