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Selenium leached from coal tailings and spoil is a challenge for mining operations in southern West Virginia. Selenium discharges are not supposed to exceed 5 lg/L, and yet are commonly in the range of 10-25 lg/L. Once in the selenate form, selenium removal can be extremely difficult and expensive, particularly in the narrow valleys and highly variable flow regimes of southern West Virginia. This study reports on the first 96 weeks of a leaching study. Selenium leached at the rate of 0.06% of the extant selenium pool per day. After 96 weeks, about 35% of the original, potentially mobile selenium had leached. While sulfur was far more abundant, its leach rate was about 10% of the selenium rate. Iron oxyhydroxide was found to reduce the concentration of dissolved selenium by about 70%, which indicates that selenite is the dominant, mobile selenium species during initial weathering, and that selenium could be controlled at its source, through special handling and treatment of selenium-rich rock units. Iron oxyhydroxide kept selenium near the regulatory limit of 5 lg/L throughout the experiment.

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R e vMgh-perfonnance liquid Chromatography wlth ultraviolet detection can be used to determine trace levels of Pt(II), Pd(II), Rh(III), Co(III), Ru(III), and I r in aqueous solution following complexation with dlethyidithlocarbamate. The metal Complexes are extracted into acetonitrile from aqueous solution by the addition of a saturated salt solution. Quantitative metal recovery from aqueous solution is achievable for most metals for a wide solution pH range. Detection limits for the metals are <3 ng of metaMmL of original aqueous sample. Analyses of real samples are highly reprodudbile and sensitive. I r can interfere in the determination of Pt(1I) and Rh( I I I). A general protocol for chromatographic separation and determination of Pt( I I), Pd( I I ) , Rh( I I I), Ru( I I I), and I r in aqueous solution Is presented.The use of dithiocarbamates for the determination of trace-level amounts of metals by chromatographic techniques has become popular in recent years. The ability to separate metal-dithiocarbamate complexes by high-performance liquid chromatography (HPLC) has been well documented (1-3). The actual application of dithiocarbamates for real sample analysis by chromatographic methods has also been addressedThe formation of metal-dithiocarbamate complexes for chromatographic separation has been carried out in three different ways. Solvent extraction for the preconcentration of trace metals from aqueous solution using dithiocarbamates has been used extensively in metal determinations by atomic absorption spectroscopy (14). 4-Methyl-2-pentanone has generally been used as the extracting solvent and is nebulized directly into a flame (15,16) or injected into a graphite furnace (17). A similar application of these solvent extraction techniques has been used to determine trace metals by liquid chromatography (4,9,10,18), generally extracting the complex into chloroform. The ultraviolet absorption spectrum of chloroform interferes with the UV detection of the complexes by HPLC and chloroform also presents solubility problems in certain reversed-phase applications; thus chloroform is usually removed by a slow vacuum evaporation and the sample is reconstituted into an appropriate solvent which can be injected into the chromatographic system.A number of workers (6, 7,18-22) add the dithiocarbamate ligand to their chromatographic mobile phase, allowing the metal-dithiocarbamate complexes to form in situ, which speeds up the analyses by avoiding solvent extraction. In situ methods have no capacity for preconcentrating the metal and are only applicable to metal species which rapidly form stable complexes in the mobile phase. The method also requires large amounts of complexing agent and the devotion of the (4-1 3).'Present address: E. I. Present address:HPLC system to metal determinations. Dithiocarbamates absorb in the ultraviolet region; thus visible detection wavelengths (which have smaller absorptivity coefficients than ultraviolet wavelengths) are required or electrochemical detection is needed.A third approach ...

High-performance iiquld chromatography with UV detection can be used to determine trace levels of Pd( I I ) and Rh( I I I) in aqueous solution after complexation with sodium diethyidithiocarbamate. Successful low-level extraction of the precious metal complexes Into chloroform depends on the ionic strength of the aqueous phase. The use of 2 M sodium bromide in the extraction step results In high efficiency of metal complex extraction (>95 % ) for Pd( I I ) and Rh( I I I). Detection limits for Pd( I I ) and Rh( I I I) from aqueous solution are 2.7 ng/mL and 2.8 ng/mL, respectively. Complexation and extractlon conditions for the determlnatlon of Pd( I I ) and Rh( I I I ) appear to have a limited pH dependence. Trace levels of Pd in Pt powder (58 pg/g) and In an aqueous Pt atomic absorption standard solution (21 ng/mL) have been determlned. A Pt/Rh alloy (90%/10%) has been analyzed for Rh content. The analyses show high reproducibility and high sensitivity. Pd( I I ) can be determined in the presence of large amounts of Pt because the Pt( I V ) diethyidithlocarbamate complex is charged and is not extracted lnto the chloroform.The analytical applications of dithiocarbamates for trace metal determinations are well documented (1-3). The ability of dithiocarbamates to form metal complexes with a large variety of trace metals and the properties of these complexes make dithiocarbamates useful reagents in trace-metal analysis. In general, metal complexes of dithiocarbamates are thermodynamically stable and their formation is kinetically fast (4). The solubility of the metal complexes is low in aqueous solution, but high in organic solvents such as chloroform and 4-methyl-2-pentanone. Solvent extraction of dithiocarbamate complexes has thus been extensively exploited as a preconcentration technique in atomic absorption spectrometry (5-7). In addition, the large molar absorptivities of metal dithiocarbamate complexes make them useful for colorimetric trace metal determinations (8).In recent years, the use of high-performance liquid chromatography (HPLC) trace-metal analysis has grown in popularity. A number of recent reviews regarding the HPLC of metal complexes has been published (9-11). The use of dithiocarbamates for the analytical determination of trace metals has been a logical progression in the analytical use of dithiocarbamates.A variety of separation conditions, detectors, and a number of different dithiocarbamates have been used. Both reverse-phase (12-18) and normal-phase (19-22) chromatographic techniques have been utilized. The method of de; tecting the eluted metal complex has also been varied. Electrochemical (23-26) and atomic spectrometric (27) detection systems have been evaluated to some extent, but UV-vis absorption is by far the most used detection method. In addition, both on-line complexation (25,26) and prechromatographic complexation and extraction procedures have been used.This work involves the low-level determination of precious metals by the HPLC of their diethyldithiocarbamate (DEDTC) complexes....