The Oak Ridge Site has identified a need to investigate the bioavailability of mercury compounds in the Oak Ridge ecosystem. DIAL scientists have performed a series of laboratory analyses and greenhouse experiments. Uncontaminated soil was obtained from Roane County, TN (near the Oak Ridge Site) and spiked with three mercury compounds (nitrate, chloride and sulfide) at low, intermediate and high loading levels. Plants were then grown in the media to evaluate the bioavailability of different mercury chemical species in the spiked soil. We have examined solution/liquid phase speciation of mercury in the spiked soil without plants and also after a growing season with Chinese brake fern plants. Redistribution and transformation of solid-phase mercury species in spiked soil were also investigated. The effects of plants and incubation time on bioavailability and stability (especially for mercury sulfide) have been examined as well. A conceptual model of mercury speciation and bioavailability in both liquid and solid phases has been proposed and comparison with initial data sets shows significant correlation. We will continue this project during the upcoming growing season and will have extensive numbers of laboratory analyses in the coming months (approximately a thousand samples have been chemically analyzed to date). We expect the outcomes of these studies will benefit our understanding of bioavailability and stability of mercury and mercury compounds in Oak Ridge soils.