Distribution of Chlorinated Hydrocarbon Pesticides and PCBs in the ...

a) XAD Water Sampling Validation
Overall column efficiency (defined as percent extraction
efficiency multiplied by percent recovery) was determined by
comparison of concentrations determined by in-situ sampling onto
XAD-2 at 10 m with concentrations from hexane extraction of 10 m
samples collected with a water bottle. The extraction procedure
was carried out in triplicate on 8L aliquots of a sea water
sample collected at 10m depth from the remote hydrohole. Three 8L
samples were filtered through a glass fibre filter (142mm Gelman
AE) into two 4L separatory funnels, spiked with internal standard
(decachlorobiphenyl), then serially extracted with hexane (150mL
then 2 x 100mL ) . The combined extracts were taken down to 6 mL
by vacuum rotary evaporation and sealed into ampoules for GC/ECD
analysis.
The results of the first field XAD validation experiment
carried out August, 1986 in the laboratory on the Ice Island,
indicated extraction of these relatively small sample volumes
(8L), provided useful data only for the most abundant compounds,
(HCHs) , other compounds being below the detection or
quantification limit. The experiment was run in triplicate
(appendix C) but the volatile HCHs were partially lost from one
extract ( sample 2-NBS-X2, fraction 2 ) which had been taken to
dryness during work-up. This sample was not included in the
summary table (Table 3.1) for the calculation of column
efficiency. HCH isomers were quantifiable with a mean a-HCH
concentration of 7050 pg/L, significantly higher than for the in-
situ sampler HCH concentrations ( mean a-HCH 4400pg/L) collected
from the same depth. Based on these compounds, column efficiency
of the a- and gamma- HCHs was 62% and 66%,respectively compared
with hexane liquid-liquid extraction. This contrasts with column
efficency values for gamma-HCH of 89 to 100% determined for these
columns in spiked sea water (Green and Kowalski,l984) and