Environmental Engineering Reference
In-Depth Information
In addition to the substances that are expected to
partition into sediments (owing to their physical-
chemical properties), it may be appropriate to include
additional COPCs that are likely to partition prima-
rily into water. It is necessary to include several vari-
ables (e.g., pH, water temperature, water hardness,
dissolved oxygen) that will provide ancillary infor-
mation for interpreting the data on the primary
chemical metrics.
Sediment chemistry data provide information that
is directly relevant for determining if sediments
within an assessment area are contaminated with
toxic and/or bioaccumulative substances. However,
information on the concentrations of contaminants
in whole sediments (i.e., the metrics for sediment
chemistry) does not, by itself, provide a basis for
determining if the ecosystem goals and objectives are
being achieved. For this reason, it is necessary to
establish sediment quality targets for sediment chem-
istry that defi ne the levels of each metric (i.e., the
COPCs and mixtures of COPCs) that are likely to
support the designated uses of the aquatic ecosystem
(i.e., the benthic invertebrate community). These
targets can be established by selecting appropriate
SQGs for each COPC at the site. Such SQGs can be
derived using information on contemporary back-
ground levels and/or on the concentrations associated
with a pre-selected probability of observing adverse
biological effects (see, for example, MacDonald
et al.
2000b; Field
et al.
2002). The recommended proce-
dures for assessing sediment chemistry data are sum-
marized in Fig. 7.1 and Table 7.3.
Assemble sediment chemistry
data
DQOs not
met
Evaluate sediment chemistry data
using data quality objectives in
quality assurance project plan
Repeat necessary
components of sampling and
analysis plan
DQOs met
≤
BKGD
Sediments unlikely to be
contaminated beyond
background levels
Compare sediment chemistry
data to background levels
> BKGD
< SQGs
Compare sediment chemistry
data to sediment qualtiy
guidelines
Sediments unlikely to be
contaminated to hazardous
levels
> SQGs
Sediments contain elevated
and potentially hazardous
levels of contaminants
Consider sediment chemistry
data with data on other
indicators
Fig. 7.1
Recommended procedure for
assessing sediment chemistry data.
