Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:20:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 20 (pt 2/2)
Character Range: 1536149–1538267

of soil quality guidelines based on protecting aquatic ecosystems from leaching of fresh zinc contamination
As indicated in the exposure pathway assessment, the log Kd values for Zn measured in a range of Australian soils were below 3 and therefore there is the potential in some soils for Zn to leach to groundwater and effect aquatic ecosystems. Although the calculation of SQGs based on protecting aquatic ecosystems from the effects of leached contaminants is not included in the EIL derivation methodology (Schedule B5b), the calculations are presented here to illustrate the recommended approach and what effect this has on the resulting SQGs. The following SQGs were based on the ACL(NOEC & EC10) values for urban residential/public open space land use.

The soil-specific SQGs for Zn that accounted for leaching potential were calculated using the US EPA method (US EPA 1996).

    SQG = Cw . (Kd + (θw + θa . H) / ρb) . DAF    (equation 2)

where SQG is the appropriate soil quality guideline in soil (mg/kg), Cw is the target soil leachate concentration (mg/L) (that is, the Australian and New Zealand freshwater quality guideline for Zn, (ANZECC and ARMCANZ 2000)), Kd is the soil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[2]. The values of DAF used in the calculations were 1 and 20. There is a linear relationship between the DAF and the SQGs, thus the SQGs calculated using a DAF of 20 are 20 times larger than those calculated using a DAF of 1.

The value for θw was set to 0.1 Lwater/Lsoil, θa was set to 0.1 Lair/Lsoil and ρb was set to 1.3 kg/L. The calculated SQG values when DAF was 1 and 20 are presented in Tables 15 and 16 respectively.
Table 15. Soil-specific zinc (Zn) soil quality guidelines (SQG(NOEC & EC10), mg total Zn/kg) based on protecting groundwater ecosystems from groundwater leaching when the dilution and attenuation factor (DAF) was 1.
pH  CEC (cmolc/kg)