Brief Summary of Minutes of Annual Meeting

Please see Summary of Meeting Minutes attached as a PDF file. Thank you.

NC1213: Sources and fate of ammonia across the landscape

The main objectives of this project are to:

1: Better understand and quantify ammonia emissions from crop and livestock across spatial scales.

2: Characterize the magnitude and variability of ammonia deposition in natural and agricultural landscapes.

3: Understand the transport and fate of NH3 emissions and its impact on PM formation and reactive nitrogen deposition.

Research Activities and Short-term Outcomes

Our project team has made significant progress towards meeting the three main objectives outlined above. For example, at the University of Minnesota, Griffis and colleagues have been measuring ammonia from a tall tower (200 m) trace gas observatory to quantify the seasonal and inter-annual variability of regional ammonia emissions and have used these data within an inverse modeling framework to estimate regional emissions and identify important hotspots and areas of significant deposition. The Griffis group have also conducted aircraft ammonia measurements across the region to characterize emissions from croplands, large animal feedlots, and natural vegetation. These data and analyses generally reveal that ammonia emissions have been underestimated by previous bottom-up emission inventories.

Aircraft observations and satellite ammonia emission estimates are also being pursued by multiple members of our research team including April Leytem, Tim Griffis, and Alex Frie. These data and analyses provide exciting opportunities to improve our understanding of emission/deposition behavior and will provide much needed data for validating state-of-the-art bottom-up emission factors and activity data.

Our team is also examining how downwind deposition of reactive nitrogen is impacting our National Parks. For example, Bret Schichtel and collaborators have been modeling the transport of and fate of ammonia emissions on PM formation and reactive nitrogen deposition using the Comprehensive Air Quality Model with Extensions (CAMx) to simulate the contributions of agriculture and other sources to wilderness areas. Such modeling activities are critical toward understanding how downwind transport and deposition are affecting nitrogen pollution in our "pristine" natural wilderness areas and for planning efforts related to air quality management.

Colleagues from the EPA (John Walker, Melissa Puchalski, Greg Beachley) have made substantial advances in developing, improving, and testing technologies for quantifying ammonia fluxes and modeling ammonia fluxes using  a much needed bi-directional approach.  For example, EPA is continuing to develop a bi-directional flux model that can be applied at existing AMoN sites. This project began in 2017 by conducting seasonal field measurements at three AMoN sites to develop a database of soil and vegetation chemistry, micrometeorology, and canopy characteristics. These databases are used to parameterize input to the bi-directional flux model. Using the STAGE framework, ammonia fluxes will be derived from site specific AMoN concentrations and surface parameterizations (compensation points) to provide the best model estimates of NH₃ deposition. This tool will support Objective 2 by providing seasonal and annual bi-directional flux estimates for the 27 sites in the North Central region of the US.

Further, two Conditional Time-Integrated Average Gradient (COTAG) flux measurement systems have been deployed in the Magic Valley region of Idaho. Measurements from the COTAG will be used to quantify dry deposition of NH₃, HNO₃, NH₄, and NO₃ on a bi-weekly time-scale (Famulari et al., 2010; Tang et al., 2009). An open-path quantum cascade laser-based NH₃ sensor has recently been deployed in the Magic Valley to provide highly time resolved NH₃ dry deposition and constrain the time-integrated flux measurements from the COTAG (Pan et al. 2021). This effort is supported by EPA, USDA, and Princeton University. The results will be used to model seasonal and annual estimates of dry deposition to improve total deposition budgets and for evaluation of dry deposition estimates from field-scale models and chemical transport models. The measurements will help to improve the air-surface exchange algorithms and biogeochemistry parameterizations within CTMs. Plans to expand this effort to the North Central region have been paused due to EPA staffing and funding shortages.

Integration of Research Activities and Key Milestones

Based on the above research activities and accomplishments, our project team has recognized that we are in an unique position to re-examine bottom-up ammonia emission factors and activity data used to estimate emissions for the United States. Going forward, we will continue to address the three main objectives outline above in NC1213. However, an emerging theme that will bring our group together for closer collaboration is the pursuit of validating bottom-up ammonia emissions based on 1) state of the art flux measurements at the field scale; 2) tall tower and aircraft measurements at the regional scale; and 3) satellite observations that provide unprecedented spatial coverage. We will be contacting US EPA for a state-of-the art update regarding their process of developing emission inventories and how best to move forward with evaluating the emission factors vs the activity data that are used to drive those simple models.

Recent Publications and Presentations

Beltran, I., van der Weerden, T.J., Alfaro, M.A., Amon, B., de Klein, C.A.M., Grace, P., Hafner, S., Hassouna, M. Hutchings, N., Krol, D.J., Leytem, A.B., Noble, A., Salazar, F., Thorman, R.E., and Velthof, G.L. DataMan: A global database of nitrous oxide and ammonia emission factors for excreta deposited by livestock and land-applied manure. J. Environ. Qual. 2021. http://dx.doi.org/10.1002/jeq2.20186

Cuchiara, G. C., Hand, J. L., Barna, M. G., and Schichtel, B. A. (2021), Assessing the impact of agricultural NH3 emissions on the excess nitrogen deposition in U.S. national parks, presented at Air & Waste Management Association Specialty Conference - Atmospheric Optics: Aerosols, Visibility, and the Radiative Balance, paper #AV #119, Bryce Canyon, Utah, October 5-8.

Frie, A., Griffis T.J. et al., (2022) Atmospheric ammonia fluxes in the USA Corn Belt: Insights from aircraft measurements and WRF-CHEM modeling of a spring peak emission period,  American Geophysical Union (AGU), Chicago, Illinois, USA.  

Leytem, A.B., P. Williams, S. Zuidema, A. Martinez, Y.L. Chong, A. Vincent, A. Vincent, D. Cronan, A. Kliskey, J.D. Wulfhorst, L. Alessa, and D. Bjorneberg. Cycling phosphorus and nitrogen through cropping systems in an intensive dairy production region. Agronomy. 2021. 11,1005 https://doi.org/10.3390/agronomy11051005

Rotz, C.A., R.  Stout, A.B. Leytem, G. Feyereisen, H. Waldrip, G. Thoma, M. Holly, D. Bjorneberg, J. Baker, P. Vadas and P. Kleinman. Environmental assessment of United States dairy farms. J. Cleaner Prod. 2021. 315:128153 https://doi.org/10.1016/j.jclepro.2021.128153

Schichtel, B. A., Cuchiara, G. C., Hand, J. L., Barna, M. G., and Vimont, J. (2022), Assessing the impact of agricultural activities on air quality in national parks and other rural lands, presented at National Acid Deposition Program Annual Conference, Knoxville, TN, November 14-18.

VanDerWeerden, T.J., Noble, A., De Klein, C.A.M., Hutchings, N., Thorman, R.E., Alfaro, M.A., Amon, B., Beltran, I., Grace, P., Hassouna, M., Krol, D.J., Leytem, A.B., Salazar, F., and Velthof, G.L. Ammonia and nitrous oxide emission factors for excreta deposited by livestock and land-applied manure. 2021. J. Environ. Qual. DOI: 10.1002/jeq2.20259

Walker, J.T., Chen, X., Wu, Z., Schwede, D., Daly, R., Djurkovic, A., Oishi, A.C., Edgerton, E. Bash, J., Knoepp, J., Puchalski, M., Miniat, C.F. (2022) Atmospheric Deposition of Reactive Nitrogen to Deciduous Forest in the Southern Appalachian Mountains. Biogeosciences [preprint] (https://doi.org/10.5194/bg-2022-133)

Xuehui Guo, Da Pan, Ryan W. Daly, Xi Chen, John T. Walker, Lei Tao, James McSpiritt, Mark A. Zondlo, 2022. Spatial heterogeneity of ammonia fluxes in a deciduous forest and adjacent grassland. Agricultural and Forest Meteorology, 326, 109128.