Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:11:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 11 (pt 1/6)
Character Range: 1770180–1773091

11             Summary
The methodology for deriving SQGs, detailed in Schedule B5b, was implemented to calculate SQGs based on different types of toxicity data for eight contaminants (arsenic, chromium, copper, DDT, lead, naphthalene, nickel, zinc). These eight chemicals were selected as they have a variety of physicochemical properties and, as a result, would behave differently in the environment. They are frequently found in urban Australian contaminated sites. The results of this process are summarised below for each contaminant. Some contaminants have the potential to leach from the contaminated site and thus may cause deleterious effects on groundwater and surface water ecosystems. The fact that contaminants can leach can be taken into account in deriving SQGs. This was done for zinc and arsenic, to illustrate the process and to illustrate the effect that it can have on the resulting SQG.

There was a considerable amount of toxicity data available for the essential element zinc. Zinc does not biomagnify but has the potential to leach from contaminated soil to groundwater. The minimum data requirements to use the SSD method were exceeded, there were multiple normalisation relationships, and there was an ageing/leaching factor. The toxicity data could be expressed in terms of added Zn concentrations; therefore, high reliability soil-specific Zn ACL(NOEC & EC10), ACL(LOEC & EC30) and ACL(EC50) values and corresponding SQG values could be derived for:
    * fresh contamination
    * aged contamination
    * protection of aquatic ecosystems
    * areas of ecological significance, urban residential/public open space, and commercial/industrial land uses.
Soil-specific ACLs could be derived, so a suite of values were generated. For example, the ACL(NOEC & EC10) values for urban residential/public open space sites freshly contaminated with Zn ranged from 20 (at a cation exchange capacity of 5 and a soil pH of 4) to 330 mg/kg (at a cation exchange capacity of 60 and a soil pH of 7.5). The range of ACL values reflects the ability of different soils to modify the bioavailability and toxicity of Zn. Correcting for ageing led to a marked increase in the ACL values. The corresponding ACL(NOEC & EC10) values for aged Zn contamination range from 45800 mg/kg. As such, correcting for the ageing of Zn led to a more than doubling of the recommended ACL values. The ACL(LOEC & EC30) and ACL(EC50) values were approximately 1.252 and 1.52 times larger, respectively, than the corresponding ACL(NOEC & EC10) values. The lowest of the Zn ACLs for urban residential land/public open space (20 mg/kg) are essentially identical to the lowest corresponding international SQGs, while the higher Zn ACLs are considerably larger than any international SQG.

Arsenic does not biomagnify in oxidised soils but has the potential to leach from contaminated soil to groundwater. Therefore, only the