Environmental Engineering Reference
In-Depth Information
There is a wide range of indicators that can be
used to evaluate sediment quality conditions. In the
past, physical and chemical indicators have been pri-
marily used to provide a means of assessing environ-
mental quality conditions. More recently, signifi cant
effort has also been directed at the development of
biological indicators of ecosystem integrity (which
are often termed biocriteria) (OEPA 1988). These
biological indicators can apply to one or more levels
of organization and encompass many metrics,
ranging from biochemical variables to community
parameters (for example species richness). Ideally,
environmental monitoring programs would include
each of the physical, chemical, and biological vari-
ables that could, potentially, be affected by anthro-
pogenic activities. However, limitations on human
and fi nancial resources preclude this possibility. For
this reason, identifying the most relevant indicators
for assessing sediment quality conditions is
necessary.
The scoring system developed by the IJC (1991)
provides a basis for evaluating candidate indicators
relative to the intended purpose of the resultant
monitoring data (Table 7.2). Application of the
IJC (1991) criteria is dependent on identifying
the most desirable characteristics of the indicators
and subsequently evaluating the candidate indica-
tors for these characteristics. Based on the infor-
mation presented in Table 7.2, it is essential that
indicators for any monitoring purpose be sensitive,
measurable, cost-effective, supported by historical
data, non-destructive, of appropriate scale, and
non-redundant (i.e., these are the essential char-
acteristics of indicators). For sediment quality
evaluations that focus on status and trends assess-
ment, indicators that are biologically relevant,
socially relevant, interpretable, and provide conti-
nuity of measurements over time are likely to be
the most relevant (i.e., these are the important
characteristics of indicators for this monitoring
application). Application of the IJC (1991) evalu-
ation criteria facilitates the identifi cation of the
indicators that are the most relevant for assessing
sediment quality conditions. MacDonald and
Ingersoll (2000) and MacDonald
et al.
(2002a,b)
evaluated a variety of candidate indicators and
concluded that the following were particularly
relevant for assessing sediment quality conditions
in aquatic ecosystems.
Indicator of sediment quality
conditions
Receptors of interest
Sediment-dwelling
organisms
Chemistry of whole sediments
Chemistry of pore water
Toxicity of sediments to invertebrates
Structure of benthic invertebrate
communities
Wildlife resources
Toxicity of sediments to fi sh
Health of fi sh
Status of fi sh communities
Chemistry of whole sediments
Chemistry of fi sh and invertebrate
tissues
Human health
Chemistry of whole sediments
Chemistry of fi sh and invertebrate
tissues
Presence of fi sh and wildlife
consumption advisories
Again, the selection of indicators must be guided
by the sediment quality issues and concerns that are
identifi ed at the site under investigation. Where sedi-
ments are primarily contaminated by toxic sub-
stances, focusing sediment quality assessments on the
receptors that are most likely to be directly affected
by contaminated sediments is reasonable (i.e., sedi-
ment-dwelling organisms and fi sh). At sites contami-
nated by bioaccumulative substances, sediment
quality assessments need to have a broader focus,
potentially including sediment-dwelling organisms,
wildlife resources, and human health. Importantly,
the signifi cance of the decisions (i.e., size of the site,
potential clean-up costs) that may be made based on
the results of the assessment should be a central
consideration when developing a suite of indicators
for assessing contaminated sediments.
The problem formulation process provides an
effective framework for identifying the issues and
concerns that should be addressed in sediment
quality assessments (USEPA 1997, 1998). In addi-
tion to supporting identifi cation of the indicators
that should be incorporated into sediment quality
monitoring programs, the problem-formulation
process also enables investigators to select the vari-
ables that will be measured to provide the requisite
information. These variables or metrics provide the
data needed to evaluate the status of each of the
selected indicators of sediment quality conditions.
