Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p9
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 9/10)
Character Range: 1463751–1466713

catchment can be used to calculate the DAF, as indicated by equation B1 below.

DAF = 100 ÷ percentage of contaminated soil in local catchment (equation B2)

Therefore, for inorganic contaminants the EIL is calculated as follows (US EPA 1996):

           (equation B3)
where EIL is the ecological investigation level in soil (mg/kg), Cw is the target soil leachate concentration (mg/L) (that is, the appropriate WQG), Kd is the soil to water partition coefficient (L/kg), θw is the water-filled soil porosity Lwater/Lsoil), θa is the air-filled soil porosity (Lair/Lsoil), ρb is the dry soil bulk density (kg/L), H is the Henry's law constant (unitless), and DAF is the dilution and attenuation factor.

5.2.3.2         Organic contaminants
Organic contaminants can bind to the organic carbon in soil. The extent of this depends on the properties of the contaminant and the amount and type of organic carbon in the soil. For organic contaminants the equation for soil to groundwater migration becomes (US EPA 1996):
           (equation B4)
where EIL is the ecological investigation level in soil (mg/kg), Cw is the target soil leachate concentration (mg/L) (that is, the appropriate WQG), Koc is the organic carbon to water partition coefficient (L/kg), foc is the organic carbon content of soil (kg/kg), θw is the water-filled soil porosity (Lwater/Lsoil), θa is the air-filled soil porosity (Lair/Lsoil), ρb is the dry soil bulk density (kg/L), H is the Henry's law constant (unitless), and DAF is the dilution and attenuation factor that is calculated as per equation B2.

The target soil leachate concentration (Cw) should be set as the relevant WQG for that contaminant in groundwater systems, which currently is the surface freshwater TV (ANZECC & ARMCANZ 2000).

5.3              Appendix C: Methods for determining the bioavailability of contaminants and how this could be incorporated into the ERA framework
The methodology for deriving EILs outlined in this Schedule accounts for the effects of soil reactions that modify the bioavailability of soluble contaminants. However, it does not take into account the form or bioavailability of the contaminant. The EIL derivation framework also makes the assumption that ecotoxicity data in the literature is derived using highly bioavailable forms of contaminants (for example, soluble metal salts or soluble organic molecules), and indeed this is generally the case for most ecotoxicity studies. Thus, the framework is reasonably conservative in its assumptions and protective, and is appropriate for a screening level risk assessment.

Soil contamination can occur from a variety of sources, and not all these sources have 100% bioavailability when they are initially added to soil; for example, vitreous slags, tyre debris, massive metal, encapsulated materials, etc.

When total concentrations of contaminants are determined in a soil containing these materials, these contaminants will be solubilised,