Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 3/21)
Character Range: 1352551–1355606

measurements were not useful predictors of plant and microbial toxicity in soils and thus used total metal concentrations to develop normalisation relationships. In contrast, a number of other studies have reported various extractable measures to be better than total concentrations ( Posthuma & Notenboom 1996; Vijver et al. 2001; Nolan et al. 2005; Menzies et al. 2007).

McLaughlin et al. (2010) in a review of how to derive soil standards for trace elements concluded 'it is difficult to conclude that one particular extractant or type of extractant is superior to others in predicting the trace element bioaccumulation and toxicity across a range of soils or organism endpoints'. There is also considerably more toxicity data expressed as total metal concentration. A further issue to be considered in development of EILs using extractable concentrations of contaminants would be the significant analytical challenge for many laboratories to consistently extract and accurately determine the low concentrations of contaminants found in partial extracts of soil.

One disadvantage of using total contaminant concentrations instead of a partial extract of soil designed to measure bioavailability is that different sources of contamination, having differing bioavailability, are not differentiated. However, for a screening level risk assessment such as the use of EILs, use of total concentrations is protective.

For the purposes of developing EILs (which are used across soils with a wide range of properties), there is some evidence from both overseas and Australia that, at least for metals, extractable concentrations in soil may not necessarily be better measures of bioavailability than total concentrations.

3.1.2         Normalisation relationships
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. If toxicity data more closely reflects species sensitivity, then a more accurate estimate of the soil concentration that should protect a certain percentage of species and soil processes can be derived. Normalisation relationships are also used to extrapolate ACL values determined for the Australian reference soil out to soils with a range of physicochemical properties (that is, different soils). To normalise toxicity data, empirical relationships are needed between soil characteristics and toxicity data. An example of a relationship between toxicity and a soil property is given in Figure 3, which shows how toxicity values increase with increasing soil pH.

Normalisation relationships are relatively simple empirical relationships between the toxicity or plant uptake data for a single contaminant to one species and the physicochemical properties of the soils where the tests were conducted. These empirical relationships are usually obtained using data from laboratory studies in which a single species is exposed to a single contaminant in different soils.