An Object-Oriented Model for Nitrogenous Pollutants from Swine Waste Land Application

EPA Grant Number: R827955
Title: An Object-Oriented Model for Nitrogenous Pollutants from Swine Waste Land Application
Investigators: Whalen, Stephen C.
Current 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


Agricultural nonpoint source pollutants are increasingly problematic with respect to air quality in North Carolina and other southeastern states. Estimates for North Carolina are that 96% of stream degradation is caused by nonpoint source pollutants and that agriculture is responsible for 67% of that total. Agriculture has been implicated in the deterioration of water quality in the Neuse River and Albemarle-Pamlico watershed through fertilizer-N loss to surface waters and atmospheric transport of volatilized NH3 to downwind waters. Attention has focused on large scale swine production as a nonpoint agricultural N source for coastal rivers and waters. North Carolina presently ranks second among swine producing states. About 101,000 ha of land are devoted to spray fields on 2450 permitted swine production facilities. The extant population of 10 million head generates 48 Gg N per year in waste. Field-applied waste is volatilized as NH3, assimilated into plant matter, mineralized or transformed by microbes or enters surface and ground waters. Accurate description of N fluxes and transformations is necessary to implement management practices that minimize offsite nutrient transport.

The aim of this work is to develop an object-oriented simulation model component for nitrogen transformations occurring in agricultural soils fertilized with liquid swine waste. Accordingly, it is necessary to: 1) design within a modeling framework that permits the soil model to interface with atmospheric and shallow groundwater components; 2) utilize representations for transport, exchange, and reactions that can be efficiently solved by object-oriented numerical methods; and 3) 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.


An effective collaboration on multimedia modeling exists in North Carolina. Model structure, interfaces, and solution methods specifications are evolving. Once object interfaces and numerical implementation objects are agreed upon, sub-domain specific model formulation and testing can proceed independently via replaceable implementation of the component-to-component interfaces with loose coupling techniques such as lookup tables or field data interpolation methods. Our previous research has produced field data sets from typical operating farms and laboratory data generated with soil from same. These data reveal enough about the processes and transformations that will permit us to produce a process-based simulation model (which will of necessity have several parameterized representations) for the transformation and exchange of gaseous- and aqueous-borne N, including NH3 volatilization, conversion to N2 and N2O, assimilation into biomass, surface runoff and infiltration into shallow groundwater.

Expected Results:

The primary result will be a C++ computer code implementing the model component and its test framework. Additionally, peer-reviewed publications will result from model formulation and evaluation. The primary benefits from these results will be advancing knowledge, improving predictive capability and reducing uncertainty with risk-based models. The correct assessment of risk to ecosystems from multimedia impacts is important in deciding on appropriate regulations. Our work will improve the ability to forecast such exposure.

Publications and Presentations:

Publications have been submitted on this project: View all 3 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 1 journal articles for this project

Supplemental Keywords:

multimedia, interdisciplinary, hypoxia, anoxia, water quality, finite volume, Neuse River, groundwater., RFA, Scientific Discipline, Geographic Area, Water, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Hydrology, Ecosystem/Assessment/Indicators, Ecosystem Protection, Environmental Chemistry, State, Chemistry, Ecological Effects - Environmental Exposure & Risk, Monitoring/Modeling, computing technology, Wet Weather Flows, Biology, ecological risk assessment, fate and transport, risk assessment, agricultural runoff, aquatic ecosystem, anthropogenic stress, ecosystem modeling, agriculturally impacted watershed, hydrological stability, ecological exposure, farming, streams, watershed, field scale process model, agricultural discharges, field data interpolation methods, land use model, ecosystem risk management, runoff, surface water object-oriented modeling system, stream ecosystems, downstream effects, ecological modeling, computer science, chemical transport, surface water, agricultural watersheds, fertilizer, aquatic degradation, nitrogen pollutants from swine, nitrogen runoff from farms, data management, ecological impacts, hypoxic zones, anoxia/hypoxia, component-based software, information technology, non-point sources, water quality, North Carolina (NC), stream degradation, groundwater, land management, process based simulation model

Progress and Final Reports:

  • 2000 Progress Report
  • 2001
  • 2002
  • Final Report