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Environmental fate & pathways

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For the partitioning of cyanides in the environment, only the distribution of hydrogen cyanide (HCN) is relevant. Sodium cyanide, potassium cyanide and acetone cyanohydrin all hydrolyse and release HCN, which is the substance of concern (ECETOC, 2007).

The Henry's Law Constant for HCN of 13.48 Pa m3/mol indicates that hydrogen cyanide is volatile and will partition from water into air. The Koc for hydrogen cyanide of 2.71 L/kg is similar to the modeled Koc value of 2.841L/kg for sodium cyanide and potassium cyanide, and indicates that even when cyanide salts are evlauated as free cyanide, the partitioning to organic carbon is not susbstantial. Adsorption to sediments or suspended solids is unlikley to be significant, primarily due to the high solubility of cyanides in water.

Level III fugacity modeling indicates that cyanide discharged into surface water will remian largely in surface water at compartmental transfer equilibrium, and the partition equilibrium will never be achieved. Likewise, cyanide discharged into air will remain largely in the air. Therefore, the concentration ratios of mass trasfer are dependent upon whether the input is to air or water.