Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:8:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 8 (pt 3/5)
Character Range: 1685162–1688527

process         Denitrification                250           500           750
Soil process         Nitrification                  337           505           1010
Soil process         N-mineralisation               447           1095          1342
Soil process         Respiration                    655           982           1964
Soil process         Substrate induced respiration  1733          2600          5200
Plants
Radish               Raphanus sativus               100           500           300
Oat                  A. sativa                      100           500           300
Barley               H. vulgare                     50            250           1270
Red spruce           Picea rubens                   141           212           1228
Loblolly pine        Pinus taeda                    546           819           659
Lettuce              Latuca sativa                  125           188           174
Wheat                T. aestivum                    250           500           750
Maize                Z. mays                        100           150           300

8.4              Normalisation relationships
Only two normalisation relationships have been developed for Pb. One models the uptake of Pb by spring wheat (T. aesitivum) (Nan et al. 2002) while the other models Pb toxicity to lettuce (L. sativa) (Hamon et al. 2003). The toxicity normalisation relationship is presented below:
    EC50 = 23 pH + 171 clay content (%) - 40  (r2 = 0.84)   (equation 8)
However, while the above relationship is based on ten toxicity data sets, they were only tested in five soils. This, combined with the fact that the relationship was not validated, severely limits its applicability. The EU ecological risk assessment for Pb (LDA 2008) stated that there is no relationship between soil pH and Pb toxicity. However, it did not make any statement on whether there are relationships between Pb toxicity and other soil physicochemical properties. This was examined as part of this body of work. Relationships between the logarithm of NOEC and/or EC10 data and soil pH, log organic matter content (%), log organic carbon content (%), log clay content (%) and log cation exchange capacity (CEC) for all toxicity data combined, for plants only, for invertebrates only and for soil microbial processes only were determined (data not shown). Normalisation relationships were only derived using NOEC and EC10 data as there was considerably more of this data than LOEC and EC30 or EC50 data. Only the relationship between logarithm of Pb toxicity to plants and the logarithm of the organic carbon content was able to explain more than 50% of the variation in toxicity data (r2 = 0.56).

Normalisation relationships that explain such a low percentage of the variation (that is, <60%) are not usually used to normalise toxicity data as they do not account for enough of the variability caused by the soil (Warne et al. 2008b). The majority of the relationships derived explained less than 10% of the variation in toxicity data and only three could explain more than 10%. Thus there are no useful normalisation relationships available for Pb, so the toxicity data was not normalised to the Australian reference soil, nor were soil-specific SQGs derived.

8.5              Sensitivity of organisms to lead
The SSD for the Pb NOEC toxicity data is