Environmental Engineering Reference
In-Depth Information
(PTFE), pre-cleaned with a strong detergent and
rinsed with 10% HNO
3
, to minimize adsorption of
contaminants to the collection vessel and to maintain
the chemical integrity of samples containing complex
mixtures. This is not always feasible. Therefore,
depending on the aims of the survey, either appropri-
ately cleaned brown borosilicate glass with Tefl on lid
liners (organics, inorganic metals) or plastic or poly-
carbonate (inorganic metals) containers are most
commonly used. Generally, these should be fi lled to
capacity with a little 'head' space for expansion in
case of frozen storage. For anoxic sediment collection
containers should be purged with an inert gas such as
nitrogen to allow anoxic conditions to be maintained
(Ankley & Schubauerberigan 1994; Buffl ap & Allen
1995; Carr & Chapman 1995; US Environmental
Protection Agency 2001b). A vital aspect is sample
labeling, which should be clear, indelible, and reliable
even in fi eld conditions, to prevent confusion in
sample identity.
In most cases, sediments will have to be stored.
For chemical analysis, the effect of storage has been
studied on the stability of sediment-associated con-
taminants (ASTM 1990; US Environmental
Protection Agency 1992; Gomez-Ariza
et al.
1999),
their extractability (Thomson
et al.
1984), or general
sediment characteristics (Watson
et al.
1985). The
effect of storage on the toxicity of compounds is
unclear. For example, the effects of freezing ranged
from decreased toxicity in
Daphnia magna
(Malueg
et al.
1984) to no effects at all in polychaetes (Carr
et al.
1989). Accordingly, the recommended storage
periods for sediments range from 5 (Swartz 1987) or
7 days (Anderson
et al.
1987) to less than two weeks
(Shuba
et al.
1978; ASTM 1990). Therefore, storage
of sediments for prolonged periods should be
avoided. Where this is not possible, sediments should
be stored at 4 °C and storage time kept to an absolute
minimum (Luoma & Ho 1998).
Finally, health and safety regulations will vary
from country to country. However, as fi eld-collected
sediments can contain complex mixtures of poten-
tially toxic substances, including mutagens and car-
cinogens, some basic safety precautions should be
considered. It is desirable for toxicity tests to be
performed as soon as possible after collection, which
often leaves little or no time for chemical analysis
and it is therefore necessary to minimize the direct
contact of workers with sediment by using gloves,
protective clothing, and safety goggles. In extreme
cases, the presence of volatile compounds may
warrant the use of well-ventilated areas, fume hoods
or respirators (Ingersoll 1995). Special precautions
should be observed where potential radioactive sedi-
ment may be sampled (US Army Corps of Engineers
1997).
6.2.2 Test systems for sediment
toxicity assessment
The endpoints in sediment toxicity testing will vary
with the question being addressed and may include
acute and long-term toxicity, endocrine, reproduc-
tive, and genotoxic effects.
A comprehensive assessment of potential sediment
toxicity requires a tiered approach considering mul-
tiple exposure phases and test models representing
different trophic levels, levels of biological organiza-
tion, and sediment related habitats (Davoren
et al.
2005; Hartl
et al.
2005). This integrated approach
should involve the use of short-term general tests
using sediment extracts (tier 1); the application of
hazard identifi cation models, and more specifi c (mul-
tiple) endpoints in multi-organism experiments, rep-
resenting different trophic levels, habitats associated
with sediments, routes of exposure, and bioavailabil-
ity by using both sediment extracts and whole sedi-
ments (tier 2) (Hartl
et al.
2006); and the assessment
of
in situ
ecosystem function through lifetime repro-
ductive success and components of biodiversity (tier
3) (Nendza 2002).
The primary criteria for the selection of test species
include the species' ecological and/or economical
importance and their relative sensitivity to sediment
contamination, life expectancy, predictable and con-
sistent response of control organisms, ease of culture
and maintenance, reproducibility, cost, and in the
case of tiers 2 and 3 ecological relevance and expo-
sure history (Boisson
et al.
1998; Nendza 2002;
Ownby
et al.
2002).
6.2.2.1 Tier 1 tests
Although simulation of
in situ
exposure of aquatic
organisms to contaminated sediments is most realis-
tic using a whole sediment approach, this often
involves considerable infrastructural investment,
logistical considerations, animal experimentation
