Sediment quality standards
EQSs are only applicable in the water column and
there are no equivalent standards for sediments
used in the UK. Some operational standards for toxic
substances may be used in specific circumstances
by the environment agencies.
The approach to the development of sediment quality
standards has been summarised by Grimwood and Dixon
(1997) in the context of List II metals. The Canadian/US
approach is recommended and involves the derivation
of Threshold Effects Levels (TELs) and Probable
Effect Levels (PELs) from an extensive database
containing direct measurements of toxicity of contaminated
sediments to a range of aquatic organisms exposed
in laboratory tests and under field conditions.
Effects may be observed in some sensitive species
exposed to the TEL, whereas the PEL is likely to
cause adverse effects in a wider range of organisms.
Further information on the approach is given in
Long et al (1995). Interim sediment quality
guidelines have been adopted by Environment Canada
for a range of toxic substances (CCME 1999). The
table linked below summarises some adopted sediment
guidelines for List II metals in the Netherlands
Table - Summary of saltwater
sediment guidelines adopted for List II metals by
VROM and Environment Canada (from Grimwood and Dixon
The table linked below summarises interim marine
sediment quality guidelines issued by Environment
Canada in 1999 for a range of toxic substances.
Grimwood and Dixon (1997) stress that these guidelines
have not been validated for use in the UK and that
a proportion of the test species in the database
are not indigenous to the UK and that there may
be fundamental differences in sediment geochemistry.
However, in the absence of any UK standards,
these guidelines can be used as a first approximation
in assessing whether organisms are at risk from
sediment concentrations of toxic substances.
There are certain situations where the background
concentrations of toxic substances are higher than
normal due to human activities over many years but
where the indigenous fauna and flora have successfully
adapted to these changed conditions. For example,
metal concentrations in the Fal estuary system are
elevated due to mining activity in the catchment
and organisms have adapted to these conditions.
In general, where sediment concentrations of toxic
substances are close to or above the TEL concentration
listed in the table linked below, conservation agency
staff should identify sediment concentrations as
a cause for concern and seek to minimise further
inputs of these substances to the European marine
Table -. Interim marine sediment
quality guidelines (ISQGs) and probable effect levels
(PELs; dry weight) (from CCME 1999)