Cyanide Management in Groundwater and Soil

Cyanide has been observed in both soil and groundwater at sites associated with aluminum smelting, manufactured gas plants (MGP), electroplating, and the mining and processing of metal ores. Cyanide is one of the most common chemicals detected at Superfund sites [1]. As discussed throughout this book, the forms of cyanide that are present in these media vary from site to site. Sites with cyanide contamination typically have groundwater with detectable concentrations of free cyanide (HCN, CN−), weak acid dissociable (WAD) metal-cyanide complexes, available cyanide, and strong-acid-dissociable metal-cyanide complexes. However, the relative proportions of these various species of cyanide vary based on the industry-specific waste type. For example, cyanide in groundwater at MGP and aluminum production sites is predominantly iron-cyanide complexes, with relatively small fractions of WAD cyanide and almost no free cyanide. In contrast, metal mining and electroplating sites usually contain larger proportions of the WAD and free cyanide in addition to the complex metal (other than iron) cyanide compounds.