Isotopic Fingerprints of Iron-Cyanide Complexes in the Environment.

Tracing the origin of iron-cyanide complexes in the environment is important because these compounds are potentially toxic. We determined the stable isotopic compositions of cyanide-carbon (CCN) and cyanide-nitrogen (NCN) in 127 contaminated solids and 11 samples of contaminated groundwater from coal carbonization sites, blast furnace operations, and commercial cyanide applications. Coal-carbonization-related cyanides had unique high mean δ(13)CCN values of -10.5 ± 3.5‰ for the solids and -16.1 ± 1.2‰ for the groundwater samples, while the values for blast furnace sludge (-26.9 ± 1.5‰), commercial cyanides (-26.0 ± 3.0‰), and their corresponding groundwaters were significantly lower. Determination of δ(13)CCN is a promising tool for identifying the source of cyanide contamination. However, for coal carbonization sites, historical research into the manufacturing process is necessary because a nonconventional gas works site exhibited exceptionally low δ(13)CCN values of -22.7 ± 1.7‰. The δ(15)NCN values for samples related to coal carbonization and blast furnaces overlapped within a range of +0.1 to +10.3‰, but very high δ(15)NCN values seemed to be indicative for a cyanide source in the blast furnace. In contrast, commercial cyanides tend to have lower δ(15)NCN values of -5.6 to +1.9‰ in solids and -0.5 to +3.0‰ in the groundwater.