Predicting Trace Element Bioavailability in Contaminated Soils.

Trace element bioavailability in contaminated soil depends on the contaminant speciation as well as soil chemical properties.  Because measurement of the bioavailable fraction using bioassays is time-consuming and expensive, chemical methods are being developed to estimate the bioavailable fraction.  These chemical methods attempt to measure trace element exposure not the bioavailable absorbed dose.   Results from chemical methods have been termed “bioaccessible” or “available” to avoid confusion with “bioavailable.”  Extensive progress has been made in method development to measure bioaccessibility of Pb and As in contaminated soils.   An essential prerequisite of chemical methods is bioaccessibility measurements need to be well correlated with an acceptable bioavailability assay, and the simpler, the better.  Trace element bioavailability to plants can be estimated by a variety of soil chemical extraction methods including neutral salt extractions.  In vitro gastroinestinal methods have been developed to measure bioaccessible Pb and As and estimate human exposure via soil ingestion.  The ability of developed soil chemical methods to predict trace element bioavailability, outside of the limited set of soils used to develop the method, is very limited.  We will report the ability of commonly used soil chemical methods to predict trace element bioavailability in contaminated soils.