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7. Developing Site-Specific Water Quality Criteria
Examples of Criterion Derivation
Example 1: Lowering a Criterion
The existing criterion is 5 Ilg SelL, and the following information is
available for the HU (Ilg Selg concentrations are in dry weight):
Waterborne concentrations of selenium are 1-3 Ilg/L.
Concentrations of selenium in sediments are 2-4 Ilg/g.
Concentrations of selenium in aquatic food-chain organisms are 1-7 Ilg/g.
Concentrations of selenium in randomly sampled aquatic-bird eggs
are 4-12 Ilg/g.
Teratogenic deformities occurred in 2 % of randomly sampled aquaticbird eggs.
Embryomortality occurred in 4 % of randomly sampled aquatic-bird
eggs.
Concentrations of selenium in whole-body samples of fish are 6-10
Ilg/ g.
Teratogenic deformities occurred in 5 % of fish from ichthyoplankton
samples.
Concentrations of selenium in ichthyoplankton samples are 8-12
Ilg/ g.
Evaluation: The residues present in the HU span the toxic threshold
ranges (some are below, some are within, and some are above), and
reproductive effects are occurring.
Conclusion: These conditions warrrant a 50% (2.5 Ilg SelL) reduction
in the criterion. The final criterion for chronic exposure is set at 2.5 Ilg
SelL.
Example 2: Raising a Criterion
The existing criterion is 5 Ilg SelL, and the following information is
available for the HU (Ilg Se/g concentrations are in dry weight):
Waterborne concentrations of selenium are 5-12 Ilg/L.
Concentrations of selenium in sediments are <1 Ilg/g.
Concentrations of selenium in aquatic food-chain organisms are <2 Ilg/g.
Concentrations of selenium in randomly sampled aquatic-bird eggs
are <3 Ilg/g.
Teratogenic deformities occurred in 0% of randomly sampled aquaticbird eggs.