Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p6
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 6/15)
Character Range: 1265826–1268894

Several of the physicochemical properties shown are soil-dependent, for example, soil pH, cation exchange capacity, organic matter, clay content and dissolved organic carbon.

However, others are physicochemical properties of the contaminant itself, for example, partitioning between octanol and water (Kow), its soil to water partition coefficient (Kd), Henry's law constant (H). These physicochemical properties can be used to determine the most important exposure pathways for contaminants. Organic and inorganic contaminants have different physicochemical properties that control their environmental fate and therefore different schemes for assessing exposure routes have been developed.

The EIL derivation methodology aims to protect soil and terrestrial species and soil processes. Potential off-site migration and its potential impacts are not included in the methodology. A recommended method for deriving EILs and/or other SQGs that also protects aquatic ecosystems is presented as an Appendix. Another issue that was considered for incorporation into the EIL derivation methodology was the bioavailability of the contaminants before addition to soil; for example, soluble contaminants versus those bound in insoluble forms. While this is a central issue in the management of contamination, it is not currently possible to incorporate this into the derivation of EILs and/or SQGs and the derivation assumes contaminants are 100% bioavailable. Some information on potential methods for assessing bioavailability and how it could be incorporated into a more detailed site-specific risk assessment is provided as an Appendix.

Box 1. Overview of potential exposure pathways in terrestrial ecosystems
Exposure pathways

    1. Soil – organism (via ingestion, organisms include herbivores and soil dwellers)

    2. Soil – soil organism (passive absorption)

    3. Soil – soil organisms – soil predators

    4. Soil – plants

    5. Soil – surface water – aquatic organisms

    6. Soil – groundwater – stygofauna

    7. Soil – groundwater – surface water – aquatic organisms

    8. Soil – groundwater – sediment – mieofauna

    9. Soil – air – terrestrial species

  10. Soil – plant – herbivores – carnivores

  11. Soil – soil organisms  and/or soil predators – terrestrial predators

  12. Soil – groundwater – surface water – aquatic organisms – aquatic predators

The exposure pathways can be grouped together:
    * The direct toxicity pathways are 1, 2 and 4 and should be addressed for all contaminants.
    * Leaching pathways include pathways 6, 7 and 8 and are relevant for site-specific ecological risk assessment. It will not be considered for general EIL derivation.
    * Secondary poisoning includes pathways 3, 10, 11 and 12 and should be addressed for contaminants having biomagnification potential in the food web.
    * A site-specific pathway for sloping land is pathway 5 and this should be assessed for contamination situated on slopes where down-slope migration of the contamination is possible. It will not be considered for general