Environmental Engineering Reference
In-Depth Information
Figure 9.4. Biological and ecological
assessment.
the receptor. Furthermore, it has been established that the contaminant is
present at concentrations that may cause harm to the receptor. At Tier 2,
detailed assessment of the effects (or potential effects) of contaminant exposure
on the receptor is made, using bioassays, ecological surveys or both ( Fig. 9.4 ). The
outcome of a Tier 2 assessment is whether the risk assessor can confidently
identify that significant harm (SH) or SPOSH is occurring to the ecological
receptor(s).
Bioassays
Following an extensive road-testing exercise, where a number of bioassays of
potential use for determining effects in industrial soils were trialled at real
sites, the Environment Agency presently endorses ten biological tests for use at
Tier 2 of the ERA (Environment Agency 2004b , c , 2008d , e ). The tests and their
potential application are presented in Table 9.2 .
Although the bait lamina test can be used in situ, the majority of tests must
be performed under controlled laboratory tests. This can be done by taking soil
samples collected from the site under investigation for use in the laboratory.
The choice of which test(s) to use will be informed by the desk study and
CSM. Where the receptor of concern is a plant, a combination of soil function-
ing and plant biology tests will probably be used (e.g., bait lamina/nitrogen
mineralisation and seedling emergence, growth and vegetative vigour). In
contrast, if the receptor of interest is an invertebrate a combination of soil
functioning and invertebrate tests will probably be used (e.g., bait lamina and
earthworm or collembolan tests). Food chain effects can also be considered, so
that invertebrate tests can be used (with caution) to determine likely effects of
contaminants on insectivorous animals (similarly, plant tests can be used (with
caution) to determine effects on herbivorous receptors). For birds and other
higher organisms, biological tests are likely to be too far removed from natural
processes to be of use; in such circumstances ecological surveys are the pre-
ferred measure of SH or SPOSH.
Although some of these tests may be used as surrogates for other species
(e.g., for birds), there may be receptors where bioassays are not appropriate,
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