Fróðskaparrit - 31.12.2000, Side 164

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INDIVIDUAL ANALYSES OF MERCURY AND ORGANOCHLORINES
IN MARINE MAMMALS FORM THE FAROE ISLANDS
w.-s. dolphins
□ males
■ females
Bođy length, cm
Fig. 14. The sum oftoxaphene parlars no. 26, 50, and 62 (nos. 32 and 69 where not detected) in white-sided
dolphins, expressed as pg/kg lipid, is plotted vs. body length in cm.
Mynd 14. Samløgan av toksafenparlarunum nr. 26, 50 og 62 (nr. 32 og 69 vórðu ikki ávíst) í hvítskjórutum
springaraspiki, í pg/kg av feitti, er víst sum funktión av hvalalongd í cm.
years of age, whose blubber Mirex concen-
tration was 218 (jg/kg lipid and this is the
same individual that contained markedly
elevated mercury concentrations in com-
parison to the other grey seals, including
the above mentioned 22-year-old.
The results of the analyses on white-
sided dolphin blubber samples are given in
Table 8 and a plot of Mirex concentration
versus body length is shown in Fig. 8. The
results for the pilot whales are given in
Table 10 and Fig. 9. Comparing the con-
centration of Mirex in the juvenile females
of the three species shows that the concen-
tration increases in this order: grey seals <
white-sided dolphins < pilot whales in a ra-
tio of approximately 1:4:8.
The active pesticide isomer, p,p’-DDT,
upon biodegradation, is metabolised to
p,p’-DDE and via a different metabolic
route to p,p’-DDD (WHO, 1979). The or-
tho.para isomer, o,p’-DDT, is a by-product
in the synthesis of the potent pesticide.
Only a small fraction is present in the orig-
inal formulation compared to the para,para
isomer. However, upon biotransformation
and biodegradation in the food chain, after
the pesticide generally has entered the envi-
ronment, the relationship between the con-
centrations of these isomers is altered con-
siderably. Because p,p’-DDE is also per-
sistent and lipid soluble, as is p,p’-DDT, it
has been suggested that the ratio between
the concentration of the parent compound
and the metabolite could be used as an in-
dication of the time elapsed since the parent
compound was originally released into the
environment. However, because the rate of
degradation is both species-dependent and
dose-dependent as well as varying between
the individuals according to sex and age
(Table 12), this comparison can only be
used in a qualitative manner (WHO, 1979).
Of the DDT group, only p,p’-DDT and
p,p’-DDE (Fig. 10) were present in de-
tectable amounts in the grey seal blubber,
although in the adult males small concen-
trations of p,p ’-DDD, mean 60±19 pg/kg