National Exposure Research Laboratory
Computer Models
for Environmental Fate of Chemical
Pollutants: SPARC

Why Are Computer Models Needed?
In light of recent trends in environmental regulatory strategies, the U.S. EPA will have to rely
more heavily on predictive models when performing the increasingly complex exposure and risk
assessments. These are needed to develop scientifically defensible regulations that protect
human health and safeguard the environment. As the complexity and scale of exposure and risk
assessments increase, the complexity and scale of predictive models also increase. The pressing
need for multimedia (water, air, and soil), multistressor (pollutants, nutrients, etc.), multipathway
(inhalation, ingestion, and dermal contact) assessments, from both the human and ecological
perspectives, over broad spatial and temporal scales, places a high priority on the development of
new modeling tools. These new models will necessarily require huge arrays of input data, and
many of the required inputs are neither available in the published literature nor easily measured.
The SPARC model will provide much of this data.
What is SPARC?
SPARC (SPARC Performs Automated Reasoning in Chemistry) is a computer modeling system
that calculates a large number of physical and chemical properties for chemical pollutants from
their molecular structure and from basic information about the environment such as media,
temperature, pressure, and pH. SPARC research involves an integrated effort by scientists and
modelers to explain and model the physical, chemical, and biological processes that describe
what happens to organic pollutants, nutrients, and other stressors in environmental systems.
These models, along with estimation algorithms for reactivity constants, are incorporated into
SPARC. Models developed through SPARC can be used in exposure and risk assessments.
Major Products
The SPARC system has been under development for several years and currently calculates a wide
array of physical and chemical reactivity properties.  Current and future research will focus on
extending, refining, and testing of current SPARC models.  Completed SPARC models are
available on the Internet to modeling clients.

      This research is important in developing multimedia modeling technologies to carry out
       an increasingly complex array of exposure and risk assessments. These assessments are
       necessary in developing scientifically defensible regulations.
     Development of SPARC supports the U.S. EPA's goal of Sound Science through greater
      innovation to address environmental concerns.
Selected Milestones
      Upgrades of SPARC will include prototype models for abiotic reduction in sediment
      suspensions, microbial reductive transformations in sediment systems, phyto-enzymatic
      processes, and oxidative transformations in soil systems.
      U.S. EPA, Office of Research and Development, National Exposure Research
      Laboratory, Ecosystems Research Division, Athens, GA / University of Georgia,
      Department of Chemistry, Athens, GA.
 For More Information
     Mac Long
long. macarthur(@,epa. gov
     For more information:
National Exposure Research Laboratory
Ecosystems Research Division Website
     http ://www. epa. gov/athens
            To use the online SPARC Calculator, visit the UGA Website

 For more information on this and other NERL science projects, visit our Website
Website Announcement
                                          December 2001