Tuesday, November 6, 2007
231-17
Soil Properties and Ecological Risk Assessment of Arsenic Contaminated Soil: Phytotoxicity Adjustments using Plant Metal Upper Critical Values.
Richard H. Anderson and Nicholas T. Basta. School of Environment and Natural Resources, Ohio State University - Columbus, 2021 Coffey Rd, Columbus, OH 43210-1085
Hazardous effects of environmental contaminants on non-human receptors are the focus of ecological risk assessments. Soil matrix properties can mitigate hazardous effects of contaminants through soil chemical sequestration and should be considered when evaluating ecological risk from terrestrial contamination. Empirical models that quantify relationships between chemical/physical properties of soils and hazardous effects of contaminants, such as toxicity, can improve the accuracy of ecological risk assessments. However, differential sensitivities of organisms to various environmental contaminants often inhibit the utility of such models because of the introduction of additional variability. We present a novel approach to dose/response toxicity parameter estimation that normalizes estimates by partitioning the effect due to differential sensitivities of test organisms from that of soil chemical/physical properties. Five soils that ranged in chemical/physical properties were spiked with five concentrations of sodium arsenate. Bioassays were conducted where above ground dry matter growth (DMG) and the corresponding tissue As concentration were evaluated for three terrestrial plants (Alfalfa, Medicago sativa; Perennial ryegrass, Lolium perrene; and Japanese millet, Echinochloa esculenta) each with different sensitivities to As (V). Conventional toxicity parameters and threshold tissue As concentrations which initiated a decline in DMG were estimated for each plant. Threshold tissue As concentrations were estimated using a plant metal upper critical value (PMUCV) algorithm and used to normalize conventional toxicity parameter estimates. The normalization technique and results are discussed within the context of the mitigating effect of soil properties on As phytotoxicity. Adjustment of ecotoxicity parameters by PMUCV is a promising approach to account for soil As (V) sequestration.