Grantee Research Project Results
2000 Progress Report: An Object-Oriented Model for Nitrogenous Pollutants from Swine Waste Land Application
EPA Grant Number: R827955Title: An Object-Oriented Model for Nitrogenous Pollutants from Swine Waste Land Application
Investigators: Whalen, Stephen C. , Jeffries, Harvey E. , Miller, C. T.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Packard, Benjamin H
Project Period: March 20, 2000 through March 19, 2003 (Extended to March 19, 2004)
Project Period Covered by this Report: March 20, 2000 through March 19, 2001
Project Amount: $345,533
RFA: Computing Technology for Ecosystem Modeling (1999) RFA Text | Recipients Lists
Research Category: Environmental Statistics
Objective:
The overall objective of this work is to develop an object-oriented simulation model component for nitrogen transformations occurring in agricultural fields fertilized with liquid lagoonal swine effluent. Specific goals are to: (1) collect empirical data regarding microbial nitrogen transformations in receiving soils for processes that are insufficiently understood to adequately model; (2) design a soil modeling component that will interface with atmospheric and shallow groundwater model components; (3) utilize representations for transport, exchange, and reactions that can be efficiently solved by object-oriented numerical methods; and (4) provide for easy modification of the object system to accommodate a range of representations from explicit to generalized, depending upon evolving knowledge of the processes and availability of instance data.Progress Summary:
Empirical Studies. Immediately upon application to spray fields, N loss is incurred by ammonia volatilization and denitrification. The latter process involves emission of nitrogenous gases as N2 and N2O. Nitrous oxide emission accounts for about 1.4 to 2.0 percent of the end product of denitrification, but is significant from the standpoint that it is considered to be a greenhouse gas. Both the emission ratio of N2O/N2 and the rate of denitrification are highly dependent on soil moisture. Accordingly, time courses for emission following waste application show peak emission shortly after fertilization and a slow return to baseline emissions after about 2 weeks. Rates of nitrification also are moisture dependent. Laboratory studies with intact cores and homogenized soil samples show that nitrification increases with soil moisture to about 45 percent water holding capacity and decreases again as soil moisture increases above this value. Both nitrification and denitrification show a strong temperature dependence. Laboratory experiments with homogenized soil samples show a temperature optimum of 33 C for nitrification and 50 C for denitrification. Temperature coefficients (Q10 values) for nitrification and denitrification were 3.2 and 1.9, respectively.Modeling Studies. Modeling studies have proceeded along two lines:
testing various formulations of the nitrogen pools and their transformations;
and modifying and expanding a geographic information system-based hydrological
ecosystem model to be more object oriented and to permit many forms of soil
processes to be easily included in the model. The ecosystem model is the RHESSYS
model, and information on the base model is available at http://www.unc.edu/depts/geog/them/models/rhessys6.html
.
Information on our redesign and conversion to an object-oriented model is
available at
http://airchem.sph.unc.edu/research/modeldevelop/soilnitrogen/.
Formulations of soil nitrogen transformations have been investigated and
initially tested using modeling building prototype software. As these are
evaluated with the empirical data and reformulated, they will be converted into
C++ code for incorporation into the RHESSYS model.
Project Research Issues. Our previous empirical research has focused on rates of two important microbial nitrogen transformations in spray fields?nitrification and denitrification?and on documenting environmental influences (e.g., soil moisture, temperature, loading rate) on these rates in field and controlled laboratory settings. We currently are assessing rates and environmental drivers for other important nitrogen transformations in spray fields, namely mineralization and plant and microbial assimilation of field-applied waste and volatilization of ammonia from field-applied waste. This research is being conducted with support from this and other grants. This empirical information is necessary for model development.
Our previous modeling research has focused on atmospheric chemistry modeling and air quality simulations. Our existing object-oriented atmospheric chemistry software system, Morpho, can be used to simulate the nitrogen chemical transformations. This is somewhat overkill for this need, however, and new code modules will be written specifically for the nitrogen transformations.
Future Activities:
During the next year, we will continue efforts to develop an object-oriented simulation model component for nitrogen transformations occurring in agricultural fields fertilized with liquid lagoonal swine effluent.Journal Articles:
No journal articles submitted with this report: View all 3 publications for this projectSupplemental Keywords:
hydro-ecosystem modeling, swine waste, nitrogen., RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Geographic Area, Water, State, Ecosystem Protection, Chemistry, Biology, Environmental Chemistry, Ecosystem/Assessment/Indicators, computing technology, Monitoring/Modeling, Ecological Effects - Environmental Exposure & Risk, Hydrology, Nutrients, Wet Weather Flows, stream ecosystems, agricultural discharges, ecological risk assessment, non-point sources, water quality, stream degradation, fertilizer, nitrogen pollutants from swine, aquatic ecosystem, agricultural watersheds, risk assessment, data management, hypoxic zones, streams, field data interpolation methods, process based simulation model, fate and transport, aquatic degradation, groundwater, agricultural runoff, hydrological stability, ecological exposure, North Carolina (NC), component-based software, surface water object-oriented modeling system, farming, agriculturally impacted watershed, chemical transport, land use model, ecosystem risk management, information technology, field scale process model, land management, anoxia/hypoxia, nitrogen runoff from farms, computer science, ecosystem modeling, downstream effects, runoff, surface water, watershed, anthropogenic stress, ecological impacts, ecological modelingRelevant Websites:
http://www.unc.edu/depts/geog/them/models/rhessys6.html
http://airchem.sph.unc.edu/research/modeldevelop/soilnitrogen/
http://airchem.sph.unc.edu/research/modeldevelop/morpho/
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.