United States Environmental Protection Agency Office of Research and Development National Exposure Research Laboratory Research Abstract Government Performance Results Act Goal: Sound Science Significant Research Findings: A Computer Model for Predicting Chemical Properties and Environmental Behaviors Scientific Problem and Increasingly, the U.S. EPA will have to rely on predictive modeling Policy Issues technologies to conduct the complex array of exposure and risk assessments needed to prepare scientifically sound regulations. The need for multimedia, multistressor, multipathway assessments, from both human and ecological perspectives, over broad spatial and temporal scales, places a high priority on the development of broad new modeling tools. However, as this modeling capability increases in complexity and scale, so must the model inputs. These new models will require huge arrays of input data, and many of the required inputs are neither available nor easily measured. In response to this need, researchers at NERL-Athens have developed a predictive modeling system, SPARC (SPARC Performs Automated Reasoning in Chemistry), which calculates a large number of physical/chemical parameters from pollutant molecular structure and basic information about the environment (media, temperature, pressure, pH, etc.). The SPARC system has been under development for several years and currently calculates a wide array of physical/chemical reactivity parameters for organic chemicals. Research Approach The research effort is designed to elucidate and model the underlying physical, chemical, enzymatic, and biological processes that describe the transport and fate of organic pollutants, nutrients and other stressors in environmental systems. These process models will be incorporated into the SPARC system. The SPARC model currently provides temperature- and pressure-dependent estimates for a number of parameters. These parameters can be estimated for a wide range of organic chemicals, from simple aliphatic compounds to relatively large molecular structures such as pesticides and pharmaceutical drugs. Software interfaces are being constructed to link SPARC directly to environmental systems models and thus provide not only for model parameterization but for real time upgrades of reactivity parameters during model execution. National Exposure Research Laboratory — October 2001 ------- The SPARC system has been under development for several years and provides chemical parameter input to multimedia modeling programs (Hazardous Waste Identification Rule and Total Maximum Daily Loads). Predictive models, like SPARC, permit the U.S. EPA to perform the increasingly complex exposure and risk assessments necessary to develop scientifically sound regulations that protect human health and safeguard the natural environment. SPARC research has involved an integrated effort of scientists and modelers from EPA and academia. Each process research component has science products (technical presentations, research publications, and process models). These models, along with estimation algorithms for reactivity constants, are incorporated into SPARC. Completed SPARC models are available to modeling clients online at http://ibmlc2.chem.uga.edu/sparc/style/welcome.cfm. Examples of recent publications from this study include: Hilal, S.H., Carreira, L.A., and Karickhoff, S.W. "Esimation of Physical Properties in Solution for Organic Compounds." Quant. Struct. Act. Relate (Submitted). Hilal, S.H., Carreira, L.A., and Karickhoff, S.W. "Estimation of Physical Properties in the Gas Phase for Organic Compounds." Quant. Struct. Act. Relat. (In Press) Hilal, S.H., Carreira, L.A., and Karickhoff, S.W. "A Comprehensive Study of Molecular Speciation: Calculation of Microscopic and Zwitterionic Ionization Constants." Talanta 827:50, 1999. Future Research Future research will focus on extending, refining and testing of current SPARC models. Specific activities will include 1) developing methods for measurement and prediction of tautomeric speciation, 2) developing models for biotic and abiotic reduction, 3) developing descriptive/predictive models for biogeochemical processes in soil/sediment systems, and 4) constructing/implementing a software interface to dynamically link SPARC to the oil plume model Lens3. New research areas this Fiscal Year include 1) measurement and prediction of chemical hydration, 2) developing models for chemical hydrolysis, and 3) constructing a generic software interface to dynamically link SPARC to multimedia models. Results and Implications Research Collaboration and Publications National Exposure Research Laboratory — October 2001 ------- Contacts for Contacts for Additional Information: Additional Information J. MacArthur Long U.S. EPA, Office of Research and Development National Exposure Research Laboratory 960 College Station Road Athens, Georgia 30605-2700 Phone: 706/355-8200 E-mail: long.macarthur@epa.gov National Exposure Research Laboratory — October 2001 ------- |