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7. Developing Site-Specific Water Quality Criteria
surements for water, sediments, benthic invertebrates, and fish and
aquatic bird tissues. There is no minimum number of measurements,
but spatially complete sampling efforts will ensure that the range of
habitat types and environmental conditions present are included in
the assessment, and that inclusion of the full range results in a criterion which accurately reflects local selenium cycling and aquatic ecology. Moreover, criteria generated from robust data sets will be considered
more credible by regulatory agencies that must approve their implementation (eg, USEPA) than criteria based on just a few measurements.
Refer to Chapter 4 for details on sampling procedures.
It is important to designate a Hydrological Unit (HU) as the physical
area to be examined in the criterion review process. The hydrological
pathways that transport selenium across the landscape have important
implications for setting water quality criteria for this environmental
contaminant. For example, a criterion that is appropriate for a stream
or river where low bioaccumulation occurs may result in seemingly
harmless concentrations of waterborne selenium becoming a problem
in downstream reservoirs or in off-channel bays and wetlands where
bioaccumulation is greater. In order to develop environmentally sound
criteria, hazards to down-gradient aquatic habitats, most of which may
fall outside of what would typically be considered the "site", must be
assessed and accounted for. The HU technique is the only method that
does this effectively. Failure to use a HU approach can result in significant biological and legal problems. Consult Chapter 6 for information
on the rationale and justification for using HUs in the criterion derivation process and for details on how to delineate HUs.
Reproductive assessment (teratogenic deformities and embryo/larval mortality) should be conducted on at least one selenium-sensitive
species of fish and aquatic bird that resides in the HU: a centrarchid or
salmonid fish (eg, genus Lepomis, Micropterus, Oncorhynchus, Salvelinus),
a duck (eg, genus Anas), or a wading bird (eg, genus Recurvirostra) for
example. The basic procedure is to collect larval fish using ichthyoplankton sampling techniques, to randomly select eggs from aquatic
bird nests, and to examine both for terata or embryo mortality. Consult
Chapter 5, and Skorupa and Ohlendorf (1991) for details on methods
to evaluate impacts of selenium on reproductive success. Guidance for
measuring selenium residues, interpreting tissue concentrations, and
making comparisons to biological-effects thresholds is available in Table
7.1 and Chapter 2.
Several outcomes and conclusions are possible from the assessment
in Step 1. The criterion may be appropriate as it is, or it may be inappropriate and need to be raised or lowered. If the empirical evidence
indicates that a revised criterion is necessary (guided by the decision
tree), the investigator should proceed with Step 2.
7. Developing Site-Specific Water Quality Criteria
surements for water, sediments, benthic invertebrates, and fish and
aquatic bird tissues. There is no minimum number of measurements,
but spatially complete sampling efforts will ensure that the range of
habitat types and environmental conditions present are included in
the assessment, and that inclusion of the full range results in a criterion which accurately reflects local selenium cycling and aquatic ecology. Moreover, criteria generated from robust data sets will be considered
more credible by regulatory agencies that must approve their implementation (eg, USEPA) than criteria based on just a few measurements.
Refer to Chapter 4 for details on sampling procedures.
It is important to designate a Hydrological Unit (HU) as the physical
area to be examined in the criterion review process. The hydrological
pathways that transport selenium across the landscape have important
implications for setting water quality criteria for this environmental
contaminant. For example, a criterion that is appropriate for a stream
or river where low bioaccumulation occurs may result in seemingly
harmless concentrations of waterborne selenium becoming a problem
in downstream reservoirs or in off-channel bays and wetlands where
bioaccumulation is greater. In order to develop environmentally sound
criteria, hazards to down-gradient aquatic habitats, most of which may
fall outside of what would typically be considered the "site", must be
assessed and accounted for. The HU technique is the only method that
does this effectively. Failure to use a HU approach can result in significant biological and legal problems. Consult Chapter 6 for information
on the rationale and justification for using HUs in the criterion derivation process and for details on how to delineate HUs.
Reproductive assessment (teratogenic deformities and embryo/larval mortality) should be conducted on at least one selenium-sensitive
species of fish and aquatic bird that resides in the HU: a centrarchid or
salmonid fish (eg, genus Lepomis, Micropterus, Oncorhynchus, Salvelinus),
a duck (eg, genus Anas), or a wading bird (eg, genus Recurvirostra) for
example. The basic procedure is to collect larval fish using ichthyoplankton sampling techniques, to randomly select eggs from aquatic
bird nests, and to examine both for terata or embryo mortality. Consult
Chapter 5, and Skorupa and Ohlendorf (1991) for details on methods
to evaluate impacts of selenium on reproductive success. Guidance for
measuring selenium residues, interpreting tissue concentrations, and
making comparisons to biological-effects thresholds is available in Table
7.1 and Chapter 2.
Several outcomes and conclusions are possible from the assessment
in Step 1. The criterion may be appropriate as it is, or it may be inappropriate and need to be raised or lowered. If the empirical evidence
indicates that a revised criterion is necessary (guided by the decision
tree), the investigator should proceed with Step 2.