Advances in Support of the CMAQ Bidirectional Science Option for the Estimation of Ammonia Flux from Agricultural cropland Ellen Cooter U.S. EPA, National Exposure Research Lab, Research Triangle Park, NC Verel Benson Benson Consulting, Columbia, MO Limei Ran Institute for the Environment, University of North Carolina, Chapel Hill, NC 2013 CMAS Conference, Chapel Hill, NC October 29, 2013

2 Research Drivers Increases in land and water N inputs on regional to global scales over the last several decades pose a growing threat to human health and ecosystem sustainability. Policy actions that address this threat demand improved characterization of all aspects of the N-cycle, including air quality.

Areas in need of improved treatment include: Characterization of nitrogen species such as NH 3 that exhibit bi-directional air-surface exchange. More complete integration of agricultural practices and meteorologically-driven emissions to reduce NH 3 and inorganic PM 2.5 concentration and deposition uncertainty. Development of the capacity to explore options that support joint air, land and water environmental outcomes to protect human health and ecosystems.

Soil emissions can be important ~85% of ammonia emissions come from agriculture and ~ 75% of agricultural emissions come from livestock production. Livestock operations are primarily NH 3 emitters (unidirectional), with flux estimated as a function of livestock numbers and meteorology. Crop soil flux is often bidirectional (emissions and deposition) and is a complex function of farm management, weather and ambient atmospheric and soil ammonium concentrations. Sensitivity studies of bi-directional CMAQ suggest that soil emission potential (Γ s ), a function of fertilizer application rate, depth, atmospheric deposition and nitrification rate, is an important source of atmospheric N emission uncertainty (Dennis, et al., 2013).

Bidirectional CMAQ Implementation Cooter et al. (2012)

How do you get the initial soil ammonium, soil pH and the daily fertilizer application and depth to run BIDI?

Simulates C, N, P biogeochemistry for spatial scales ranging from a single field site to global gridded domains at a daily time step Addresses natural as well as intensively managed terrestrial systems Widely used and internationally vetted The Environmental Policy Integrated Climate (EPIC) model

How do you get the initial soil ammonium, soil pH and the daily fertilizer application and depth to run BIDI?

The FEST-C User Interface – facilitates user-generated CMAQ-ready fertilizer input for any gridded domain, grid cell resolution and weather year by creating and submitting executable scripts.

Open Scenario New Scenario Copy Scenario Save Scenario Delete Scenario Exit Scenario Scenario creation requires minimal inputs

BELD Data Generation creates a BELD landuse coverage matching the domain and grid resolution of the scenario via spatial allocator software.

User can select one, several or all crops Multiple weather year simulations require only the new weather data and this step be re-run.

FEST-C Input to CMAQ

How much fertilizer is surface applied and how much is incorporated? Grain Corn in Southern Plains 92.5% inorganic N – 60% anhydrous ammonia – 2.5% DAP – 30% Nitrate 7.5 % organic N (manure) Winter Wheat in Southern Plains 88% inorganic N – 40% anhydrous ammonia – 15% ammonium nitrate – 6% urea – 3.8% monoammonium phosphate – 2.9% liquid ammonia – 20% nitrate 12.3% organic (manure)

The system does a reasonable job reproducing regional patterns of reported agricultural fertilizer purchases and use EPIC Application Fertilizer Sales Gronberg and Spahr (2012)

Agricultural management information can be produced for various CMAQ domains to address questions of spatial scale

The importance of interannual variability for NH 3 emissions lies in met-driven application timing

FEST-C currently supports both NCC and UNC computer systems and will soon be tested on a stand-alone Linux workstation. There is a poster presented by Limei Ran and a terminal set up for folks to try out the interface during poster session 2 this evening. There is a web page on the CMAS site for FEST-C that includes download and installation instructions and system documentation.

For information about recent CMAQ ambient air and deposition performance improvements resulting from invocation of the bi-directional option, see Jesse Bash’s poster this evening in the Model Evaluation and Analysis section of poster session 2.

Questions? Ellen Cooter U.S. EPA, National Exposure Research Lab, Research Triangle Park, NC

The Environmental Policy Integrated Climate (EPIC) model

Future Fertilizer Scenario Improvements Creation of an “average” daily deposition gridded data layer to be used during spinup and to offer a more consistent “first guess” option for specific application years. Movement to a more recent module FORTRAN version of EPIC that improves estimation of N2O emissions and, perhaps, simulation times. Update of statistical weather files. Addition of tiling and rotation management options.