TABLE 3.

Semiquantitative assessment of the specificity and impact of the PCB dechlorination primed by various brominated biphenyl congeners^a

Bromobiphenyl congener	Bromobiphenyl dehalogenation pathwayb	Dehalogenation specificity		Relative impact of primed PCB dechlorinatione
		First bromine lossc	PCB dechlorination primedd
2	→ BPf	ortho	Flanked meta, N	30
26	→ 2  → BP	ortho	Flanked meta, N	100
2-2	→ 2 → BP	ortho	?g	0
3	→ BP	meta	Flanked meta, N	60h
25	→ 2 → BP	meta	Flanked meta, N	80
25-2	→ 25 → 2 → BP	meta	Flanked meta, N	80
25-3	→ 25 → 2 → BP	meta	Flanked meta, N	120
	→ 2-3 → 2 → BP	meta
25-4	→ 2-4 → 2 → BP	meta	Flanked meta, N	120
	→ 25 → 2 → BP	para	Flanked para, P
245	→ 24 → 2 → BP	meta	Flanked meta, N	100
	→ 25 → 2 → BP	para
345	→ 34 → 4 → BP	meta	Flanked meta, N	80
	→ 35 → 3 → BP	para
4	→ BP	para	Flanked para, P	35
24	→ 2 → BP	para	Flanked para, P	35
4-4	→ 4 → BP	para	Flanked para, P	35
246	→ 26 → 2 → BP	para	Flanked para, P	10
	→ 24 → 4 → BP	ortho

^aAll congeners were tested at a concentration of 350 μM. 

^bEvidence for the dehalogenation pathways shown is reported elsewhere (6). 

^cPosition from which the first bromine of the brominated biphenyl was removed. 

^dThe flanked meta dechlorination is Process N dechlorination. The flanked para dechlorination is Process P dechlorination. Both dechlorination processes occurred together when 25-4-BB was used as a primer. 

^eThe impact on dechlorination of the Aroclor 1260 residue in Woods Pond sediment was estimated relative to the dechlorination primed by 26-BB at 125 days, as measured by decreases in the number of total chlorines per biphenyl and in the fraction of hexa- through nonachlorobiphenyls (Tables 1 and 2). See text for details. 

^fBP, biphenyl. 

^gWe observed small decreases in several penta- and hexachlorobiphenyls and small increases in several tetrachlorobiphenyls as a result of incubation with 2-2-CB, but these changes did not correspond to any known pattern of dechlorination. See text for details. 

^hThis value reflects the activity of a single sample. No dechlorination was primed in the duplicate sample.