No abstract

Water-soluble iron cyanide compounds are widely used as anticaking agents in road salt, which creates potential contamination of surface and groundwater with these compounds when the salt dissolves and is washed off roads in runoff. This paper presents a summary of available information on iron cyanide use in road salt and its potential effects on water quality. Also, estimates of total cyanide concentrations in snow-melt runoff from roadways are presented as simple mass-balance calculations. Although available infoffilation does not indicate a widespread problem, it also is clear that the water-quality effects of cyanide in road salt have not been examined much.Considering the large, and increasing, volume of road salt used for deicing, studies are needed to determine levels of total and free cyanide in surface and groundwater adjacent to salt storage facilities and along roads with open drainage ditches. Results could be combined with current knowledge of the fate and transport of cyanide to assess waterquality effects of iron cyanide anticaking agents used in road salt. Water Environ. Res .. 7], 1235Res .. 7], (1999.

The oxidative dissolution of pyrite (FeS 2 ) is difficult to study because of redox transformations of the iron and sulfur, and adsorptive and precipitative loss of products from solution. Quantitative measurement of pyrite dissolution can perhaps be done most accurately with electrochemical techniques, but monitoring of dissolution products is of interest for interpretation of water-quality data at mine drainage and other field sites where pyrite dissolution is occurring. This laboratory study was undertaken to assess the usefulness of the sum of sulfate, sulfite, and thiosulfate in solution as a reaction progress variable, or RPV, for abiotic pyrite dissolution. Sulfate was the only sulfur species detected in solution, and thus was chosen as the RPV. Previous investigators have demonstrated that ferrous iron is not reliable as an RPV because of adsorption to the pyrite surface. Results indicated that sulfate is also not a highly accurate RPV. There was a sulfate loss from solution, perhaps by adsorption, with the extent of loss varying with solution conditions. While not a highly accurate RPV for kinetics modeling, the sulfate concentration provided a measure by which relative rates of abiotic pyrite dissolution could be assessed for pH 3 and 6, and with oxygen and ferric iron as oxidants. Sulfate production was greatest at pH 6 in the presence of oxygen, but no sulfate was produced under anoxic conditions (Fe 3ϩ added as oxidant) at the same pH. The sulfate release under oxic conditions at this circumneutral pH was an order of magnitude greater than the release at pH 3 under both oxic and anoxic conditions.