Environ. Sci. Technol. 1983, 17, 505-505
SIR: Generally speaking, within a family of related compounds (e.g., CBs), the more highly chlorinated substances are more recalcitrant and resistant to microbiological oxidation (1-4). If signification CB biodegradation was occurring in the Lake Ontario sediments, the lower di- and trichloro congeners should become less predominant than the more highly chlorinated CBs in deeper, older sediments (assuming similar loading patterns over time). Table I. Proportions of Di-, Tri-, Tetra-, Penta-, and Hexachlorobenzenes in Lake Ontario Sediments sediment interval, cm
Literature Cited % di-
% tri-
% tetra- % penta-% hexa-
Core No. 1 (Western Basin)a 0-1 1-2 2- 3 3-4 4-5 5-6 0-1 1-2 2-3 3-4 4-5 5-6
From Table I it can be seen that the relative proportion of the lower CBs stays about the same or increases in deeper sediments. While biodegradation may effect the concentrations of CBs reaching the sediments, our results would indicate that microbiological oxidation is not an important process in Lake Ontario sediments. In our opinion, from the core data in our paper and from other cores we have analyzed, there is insufficient evidence to show the occurrence of anaerobic dehalogenation of CBs in these sediments.
25 24 28 41 38 39
35 31 30 24 30 38
17 15 15
9 10 10
5 6 6 4 3 3
Core No. 2 (Eastern Basin) 10 30 21 11 16 13 12 10 8
29 34 32 36 38
19 20 21 20 18
10
7 11 11
11
18 24 21 22 19 10 28 26 26 24 23 25
Western basin (Oliver, Barry G.; Nicol, Karen D. Environ. Sci. Technol. 1982,16, 532). a
0013-936X/83/0917-0505$01.50/0
0 1983 American Chemical Society
(1) Ware, S. A.; West, W. L. US. Environmental Protection Agency, Office of Toxic Substances, Washington, DC, EPA 56012-77-004, 1977. (2) Tucker, E. S.; Saeger, V. W.; Hicks, 0. Bull. Environ. Contam. Toxicol. 1975, 14, 705. (3) Liu, D. Water Res. 1980, 14, 1467. (4) DiGeronimo, M. J.; Nikaido, M.; Alexander, M. Appl. Environ. Microbiol. 1979, 37, 619.
Barry
G. Ollver," Karen D. Nlcol
Environmental Contaminants Division National Water Research Institute Inland Waters Directorate Canada Centre for Inland Waters Burlington, Ontario, Canada L7R 4A6
Environ. Sci. Technol., Vol. 17,No. 8, 1983 505
