Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 5/21)
Character Range: 1358122–1360956

Zn = 0.55*pH – 0.55   R2 = 0.74 (equation 9)
Plant (toxicity)
log EC10  Zn  = 0.271 * pH + 0.702 * log CEC adj.  R2 = 0.66  (equation 10)

where pH is the soil pH (0.01 M CaCl2), CEC is the cation exchange capacity, EC10 is the concentration that causes  a 10% effect.

Normalisation relationships are currently limited to a few combinations of contaminants, species and countries from which the soils are obtained. The lack of normalisation equations for a wide variety of species can be overcome by applying the relationships to species other than those for which they were derived (EU 2006b). However, this practice should only be conducted if it could be expected that the contaminant would exert its toxicity in the same manner as to the other species and the application of the normalisation relationship leads to a decrease in the range of toxicity values for the other species (EU 2006b).

The lack of normalisation equations for Australian soils can be overcome by using relationships developed with soils from other countries, particularly Europe and America. However, these normalisation relationships should only be used when they are derived from soils similar to Australian soils and/or if their validity for Australian soils has been assessed and found suitable[6]. The importance of this was shown by a study of Broos et al. (2007). This study assessed the normalisation relationships of Smolders et al. (2004) and Oorts et al. (2006) and re-analysed the data after removing microbial toxicity data for soils with OC concentrations greater than those found in Australian soils. This resulted in a change of soil characteristics, mainly explaining the variance in the toxicity data. For the initial data set, OC was the most important factor explaining the toxicity of Zn and Cu to nitrifying microorganisms but without the high OC soils, pH became the main explanatory soil property.

Normalisation relationships usually take the form of:
Toxicity data = a * soil property ± b              (equation 11)

where a is the gradient of the regression and b is the y-intercept. The y-intercept is a measure of the inherent sensitivity of the test species used to derive the normalisation relationship—and each species will have a unique y-intercept. Thus, when applying normalisation relationships to other species, the toxicity data should only be transformed using the gradient (that is, a in equation 11) of the normalisation relationship (EU 2006).

A second option to overcome the lack of normalisation relationships in the 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