Coastal Marine Environment Sustainability - Sustainable Practices in Geoenvironmental Engineering - page 269

dioxins, tributyltins (TBT), heavy metals, etc., in living organisms such as seaweed, sea
turtles, shellish, ish, etc. (Jensen et al., 2004; Gardner et al., 2003; Green and Knutzen,
2003). In some coastal areas and bays near urban centers, studies show that the sediments
are heavily polluted with heavy metals and other hazardous substances (Jones and Turki,
1997; Kan-Atireklap et al., 1997; Fukue et al., 1999; Ohtsubo, 1999; Cobelo-García and Prego,
2003; Romano et al., 2004; Selvaraj et al., 2004). Makiya (1997) reports an intake of dioxins
in the range of 60% to 70% from a one day ingestion of ish and shellish. To eliminate the
root of the human food chain problem requires one to decontaminate the contaminated
sediments. This will eliminate the food source for the lower trophic levels. Until such is
achieved, the danger of ingesting ish and shellish that have bioaccumulated toxic and
hazardous substances will always be present.
8.2.5.1 Some Case Studies of Sediment Contamination
Evidence of sediment contamination from land-based anthropogenic activities can be found
in both marine coastal regions and also at the bottom of rivers, lakes, and other bodies of
receiving waters. At a site in Germany, a lignite seam was found to accumulate aliphatic
and aromatic chlorinated hydrocarbons downstream from a chemical plant (Dermietzel
and Christoph, 2002). An initial fast desorption occurred from the outer surface of the sedi-
ment, followed by a slower diffusion-controlled released from the interior of the sediment.
Sediment samples from Lake Harwell, South Carolina, were taken at ive places in 1998,
to determine if natural attenuation of PCBs was occurring (Pakdeesusuk et al., 2005). From
an analysis of the mole percentage of each congener of PCB and/or the total of meta -, para -,
and ortho -chlorines and total chlorines per biphenyl, it was determined that solubilization
and desorption were negligible according to mass balances since 1987. In situ dechlorina-
tion was occurring though after an initial rapid rate, followed by a slow rate since 1987.
Microcosm studies supported the indings. There was a lack of information on organic
matter and electron acceptors such as nitrate, sulfate, iron, and manganese, which made it
dificult to predict optimal dechlorination conditions. To reduce the risk of bioaccumula-
tion in ish, capping with fresh sediment may need to be increased.
In 1982, trichloroethene contamination in the groundwater was irst detected at a
Michigan National Priorities List site (An et al., 2004). Since then, samples were taken
in 1991, 1992, 1994, 1995, and 1998, 100 m from the shore and, later, 3 m from the shore.
Anaerobic degradation was indicated as the products of dichloroethene (DCE), vinyl chlo-
ride (VC), ethene, and methane were found. Analysis of the water within the lake sedi-
ments indicated natural attenuation.
At the Columbus Air Force Base, the fate and transport of jet fuel contaminants was
evaluated in sixty sediment samples (Stapleton and Sayler, 1998). Using DNA probes, 10 7
to 10 8 organisms per gram of sediment were founds, compared with 10 4 to 10 6 organisms
per gram by traditional methods. There was evidence of the degradation of BTEX and
naphthalene, particularly after 5 to 7 days. Without nutrient addition, more than 40% of
these 14 C-labeled compounds were mineralized in the sediments. Correlations of labora-
tory assay and ield analyses are required, and thus, further ield tests will be performed.
At the Dover Air Force Base, which was contaminated with chlorinated ethenes, low
biomass levels (<10 7 bacteria per g sediment) were found (Davis et al., 2002). However,
mineralization of vinyl chloride and cis -DCE was found to be occurring. The 16 S rRNA
gene sequence indicated the presence of anaerobic microorganisms capable of anaerobic-
halorespiration and iron reduction. It was concluded that microorganisms were the major
mechanism for reductive and oxidative attenuation of the chlorinated ethenes.