Biological Uptake of chemicals by plants and animals
Concentrations of bioavailable contaminants in ambient media are needed to evaluate foodchain transfers in ecological risk assessments. The bioavailable fraction can be measured directly by collecting and analyzing plants and animals or it can be estimated. Direct measurement is the preferred approach because it contributes the least uncertainty to exposure estimates, but it may not be feasible because of a lack time, personnel, or finances to support field sampling. When direct measurement of contaminants in biota is not possible, estimation is the only alternative.
Contaminant concentrations in biota may be estimated using a variety of methods, ranging from complex mechanistic process models to simple accumulation factors. While mechanistic process models for the estimation of contaminant concentrations in biota may give more accurate estimates, they require information which is not generally available for a risk assessment.
The simplest method for estimation of contaminant loads in biota is the use of uptake or accumulation factors. Uptake factors consist of ratios of the concentration of a given contaminant in biota to that in an abiotic medium. This method is particularly useful for ecological risk assessments, because ambient media concentrations are generally available. However, the use of uptake factors depends on the assumption that the concentration of chemicals in organisms is a linear no threshold function of the concentration in soil or sediment. Despite conditions that lead to violation of this assumption, accumulation factors are commonly used in risk assessments.
Oak Ridge National Laboratory has developed a suite of regression equations for estimating chemical concentrations in biota. They are based on uptake data from published and unpublished literature. These power functions are believed to provide better estimates of contaminant loads in biota than do simple uptake factors. Distributions of uptake fators are also included for completeness
REPORTS & PAPERS [ Top ]
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Efroymson, R.A., B.E. Sample, and G.W. Suter. 2001. Uptake of inorganic chemicals from soil by plant leaves: Regressions of field data. Environmental Toxicology and Chemistry 20:2561-2571.
Sample, B.E., G.W. Suter, J.J. Beauchamp, and R.A. Efroymson. 1999. Literature-derived bioaccumulation models for earthworms: Development and validation. Environmental Toxicology and Chemistry 18:2110-2120.
Bechtel Jacobs Company LLC. 1998. Empirical Models for the Uptake of Inorganic Chemicals from Soil by Plants. Bechtel Jacobs Company LLC, Oak Ridge, TN. BJC/OR-133.
Bechtel Jacobs Company LLC. 1998. Biota Sediment Accumulation Factors for Invertebrates: Review and Recommendations for the Oak Ridge Reservation. Bechtel Jacobs Company LLC, Oak Ridge, TN. BJC/OR-112.
Sample, B. E., J. J. Beauchamp, R. A. Efroymson, and G. W. Suter, II. 1998. Development and Validation of Bioaccumulation Models for Small Mammals. Oak Ridge National Laboratory, Oak Ridge TN. 89 pp. ES/ER/TM-219.
Sample, B.E., J.J. Beauchamp, R.A. Efroymson, G.W. Suter, II, and T.L. Ashwood. 1998. Development and Validation of Bioaccumulation Models for Earthworms. Oak Ridge National Laboratory, Oak Ridge TN. 93 pp. ES/ER/TM-220 [ Report, Appendices A-D].
LINKS to RELATED SITES [ Top ]
Environmental Residue-Effects Database (ERED) - a compilation of data, taken from the literature, where biological effects (e.g., reduced survival, growth, etc.) and tissue contaminant concentrations were simultaneously measured in the same (aquatic) organism.
National Sediment Bioaccumulation Conference Proceedings Summary - view or obtain copies of the conference proceedings.