Grantee Research Project Results
Final 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 Amount: $345,533
RFA: Computing Technology for Ecosystem Modeling (1999) RFA Text | Recipients Lists
Research Category: Environmental Statistics
Objective:
The overall goal of this work was to create and evaluate an object-oriented simulation model for nitrogen (N) species transport and transformations occurring in soils used as spray fields for liquid swine waste at a large-scale hog production facility. The specific objectives of this research project were to: (1) create a high-level object-oriented representation of nitrogen cycling in the environment; (2) develop a specific object-oriented model capable of simulating fluid flow and N species transport in an unsaturated porous medium system; (3) collect detailed and comprehensive field data that are consistent with practices applied at a regionally representative confined animal feeding operation (CAFO) in the southeastern United States; (4) perform controlled laboratory measurements in support of the field-based determinations to allow for more complete and conclusive interpretations to be made; and (5) use the specific object-oriented model to simulate N transport and fate in an unsaturated porous medium system.
Summary/Accomplishments (Outputs/Outcomes):
This work produced significant results in three main areas: (1) object-oriented design of a regional-scale hydroecological model; (2) the development of a specific object-oriented mechanistic model to describe two-phase flow in the unsaturated zone and movement, reactions, and fate of N in the shallow subsurface; and (3) extensive laboratory and field data supporting the transport and fate of N resulting from the disposal of swine waste. Comparisons between the mechanistic N transport and fate model and experimental data showed a reasonable agreement.
The object-oriented design portion of this work is an important demonstration of the significant effort and steps involved in moving legacy environmental models based on a procedural paradigm to a modern object-oriented framework. For large models, the effort needed to accomplish this design is significant. Our experience in this endeavor should enable others to accomplish such tasks more easily. The rewards for doing so is a model that is more easily understood, maintained, and extended, which is the holy grail of object-oriented methods. We believe this is a realistic goal, but one that requires considerable expertise and effort to realize—parts of the story that often go either unrealized or untold.
The specific mechanistic model of N transport and fate is the most sophisticated such model developed to the best of our knowledge. This model includes multiphase fluid flow; species transport by advection, dispersion, and diffusion; interphase mass transfer processes; and a complex set of reactions believed to describe reasonably the N cycle in a natural environment. State-of-the-art, object-oriented numerical methods were used to approximate this model, and these methods will allow for the maturation and extension of this research code in the future as additional observations become available to test this model in a more complete fashion. Because it is a true-to-mechanism model, realistic simulations require parameter values to describe the many operative processes. This is not a limitation of the model, only an acknowledgment of the effort and obstacles facing realistic simulation of N transport and fate in natural environments.
The experimental data collected during this project are significant and are the most complete account of N transport and fate resulting from liquid swine waste application to a land surface in the southeastern United States. Swine-producing CAFOs have proliferated in this region in the past 20 years, and the fate of N in lagoon-spray field systems has been largely undocumented, as it differs from the waste management techniques employed in the Midwest. A wide variety of methods were used to quantify the many species, concentrations, and fluxes of concern in experimental field fertilizations. Further, the effects of temperature and moisture on microbial processes central to N cycling dynamics were assessed under controlled laboratory conditions. These results show that nitrification occurs rapidly in the unsaturated zone, denitrification occurs to a significant extent only at saturation levels at or above the field capacity, and that the sites examined are well-adapted nitrifying systems in which plant growth and volatilization consume the majority of the applied N in most instances.
The model is in agreement with the data collected using our best estimates of unmeasured parameter values. The model provides a tool to further examine experimental data and to provide feedback regarding the most important parameters expected to affect N cycling in the unsaturated zone. This model also has the potential for providing guidance to develop best management practices to limit the degradation of groundwaters.
Additional publications detailing the mechanistic model and the detailed field and laboratory data collected will be submitted in the coming months.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 3 publications | 1 publications in selected types | All 1 journal articles |
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Fischer EN, Whalen SC. Rates and controls on denitrification in an agricultural soil fertilized with liquid lagoonal swine waste. Nutrient Cycling in Agroecosystems 2005;71(3):271-287. |
R827955 (Final) |
not available |
Supplemental Keywords:
air, leachate, chemical transport, bacteria, waste minimization, environmental chemistry, biology, ecology, hydrology, modeling, monitoring, southeast, agriculture,, 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 modelingProgress 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.