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showed steeper Eh profiles than estuarine sediments and oiled sediments
were more reducing and showed steeper Eh profiles than unoiled sediments
of the same type. The large Eh change with depth (300mv over
1 cm (lie Grande oiled site) or 2 cm (Aber Wrac'h) suggested that sediments
below these depths are likely anoxic.
Chloride (data not presented) was relatively constant at all depths
in all sites and was near seawater chloride levels (20,000 mg/liter).
The concentrations of dissolved sulfate and methane with depth in each
site are reported in Table 1. No major differences in sulfate concentration
with depth or between cores were observed, _and levels were
similar to seawater values (approximately 800 mgSO, -S/l ). Methane
TABLE 1. Sediment Chemistry 3
SULFATE CHEMISTRY**
DEPTH
(cm)
AMC
4
TREZ-HIR ABER WRAC'H ABER ILDUT ILE GRANDE
(oiled)
ILE GRANDE
(control)
0-5