Bioaccumulation of Inorganic Chemicals from Soil by Plants: Spiked Soils vs. Field Contamination or Background

ABSTRACT

Risk assessors are often cautioned against the use of tests of highly bioavailable salt solutions added to soil to estimate the bioaccumulation of chemicals from waste site soils by plants. In this investigation, a large number of laboratory and field studies that measured the bioaccumulation of inorganic chemicals in plants were reviewed. The objective was to discern whether or not the relationship between the concentration of the element in aboveground vegetation and that in soil was different if the contamination was aged in the field rather than freshly added to soil in salt solution. For two of the eight elements, selenium and cadmium, salt solution experiments were associated with greater soil-plant uptake ratios than field measurements. Thus, these are not reliable data for use in the derivation of plant uptake regressions for screening-level ecological risk assessments at field sites. In contrast, the plant uptake of arsenic, copper, lead, mercury, nickel, and zinc, when added in salt solutions, was generally within the 95% prediction limit of regressions derived from field data. Chemical form, plant taxon, soil type, experimental methodology, and aging may be as important as the source of the chemical in predicting plant uptake of inorganic chemicals from soil.

Keywords:

• ecological risk assessment
• plant uptake
• bioaccumulation
• metals
• bioavailability
• soil.

ACKNOWLEDGMENTS

All authors were staff at ORNL when this work was performed. This research was sponsored by the U.S. Department of Energy Oak Ridge Operations Office, Environmental Management Program, and performed at ORNL. ORNL is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. Michael Aplin and M. Elizabeth Will compiled some of the data for this study. We thank Daniel S. Jones, Jim Loar, and Christopher Welsh from Oak Ridge National Laboratory for comments on earlier drafts of this manuscript.

This article has been authorized by a contractor of the U.S. government under contract No. DE-AC05-00OR22725. Accordingly, the U.S. government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. government purposes.

Notes

^†Model: ln (conc. in aboveground plant) = B0 + B1 (ln [conc. in soil]), where concentrations (mg/kg) are expressed on a dry weight basis.

^††These values were entered incorrectly in Table 2 in Efroymson et al. (2001). An erratum has been published in Environ Toxicol Chem 5: 1177.

1 Insufficient risk assessment data are available to determine how often the screening-level soil concentrations for wildlife that are derived using the 95% upper prediction limit for the regressions in Efroymson et al. (2001) do not exceed concentrations of background elements in soil.