The structures of two environmentally significant
toxaphene congeners, namely, a hexachlorobornane (Hx-Sed) and a heptachlorobornane (Hp-Sed), from the
sediment of two lakes located in Alberta, Canada, have
been characterized by 1H NMR and mass spectrometries. Both lakes were treated in the early 1960s by
the addition of toxaphene, as a pesticide, to the water
column at low microgram per liter concentrations.
Highest toxaphene concentrations were found in sediments of both lakes in slices dated to the early 1960s.
In these slices, the chromatographic pattern
resembled that of the toxaphene standard while, in
more recent slices, the number of chlorinated bornane (CHB) peaks was greatly reduced, with the two
most prominent peaks corresponding to 2-exo,3-endo,6-exo,8c,9b(or 8b,
9c),10a-hexachlorobornane
and
2-exo,3-endo,5-exo,6-endo,8c,9b(or
8b, 9c),10a-heptachlorobornane. Hx-Sed has previously been
identified as one of the major reductive dechlorination
metabolites of toxicant B
(2-exo,3-endo,6,6,8c,9b,10a-heptachlorobornane), one of the most toxic components of the technical mixture. Never before,
however, has it been identified as a persistent
contaminant in the environment.