Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p19
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 19/21)
Character Range: 1394717–1397805

account when deriving water quality guidelines' (ANZECC & ARMCANZ 2000). Food web approaches were not advocated because they are 'very complex and require extensive data sets, which are not available for the majority of contaminants' (ANZECC & ARMCANZ 2000). These data sets include toxicity data for top predators, biomagnification and bioaccumulation data and dietary information for the species. For terrestrial ecosystems, Australian data needed for a food web modelling approach is even scarcer. The paucity of Australian data was the main reason why a proposed food web methodology for deriving EILs was not incorporated into this guideline.

However, biomagnification algorithms are currently the best available methodology to set EILs that protect top predators if the necessary data sets are available.

3.2.9         Using a default biomagnification factor
The biomagnification default factor method refers to dividing the normal SGQ by a biomagnification factor to protect the higher predators. Predators are assumed to have the same sensitivity to the contaminant as other species, but as biomagnification occurs in the food web, the SQG is divided by a default biomagnification factor to protect the predators. This default biomagnification factor could be derived by collating biomagnification values for similar contaminants and then a specific percentile value on a log-normal basis could be adopted as the default BMF. If biomagnification values are not known, a conservative default biomagnification factor could be set (for example, 10). This is a simple and easily understood method but it could under-protect for some combinations of species and contaminants and over-protect for others. This methodology can also result in very conservative limit values.

3.2.10     Increasing the percentage of species to be protected
Increasing the percentage of species to be protected is an indirect way of addressing biomagnification and was used in the Australian and New Zealand WQGs (ANZECC & ARMCANZ 2000). For example, the level of protection was raised from 95% to 99% for slightly to moderately modified ecosystems. It is a simple method but not necessarily scientifically rigorous. As it does not directly address biomagnification, it cannot be guaranteed that the resulting limit values will provide sufficient protection. Furthermore, this methodology might give very conservative limit values which in some cases could be lower than background concentrations. This occurred when PC99 values were derived for some metals (Warne pers. comm.).

3.3              Determining ambient background concentrations

3.3.1         Inorganics
Metals and metalloids are naturally present in soils. Natural (background) concentrations of metals in soils depend on the parent rock from which the soil originated and are highly variable. Some authors (Reimann & Garrett 2005) argue that natural background concentrations no longer exist anywhere in the world due to man-made activities and global transport of contaminants. Therefore, the term ambient background concentration (ABC)