Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p6
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 6/21)
Character Range: 1360662–1363649

literature is to examine the currently available toxicity data, and use regression analyses on the collated data to determine if a significant relationship exists between toxicity thresholds and soil characteristics.

Normalisation relationships from field studies are preferred over those from laboratory studies. All the normalisation relationships for toxicity apart from those developed by Broos et al. (2007) and Warne et al. (2008b) model laboratory-based data (Rooney et al. 2006; Smolders et al. 2003; Smolders et al. 2004; Oorts et al. 2006; EU 2006; Song et al. 2006; Warne et al. 2008a). Warne et al. (2008b) found that field-based normalisation relationships gave much more accurate estimates of field phytotoxicity than laboratory-based normalisation equations. Therefore, field-based normalisation relationships should be used to model field-based phytotoxicity data in preference to laboratory-based normalisation relationships. It is, however, realised that the current lack of the field-based normalisation relationships will unavoidably necessitate the use of laboratory-based relationships, despite their limitations.

3.1.3         Normalisation of toxicity data to a reference soil
If there are normalisation relationships for a toxicant, then the toxicity data should be normalised to a reference soil with a specified set of soil characteristics before the data is used in the SSD to derive the ACL value. Therefore, a reference soil for Australia should be used to normalise all the toxicity data (see Table 12). The specific setting of the Australian reference soil does not affect the EILs; however, all data should be normalised to the same chosen setting. Furthermore, it does not matter if all data is normalised to different settings and then an ACL value is calculated using the SSD method, or if one Australian setting is used, an ACL value is calculated and then the normalisation equation is used to calculate ACLs for different soil settings. This is because of the statistical methodology behind the SSD and normalisation approach.

Figure 4 shows how normalisation of toxicity data leads to a significant decrease in variation in toxicity values for a species (from the blue to the purple points in the figure). Therefore, the normalised toxicity data more accurately reflects the inherent sensitivity of each species.
Figure 4. Example of the effect of normalising using microbial toxicity data from the National Biosolids Research Program. The red arrows show how each toxicity value was normalised. The blue and pink arrows show the variation in toxicity values for the non-normalised and normalised data respectively. In this case the toxicity data was normalised to a pH of 6.

3.2              Methods to calculate soil quality guidelines
In general, there are three main methods to derive SQGs. These are in order of increasing complexity: the geometric mean method, AF methods and SSD methods. They are discussed below.

3.2.1         Species