Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p8
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 8/10)
Character Range: 1460969–1463994

low potential to leach. Conversely, contaminants with a low log Kow tend to have a high potential to leach. Log Kow and log Koc have a linear relationship (Briggs 1981, Connell 1989).
log Koc = 0.9 x log Kow + 0.62              (equation B1)

Therefore log Kow (which is much more readily available than log Koc) can act as a surrogate of the potential for contaminants to leach from soil to groundwater. On this basis, Wilson et al. (1996) used log Koc and log Kow to classify the mobility of organic contaminants in soil (Table B2).
Table B2. The classification system used for the mobility of organic contaminants in soil based on the logarithm of the organic carbonwater partition coefficient (log Koc) and logarithm of the octanolwater partition coefficient (log Kow). Modified from Wilson et al. 1996.
  Corresponding      log Koc      Classification of mobility
  log Kow values1
  <2                 <2.4         Mobile (M)
  2.02.7            2.43.05     Medium mobility (MM)
  2.73.7            3.053.95    Low mobility (LM)
  >3.7               >3.95        Immobile (IMM)

1. log Kow values corresponding to the log Koc values were derived using equation B1.
Many organic contaminants can degrade either biologically or chemically. Thus, it is recommended that EILs derived for organic contaminants with a slow degradation rate (that is, large half-life, refer to Table 2) and a log Koc (or log Kow) <4 should consider the protection of aquatic ecosystems where appropriate.

5.2.3         Calculation of EILs that protect aquatic ecosystems
The US EPA methodology (US EPA 1996) may be used to calculate EILs that account for the potential of contaminants to leach and affect aquatic ecosystems. Although the method has its limitations due to several simplifications, it is a robust method where the required information is available for Australian soils.

5.2.3.1         Inorganic contaminants
The potential leaching of inorganic contaminants to the groundwater depends on the soil to water partitioning of the contaminant, Kd, which is contaminant- and soil-dependent. Furthermore, volatilisation can reduce the soil concentration of the inorganic contaminant and this amount will reduce the potential of the contaminant to leach to the groundwater. For essentially all inorganic contaminants, volatilisation is limited; however, for Hg, a substantial amount can be volatilised.

Because groundwater catchments will most likely contain both contaminated and uncontaminated soils, pore water concentrations of the contaminant in question will not always equal the groundwater concentration. Therefore, a dilution and attenuation factor (DAF) is used to take this into account. The fraction of contaminated land to the total area of the local groundwater/aquifer 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):