Determining the Bioavailability, Toxicity and Bioaccumulation of Organic Chemicals and Metals for the Development of Eco-SSLs
ER-1210
Objective
Schematic of Chemical Bioavailability in Soils
Ecological soil screening levels (Eco-SSLs) are soil concentrations of chemicals which, when not exceeded, will theoretically protect terrestrial ecosystems from unacceptable harmful effects due to chemicals. Although soil screening levels are available for human risk assessment, Eco-SSLs are only currently being developed. They are derived using data generated from laboratory toxicity tests with many different test organisms which theoretically represent the vast array of naturally occurring ecological receptors. Even though research has shown that the bioavailability of chemicals to organisms in soil is substantially less than 100 percent, it is assumed that all the chemical in soil is bioavailable to soil invertebrates and plants during the derivation of Eco-SSLs. Bioavailability of chemicals to organisms in soil is modified by a vast array of physical, chemical, and biological modifying factors. In order to screen contaminated sites for the ecological risk assessment process, it is necessary to develop rapid, inexpensive, routine methods for measuring the bioavailability of chemicals for plants and soil invertebrates.
The objective of this project is to address how chemical bioavailability and toxicity to soil invertebrates and plants is modified by soil physical/chemical properties and how bioavailability can be measured in soil systems for compounds of concern to terrestrial ecosystems, including polycyclic aromatic hydrocarbons (PAHs), 2,4,6-trinitrotoluene (TNT), hexahydro-trinitro-triazine (RDX), cadmium (Cd), lead (Pb),arsenic (As), and zinc (Zn).
Technical Approach
This project will involve the spiking of chemicals to soils varying in physical/chemical parameters. Spiked soils will be subject to wet/dry cycles and chemical availability will be monitored over time to ensure that rapid soil/chemical interactions have occurred prior to conducting bioassays. Bioassays will be conducted with earthworms, enchytraeids, Collembola, and a number of plant species. Endpoints monitored during the bioassays will include reproduction for invertebrates and germination and early seedling growth for plants. Chemical exposure will be expressed as total chemical concentration and also using measures more reflective of the level of chemical bioavailable to test organisms. Solid-phase extraction techniques will be used as measures of bioavailability for organic compounds, while sequential extraction techniques ranging from weak salt solutions to digestion with nitric acid will be used for metals. Chemical bioavailability will also be determined through residues in the organisms, both in terms of bioaccumulation (non-toxic levels) and residues associated with sublethal effects such as growth and reproduction (critical body residues). Multiple regression models will be developed to describe empirical relationships between soil physical/chemical characteristics and toxicity and/or bioaccumulation in soil invertebrates and plants.
Benefits
The development of a model relating soil physical/chemical characteristics to the bioavailability, bioaccumulation, and toxicity of TNT, RDX, PAHs, and selected metals to soil invertebrates and plants will allow the incorporation of bioavailability into the development of Eco-SSLs. Sound, scientifically based Eco-SSLs will allow a rapid initial screening of contaminated Department of Defense, Department of Energy, and Environmental Protection Agency sites and removal of low-risk sites from further ecological risk assessment. This will allow efforts and resources to be focused on sites that present an unacceptable risk to ecosystems.
Points of Contact
Principal Investigator
Mr Roman Lanno PhD
Ohio State University
Phone: 614-292-4943
Fax: 614-292-2180
Document Types
- Fact Sheet - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
- Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
- Model/Software - Computer programs and applications available for download.
- Database - Digitally organized collection of data available to search and access.