L. Webster et al., LONG-TERM MONITORING OF POLYCYCLIC AROMATIC-HYDROCARBONS IN MUSSELS (MYTILUS-EDULIS) FOLLOWING THE BRAER OIL-SPILL, Analyst, 122(12), 1997, pp. 1491-1495
On January 5, 1993, 84 700 t of Norwegian Gullfaks crude oil was relea
sed into the coastal region of south Shetland when the tanker MV Braer
grounded at Garths Ness, A Fisheries Exclusion Zone was designated un
der the Food and Environment Protection Act 1985 (FEPA), prohibiting t
he taking or harvesting of fish or shellfish within the Zone so as to
prevent contaminated products reaching the marketplace, The criteria s
et for lifting of the Order were that the particular species must be f
ree from any petrogenic taint and the concentration of polycyclic arom
atic hydrocarbons (PAHs) must be within the range for reference sample
s. Between April 1993 and February 1995 the Order was progressively li
fted for wild fish, salmon, crustacea, excluding Nephrops norvegicus (
Norway lobster), and molluscs, with the exception of mussels, As part
of the monitoring exercise, mussels from a reference site were transpl
anted in June 1995 to three sites within the Zone, where they were sus
pended in plastic mesh boxes from rafts to a depth of 5 m, Samples wer
e collected at regular intervals over the following 12 months and the
concentration and composition of PAHs mere determined by gas chromatog
raphy with mass spectrometric detection, The total measured PAH concen
tration at the control site increased from 13.7 to 66.1 ng g(-1) wet m
ass of tissue between June 1995 and February 1996, This trend was reve
rsed by July 1996 when the PAH concentration was 12.8 ng g(-1). The me
an across the year for the control site was 24.0 ng g(-1) (SE = 8.9 ng
g(-1), n = 6), A similar seasonal trend in PAH concentration over the
year was observed at all sites within the Zone, but the PAH concentra
tion was consistently greater at these sites, reaching a maximum conce
ntration of 316 ng g(-1) in February 1996, Although no taint was detec
ted in any of the mussels, these results meant that it was not possibl
e to lift the Prohibition Order for mussels, Further monitoring at thr
ee sites outwith the Zone and three sites within the Zone is under way
together with investigations into the specific source of the PAHs.