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EFFECT OF SOIL PROPERTIES ON LEAD BIOAVAILABILITY AND TOXCITY TO EARTHWORMS
Citation:
BRADHAM, K. D., E. A. DAYTON, N. T. BASTA, J. SCHRODER, M. PAYTON, AND R. LANNO. EFFECT OF SOIL PROPERTIES ON LEAD BIOAVAILABILITY AND TOXCITY TO EARTHWORMS. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 25(3):769-775, (2006).
Impact/Purpose:
The objective of this task is to develop state-of-the-science methods for evaluating toxic elements. These methods will include measuring bioavailable concentrations of toxic elements as well as enhanced traditional methods. Once established, the performance of these methods will be demonstrated on a small set of samples. Procedures will be documented such that they are readily transferable to EPA and non-EPA researchers.
Specific objectives of this task include:
1) Development of more sensitive and rapid quantitative procedures for evaluating exposure to toxic elements.
2) Assessment of the bioavailability of toxic elements in environmental media using bioavailability tools.
3) Application of this data to improve the scientific basis of site and source specific risk assessments.
4) Application of these methods to fill critical data gaps identified in the aggregate/cumulative exposure and risk research area of the Human Health Risk Assessment research plan.
Description:
Soil properties are important factors modifying metal bioavailability to ecological receptors. Twenty-one soils with a wide range of soil properties were amended with a single concentration of Pb (2000 mg/kg) to determine the effects of soil properties on Pb bioavailability and toxicity to earthworms. Earthworm mortality ranged from 0% mortality to 100% acute mortality following exposure to the same total concentration of Pb (2000 mg/kg) in amended field soils. Internal Pb concentrations in earthworms ranged from 28.7 to 782 mg Pb/kg, with a mean of 271 mg Pb/kg. Path analysis was used to partition correlations, in an attempt to discern the relative contribution of each soil property. Path analysis results indicated that pH was the most important soil property affecting earthworm mortality (p < 0.01) and internal Pb (p < 0.05). Soil pH was inversely related to mortality and internal Pb. Soil pH is inversely related to soil solution Pb and Pb bioavailability. The most important soil property modifying reproduction was FEAL. Because FEAL is rich in pH dependent cation exchange sites, several soil properties including pH, FEAL and CEC have a causal effect on Pb adsorption and soluble Pb. Path analysis is useful for assessing contaminated soils with a wide range of soil properties and can assist in site ecological risk assessment and remediation decisions for contaminated sites. Soil properties are important factors modifying metal bioavailability and toxicity and should be considered in the ecological risk assessment of metals in contaminated soils.