05-CBRC-E18
Field Testing of Arsenic and Mercury Bioavailability Model from Land-Applied Coal Combustion Byproducts

The U.S. Environmental Protection Agency classifies coal combustion byproducts (CCBs) as non-hazardous, and a number of states including Alabama, Kentucky, and Tennessee allow land application of CCBs without any regulatory issues.  However, perceptual and regulatory barriers still exist for the use of CCBs for application to agricultural land.  One concern is the lack of information regarding the environmental effects of CCB use, including the potential bioavailability of contaminants to soil organisms, plants, and possibly animals and man.  With increasing amounts of FGD (flue gas desulfurization) being produced, along with fly ash, application of CCBs for enhancing agricultural land is one solution for reducing the amount that has to be stored on-site.  In addition, application of CCBs to soil can provide a number of benefits for soil improvement, and consequently, to plant growth and crop yields.  This researcher proposes to develop a model to predict plant bioavailability of arsenic (As) and mercury (Hg) on soil amended with fossil plant CCB.  Tennessee Valley Authority (TVA) is currently conducting a greenhouse study for development of a model for plant uptake on soil amended with FGD scrubber gypsum, followed by a field study to assess the ability of the greenhouse models to accurately predict uptake of trace elements in the field.  For model development in the greenhouse study, soil will be analyzed using a sequential extraction procedure to determine the amount of As and Hg in various soil fractions, and this will be used as input for a multiple-variable regression model to determine the soil fractions that contribute significantly to plant uptake.  This would provide a rapid method for estimating bioavailability of As and Hg in a large number of amended soils, as opposed to growing plants to maturity for contaminant uptake.  Modeled predictions of the environmental fate of As and Hg will provide greater flexibility for offsite land application uses.  This will allow the fossil power industry greater latitude in promoting the marketing and utilization of these materials for beneficial reuse in agricultural applications, which may result in operation and maintenance cost savings or in avoided costs for on-site storage.

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