Environmental Engineering Reference
In-Depth Information
can often not be replicated accurately under labora-
tory conditions.
In situ
studies, on the other hand,
allow not only the observation of the effects of
chronic (often multi- generation) exposure to con-
taminated sediments, but will also provide more real-
istic information concerning contaminant fate.
Relevant examples of
in situ
tests can be found in
Table 6.8.
In situ
effects assessments can be described as envi-
ronmental measurements made in the fi eld with
limited manipulation and disturbance of the sedi-
ment physico-chemical gradients and associated
microhabitats. Therefore mitigation of handling and
laboratory-induced artifacts is likely to give a more
accurate representation of biotic and abiotic factors
that are likely to affect routes of exposure and inter-
actions with sediment-associated organisms, either a
single species, populations, or communities; the last
of these will depend to a certain extent on commu-
nity structure. Contaminant exposure will manifest
itself in various direct and indirect ways: direct
effects include changes to distribution and abun-
dance of taxa in proportion to their sensitivity; indi-
rect effects can arise from changes to fecundity and
alterations to food-web structure. Therefore changes
to benthic community structure can be used to assess
sediment quality.
Although understanding the fate of contaminants
in the fi eld is of great signifi cance in environmental
impact assessments, there are several problems and
constraints with
in situ
contaminant effect studies.
Most notable are the sophisticated and often costly
logistics involved in identifying suitable study (and
control) sites, the collection and deposition (in the
case of organism transfer experiments) of indicator
species, and the complexity of data interpretation.
Chronic studies often require the monitoring (and
repeated observation) of individual animals, which
Table 6.8
Examples of fi eld studies using a variety of taxa.
Taxa
Species
Enlosure
In situ
Contaminants
Biomarker
Reference
Polychaetes
Hediste diversicolor
Acrylic
tubes
+
Metals
Behaviour; AChE;
LDH; GST; SOD
Moreira
et al.
(2006)
Molluscs
Elliptio complanata
−
+
PAHs
DNAdamage
Humphries (2006)
Mytilus galloprovincialis
Caged
+
Metals
DNAdamage; GST
Regoli
et al.
(2004)
Ruditapes philippinarum
Caged
+
PAHs, PCBs,
metals
EROD; MTLP;
GST; GPX
Martin-Diaz
et al.
(2008)
Crustaceans
Hyalella azteca
Chambers
+
Metals
Survival
Robertson & Liber (2007)
Carcinus maenas
Caged
+
PAHs, PCBs,
metals
EROD; MTLP;
GST; GPX
Martin-Diaz
et al.
(2008)
Insects
Chironomus riparius
PVC tubes
+
PM; lindane
AChE
Maycock
et al.
(2003)
Invertebrate communities
Invertebrate communities
+
Metals
Community
structure
−
Fish
Gobius niger
−
+
PAHs
EROD
Ramsak
et al.
(2007)
Ameiurus nebulosus
−
+
PAHs, PCBs,
DDT
HIS
Yang & Baumann (2006)
Micropterus salmoides
−
+
PAHs
EROD, ALAD,
GST, SULT, UGT
Schreiber
et al.
(2006)
Parophrys vetulus
−
+
PAHs, PCBs,
AHs, Dioxins
CYP1A,
histopathology,
DNA damage
Malinsetal
et al.
(2004)
Gillichthys mirabilis
Caged
+
PAHs, PCBS,
DDT, Metals
Growth
Forrester
et al.
(2003)
