Bioavalibility in Soils - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 741

contaminants with a log K ow < 6. For contaminants with a log K ow > 6 other routes,
e.g., via feeding, become more relevant for the same organisms.
16.5 Concluding Remarks
Bioavailability is an important concept when considering the ecological risks posed
by contaminated sites. Legislators are moving in the direction of incorporating
measures of bioavailability into regulations regarding contaminated sites. In par-
ticular concepts of bioavailability are important in higher tier Risk Assessments.
Whilst bioavailability, and related terms such as bioaccessibility, can be precisely
defined, the impact that soil properties have on soils and the multitude of organ-
isms found at contaminated sites means that a “one size fits all” precise definition
of bioavailability only exists on a philosophical level. Any given contaminant will
have differing bioavailabilities to different organisms in different soils. With all
this potential variability it is not surprising that a range of different methods for
measuring and calculating bioavailability exist. The chemical methods which exist
for predicting bioavailability are validated for specific conditions, but can not hope
to be universally applicable. Similarly, models have been developed which work
well for specific conditions, but are inevitably organism-specific. Thus when apply-
ing proxies for bioavailability, it is important to bear in mind the conditions for
which that proxy was developed. At present it is the case that the best method to
determine contaminant concentrations and effects in organisms is to measure them.
Chemical extractions are probably currently the better option for predicting longer
term bioavailability providing that the drawbacks of extractions are clearly stated.
However, in the future calculations will replace chemical extractions as the method
of choice for predicting bioavailability. In terms of using bioavailability measures to
support contaminated site ecological Risk Assessment and Risk Management, leg-
islators must identify key organisms, with the support of ecotoxicologists, that they
wish to protect, for example earthworms as an example of a major soil invertebrate.
Once key species have been identified there is cause to be optimistic that suitable
methods for assessing bioavailability either exist or can be developed. A key need
for legislators is not additional and new methods for measuring bioavailability, but
a series of validation studies using existing methods.
References
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Arnold RE, Hodson ME, Comber S (2007) Effect of organic complexation on the toxicity of Cu to
the earthworm Eisenia fetida . Appl Geochemi 22:2397-2405
Belfroid A, Seinen W, Van Gestel CAM, Hermens JLM, Van Leeuwen K (1995) Modelling the
accumulation of hydrophobic organic chemicals in earthworms - application of the equilibrium
partitioning theory. Environ Sci Pollut Res 1:5-15
Binger CA, Martin JP, Allen-King RM, Fowler M (1999) Variability of chlorinated-solvent
sorption associated with oxidative weathering of kerogen. J Contamin Hydrol 40:137-158