Speciation of selected trace metals in drilling wastes and their potential for migration in alluvial soil

The goal of this research was to develop an understanding of trace metal speciation in waste drilling fluids and oil field produced wasters, and to develop insights into transport and fate as a function of trace metal speciation.;Three waste drilling fluids and produced waters were taken from sites in Wyoming, and because of the low concentrations of the trace metals of interest, the fluids were spiked with ionic forms of Ba, Cd, Cr, Pb, and Zn. After equilibration, total metals concentrations were determined analytically. Aliquots of the fluids were passed through Bio-Rad Laboratories Chelex-100 and AG1-X8 ion exchange resins in a column exchange procedure. The exchangeable species fractions were then determined. The fraction not exchanged on either resin was determined by difference. Subsequent to the initial species characterization of the fluids, the retardation phenomena and species distribution while being transported through bentonitic waste drilling solids-lined fluid impoundments and alluvial soil was modeled in the laboratory by the use of columns. Column influent and effluent aliquots were analyzed for iron, zinc, and the trace metals of interest. General chemical parameters, major ion analyses, and trace metal analyses were performed by common wet chemistry, flame atomic absorption, and ICP methods.;The major conclusions reached were: (1) differences in speciation of trace metals do exist between different fluids; (2) peak concentrations of barium above the MCL for this element in drinking water were found in one of the three fluids tested, even though the influent barium concentration was 50 percent of the MCL; (3) speciation of trace metals in soil column effluents was a function of changes of the fluid's chemistry caused by interactions with the porous media and the pre-existing pore fluid rather than a function of the influent speciation; and (4) transport or non-transport of an element was found to be a function of the speciation of the element and its geochemical environment.