Distribution of Chlorinated Hydrocarbon Pesticides and PCBs in the ...
Distribution of Chlorinated Hydrocarbon Pesticides and PCBs in the ...
Distribution of Chlorinated Hydrocarbon Pesticides and PCBs in the ...
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expected to be lower than at our sampl<strong>in</strong>g location over <strong>the</strong><br />
shelf. An average (upper 100 m) value <strong>of</strong> suspended<br />
particulate organic carbon <strong>of</strong> 9 ug C L-1 was measured by<br />
Gordon <strong>and</strong> Cranford compared to average concentrations <strong>in</strong><br />
this study <strong>of</strong> 2.7 <strong>and</strong> 5.7 ug C L-1 <strong>in</strong> <strong>the</strong> upper 50 m <strong>in</strong> May<br />
<strong>and</strong> August (Table 4.4).<br />
Gordon <strong>and</strong> Cranford collected water <strong>in</strong> 12 L bottles<br />
<strong>and</strong> gravity filtered it through similar Selas Flotronics<br />
silver filters used <strong>in</strong> this study. One possible explanation<br />
for <strong>the</strong> lower than expected concentrations <strong>in</strong> our samples is<br />
that <strong>the</strong> Seastar sampler pumps at a low flow rate <strong>and</strong> even<br />
though large volumes were sampled, only part <strong>of</strong> <strong>the</strong><br />
population <strong>of</strong> suspended particles was collected. The 4 mm<br />
diameter open<strong>in</strong>g on <strong>the</strong> Sw<strong>in</strong>nex filter holders might not<br />
allow particle aggregates to enter <strong>the</strong> filter holders.<br />
Alternatively, concentrations <strong>of</strong> aggreagtes could be low <strong>and</strong><br />
<strong>the</strong> probability <strong>of</strong> collection would be small with <strong>the</strong> pump<strong>in</strong>g<br />
rate used. Tests carried out at B.I.O. <strong>in</strong> <strong>the</strong> summer <strong>of</strong> 1987<br />
after <strong>the</strong> f<strong>in</strong>al sampl<strong>in</strong>g trip showed that <strong>the</strong> low results<br />
might also have been a result <strong>of</strong> crack<strong>in</strong>g <strong>of</strong> <strong>the</strong> filters <strong>in</strong><br />
<strong>the</strong> field with subsequent loss <strong>of</strong> some particulate material.<br />
June samples taken with a collector tube <strong>in</strong> place gave low<br />
suspended particle mass <strong>and</strong> particulate organic carbon<br />
concentrations comparable to those found <strong>in</strong> May 1986 taken<br />
without <strong>the</strong> collector tube. The effect <strong>of</strong> <strong>the</strong> tube appears<br />
to be m<strong>in</strong>or.<br />
Concentrations <strong>of</strong> suspended particulate material under<br />
<strong>the</strong> Ice Isl<strong>and</strong> are as low as those observed <strong>in</strong> <strong>the</strong> deep sea.<br />
The dry weight <strong>of</strong> suspended solids <strong>in</strong> pump samples ranged<br />
from 50 ug/L <strong>in</strong> <strong>the</strong> upper 50 m <strong>in</strong> August to less than 20 ug/L<br />
<strong>in</strong> <strong>the</strong> deeper water on all three trips. Suspended solid<br />
concentrations <strong>in</strong> August were about 3 times higher <strong>in</strong> <strong>the</strong> NBS<br />
drop sampler collections than <strong>in</strong> pump collected samples even<br />
with <strong>the</strong> collector tube <strong>in</strong> place.<br />
Suspended solids <strong>and</strong> POC content were highest <strong>in</strong> <strong>the</strong><br />
upper 50 m <strong>in</strong> August <strong>and</strong> lowest <strong>in</strong> June. Mean C:N ratios on
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