Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:9:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 9 (pt 1/2)
Character Range: 790889–793838

9                   Non-metals (cyanide and sulfur)

9.1              Cyanide (weak acid dissociable)

    9.1.1         Scope and application
Free cyanide (defined as the cyanide ion (CN-) or hydrogen cyanide (HCN)) is only formed in environments that are dominated by weak cyanidemetal complexes (for example, silver cyanide) and dissolved cyanide complexes. The presence of free cyanide in soil and the potential for formation of HCN is complex and depends on the soil pH, ionic strength and complexation.

The HIL has been derived on the basis of free cyanide and it is recognised that the measurement of free cyanide in soil is difficult, due to instability of free cyanide and also the instability of cyanide metal complexes that can produce free cyanide. A cautious approach, (Department of Resources, Energy and Tourism 2008 and ICMI 2009), is to measure not only the free cyanide but also to measure several other dissociable cyanide species that could furnish free cyanide either by dilution or by other natural processes (refer to US EPA method 9016).

The US EPA Weak Acid Dissociable Cyanide (WAD) method is a surrogate (and conservative) measure of free cyanide, due to the difficulty in measuring free CN.

    9.1.2         Principle
The US EPA Weak Acid Dissociable Cyanide (WAD) method measures free cyanide plus the cyanide associated with most unstable metal cyanide complexes. The WAD cyanide refers to any species where cyanide is liberated at pH of 4.5. Such species include HCN (aq) and CN-, the majority of Cu, Cd, Ni, Zn and Ag complexes. If the WAD result conforms to the HIL then the free cyanide level is also in compliance with the HIL.

9.2              Total sulfur

    9.2.1         Scope and application
This method (Tabatabai et al. 1988, Tabatabai 1982) is applicable to the determination of total sulfur in soil, sediment, plants and other solids.

    9.2.2         Principle
Sulfur is oxidised to the sulfate form by fusion. The sample is ignited with sodium bicarbonate and silver oxide at 550°C for three hours and the melt is dissolved in acetic acid. The resultant solution is analysed for total sulfur as sulfate (SO42-) using a validated method, for example, ion chromatography (APHA Method 4110).

Other decomposition methods for total sulfur analysis, for example, high temperature furnace combustion method, may be used if they can be demonstrated to be at least as rigorous as this method or validated against a CRM (Peverill et al. 2001). Examples include nitric/perchloric acid digestion (Tabatabai & Bremner 1970), sodium hypobromide digestion (Tabatabai & Bremner 1970) and sodium carbonate/sodium peroxide fusion (AOAC 1980).

9.3              Sulfate

    9.3.1         Scope and application
These methods are applicable to the determination of soluble and adsorbed inorganic sulfate in soils, sediments and other solids (AS 1289.4.2.1-1997, Rayment & Higginson 1992, ASTM C1580-09, Tabatabai