Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 1/21)
Character Range: 1347059–1350146

3                   Technical notes on methods used in the EIL derivation methodology
In this section, the various methods used in the EIL derivation methodology are more thoroughly explained and their strengths and limitations discussed. Recommendations on which methods should be used are also provided. The methods addressed in this section are:
    * to account for the effect that soil characteristics have on toxicity and bioavailability
    * for calculating ACLs
    * for measuring and incorporating ABCs
    * to account for bioaccumulation and secondary poisoning effects.

3.1              Methods to account for the effect of soil characteristics on toxicity and bioavailability
Soil characteristics are known to affect bioavailability and therefore the toxicity of contaminants to organisms (Lexmond 1980; McBride 1989; Alloway 1995; Basta et al. 2005). An example of the strong effects that soil characteristics have on toxicity is provided in Table 17. This shows laboratory-based toxicity data (EC10) for Cu and Zn to wheat grown in 14 different Australian soils (Warne et al. 2008a). The lowest and highest EC10 values vary 20–30 fold for both Cu and Zn. As the conditions were standardised and only one test species was used, the cause for the differences in toxicity can only be soil type and soil properties.
Table 17. Total added concentrations (mg metal/kg soil) of Cu and Zn that cause a 10% reduction in growth for wheat seedlings (EC10) grown in 14 Australian soils (Warne et al. 2008a)
Site           Cu EC10  Zn EC10
Avon           945      755
Brennans       205      275
Bundaberg      260      235
Cecil Plains   3,300    5,855
Dalby          885      655
Dookie         490      965
Dutson Downs   -        875
Esk            465      565
Flat Paddock   115      250
Kingaroy       810      505
Night Paddock  110      530
Spalding       930      620
Tintinara      430      430
Wilsons        465      335

There are two methods that attempt to address the issue of the effects of soil characteristics. These are to express toxicity data in terms of a contaminant estimate of the bioavailable fraction of a contaminant and to express toxicity data in terms of total concentrations and develop relationships (termed normalisation relationships) between toxicity and soil characteristics that account for bioavailability (see McLaughlin et al. 2000a for a discussion of these two philosophies).

3.1.1         Chemical estimates of bioavailability
A number of soil extraction methods have been developed with the aim of providing a better estimate of the bioavailable fraction than total concentrations. These include calcium chloride (CaCl2) extracts, ammonium nitrate (NH4NO3) extracts, soil solution and other extracts and diffusion-based methods (for a review, see McLaughlin et al. 2000b). The extraction methods assume that they only extract that portion of the total amount of a chemical that is biologically available. This is a chemical approach to estimating the bioavailable fraction.

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