Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:14:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 14 (pt 3/9)
Character Range: 2338719–2341604

respect to phase partitioning from volatile organics. Phase partitioning (and speciation) depends on the soil pH, ionic strength, complexation and the presence of sunlight (Larsen 2005). As noted by RIVM (2001), little HCN gas has been reported at sites where cyanide (free and/or complexed) is present, particularly sometime after disposal of cyanide wastes.  In addition the validity of standard volatilisation models such as the Johnson & Ettinger model (J&E from US EPA 2003) for free cyanide needs to be determined. A more detailed review of free cyanide and relevance of standard vapour models was conducted by RIVM (2001), where the model VOLASOIL (similar to the J&E model) was reviewed in conjunction with field data. It was concluded that HCN gas concentrations in air due to soil contamination are too complex to predict as too many soil factors are involved.  On the basis of the above, the generation of HCN gas has not been considered in the derived HILs. The potential presence of HCN gas (and potential inhalation exposures) should be addressed on a site-specific basis.

    14.3.5     Plant Uptake
There is little information available on the presence of free cyanide and cyanide species in plants grown on cyanide-affected soil. Similarly, limited data is available on the concentration of free cyanide and cyanide species in different parts of plants. The most relevant information available relates to phytotoxic levels of cyanide. Based on the available information, RIVM (2001) estimated that the maximum concentration that may be present in plants grown in contaminated soil is 1 mg free cyanide/kg produce. At concentrations higher than this, plants are most likely to be unhealthy, hampered in their growth and not suitable for consumption. In addition, the maximum concentration of free cyanide in soil not affecting seed emergence is 15 mg/kg soil, with laboratory studies showing 27 mg free cyanide/kg soil is phytotoxic to plants.

Free cyanide does not accumulate in healthy plants, with practically all free cyanide taken up by healthy plants converted to asparagines (provided phytotoxicity does not occur). Based on the above, plant uptake of free cyanide is not considered significant and has not been considered in the derivation of HIL A.

Note that there are some cyanogenic plants that release elevated concentrations of free cyanide upon damage to their plant cells (RIVM 2001). The presence of these plants and the phytotoxicity of free cyanide should be considered in any site-specific assessment.

    14.3.6     Intakes from Other Sources – Background
Some levels of cyanide and free cyanide in the Australian environment are provided in the review undertaken by NICNAS (2010). In general, cyanides can occur naturally at low concentrations in ground and surface water with the ADWG (NHMRC 2011) noting that naturally occurring free cyanide