Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:20:p11
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 20 (pt 11/14)
Character Range: 1323091–1326035

taken to represent the species or process
    * if there were several toxicity values for different end points (e.g. mortality or reproduction), the end point with the lowest geometric mean was taken to represent the species or process.

SSD methods require the toxicity data to have a uni-modal distribution. If the data set is not uni-modal (for example, insecticides are more toxic to insects than mammals), then the toxicity data belonging to the most sensitive distribution should be used for ACL derivation, as recommended by Warne (1998, 2001) when deriving WQGs.

2.4.6         Normalisation of toxicity data to an Australian reference soil
The use of normalisation relationships is an attempt to minimise the effect of soil characteristics on the toxicity data so the resulting toxicity data will more closely reflect the inherent sensitivity of the test species to the contaminant. If toxicity data more closely reflects species sensitivity, then a more accurate calculation of the soil concentration that should protect a certain percentage of species and soil processes can be made. Derivation of soil-specific EILs and the use of normalisation relationships to normalise toxicity data can only be done if there is sufficient data to use the SSD method. Toxicity data should not be normalised if the available toxicity data is only sufficient to meet the minimum data requirements of the AF approach.

If the toxicity data for a contaminant has been demonstrated to be affected by soil characteristics, (that is, by statistically significant (p ≤ 0.05) normalisation relationships between toxicity data and soil characteristics), then the toxicity data must be normalised to the Australian reference soil (see Table 12 below).

Table 12. Values of soil characteristics for the Australian reference soil to be used to normalise toxicity data
Soil property  Value
pH:            6
Clay:          10%
CEC:           10                cmol/kg
Org. Carbon:   1% or equivalent OM

Normalisation relationships are currently limited to a few combinations of contaminants, species and countries from which the soils are obtained (Smolders et al. 2004; Li et al. 2003; McLaughlin et al. 2006; Song et al. 2006; Broos et al. 2007; Warne et al. 2008a; 2008b). This is predominantly due to the concept of developing normalisation equations for terrestrial ecotoxicity data being relatively recent and the size of, and cost of conducting, such work.

The lack of normalisation equations for a wide variety of species can be overcome by applying the relationships across species within the following groupings of the taxonomic groups:
    * plants, algae
    * annelids, nematode, mollusca, protozoa
    * hexapoda, myriapoda, chelicerata, tardigrada
    * microbial and fungal functional end points.
These groupings are based on the basic body design of the organisms and the likely exposure route of organisms to the contaminant; that is, being