Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:6:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 6 (pt 2/5)
Character Range: 1614075–1617657

bioavailabiity of organic contaminants such as DDT. However, there were no normalisation relationships available for DDT. Therefore, the toxicity data could not be normalised to the Australian reference soil (Table 6), nor could soil-specific SQGs be derived.

6.5              Sensitivity of organisms to DDT
Figure 6 shows the SSD (that is, the cumulative distribution of the geometric means of toxicity values) for the species used to derive the DDT SQGs. There is a general paucity of terrestrial toxicity data for DDT. This is particularly the case for plants and soil invertebrates where each group only has data for two species. It is therefore difficult to assess the relative sensitivity of these groups of organisms. Soil processes had sensitivities to DDT ranging from very sensitive to very tolerant, although most were in the more tolerant part of the distribution. Both plants were tolerant of DDT. Both soil invertebrates had moderate sensitivity while the vertebrate species were generally sensitive. The greater sensitivity of the vertebrates is consistent with the findings on the relative sensitivity of aquatic species.
Table 42. The geometric mean values of the DDT toxicity data for soil invertebrate species, terrestrial vertebrate species, plant species and soil processes.
Test species          Geometric means (mg/kg)
Common name           Scientific name          NOEC or EC10  LOEC or EC30  EC50
Earthworm             Eisenia fetida           363           1131          2499
Field mustard         Brassica rapa            1000          2500          5000
Helmeted guineafowl   Numida meleagris         30            75            150
House sparrow         Passer domesticus        600           1500          3000
Japanese quail        Coturnix japonica        80            200           400
Mallard duck          Anas platyrhynchos       24            59            119
Northern bobwhite     C. virginianus           68            170           341
Oats                  A. sativa                1000          2500          5000
Ring-necked pheasant  Phasianus colchicus      104           261           522
Soil process          Ammonification           1250          3125          6250
Soil process          Nitrification            56            141           281
Soil process          Respiration              1000          2500          5000
Soil process          SIN                      1000          2500          5000
Soil process          SIR                      1000          2500          5000
Springtail            F. candida               464           1344          2836

Figure 6. The species sensitivity distribution (plotted as a cumulative frequency of the toxicity data against DDT soil concentration) of soil invertebrate species, soil processes, plant species and terrestrial vertebrate species to DDT.

6.6              Calculation of soil quality guidelines for fresh DDT contamination
All the available DDT toxicity data was reported as total concentrations without making a distinction between added and background concentrations. There was no equation available able to estimate the background concentration of DDT. DDT only occurs due to its synthesis by humans. There is therefore no natural background concentration of DDT. However, due to its persistence and its ability to volatilise, DDT can be subject to long-distance transport. In fact, a global distillation hypothesis was developed and has widely been accepted as the explanation of the presence of DDT and its metabolites and other persistent organic pollutants