Degradative fate of 3-chlorocarbazole and 3,6-dichlorocarbazole in soil.
OBJECTIVE
3-Chlorocarbazole and 3,6-dichlorocarbazole were isolated from Bavarian soils. The stereospecific formation of the isomers of these chlorinated carbazols can be explained by quantum mechanical calculations using the DFT method. It was shown that chlorination of carbazole and 3-chlorocarbazole respectively is preferred via the sigma-complexes 3-chlorocarbazole and 3,6-dichlorocarbazole as the most stable products. The dioxin-like toxicological potential of 3,6-dichlorocarbazole, determined by the Micro-EROD Test, is in the range of some picogram TCDD equivalents per milligram carbazole. The degradative fate of 3-chlorocarbazole and 3,6-dichlorocarbazole was analysed within a long-term study (57 days) in soil.


METHODS
The soil was extracted by ASE (accelerated solvent extraction) and a further clean-up procedure with column chromatography and chromatography with C18-SPE stationary phases. Quantification of 3-chlorocarbazole and 3,6-dichlorocarbazole was performed employing the isotope-dilution method. The samples were measured with high-resolution GC/MS.


RESULTS
The degradation (ln(c/c(0)) vs. time with best-fit line) showed in almost every storage condition a very small degradation (slopes (h(-1)) in -10(-4) range). However, the decay for the controls were two to three times (-28°C) and six times (with sodium azide) higher, than the decrease of 3-chlorocarbazole and 3,6-dichlorocarbazole in the samples of environmental conditions.


CONCLUSIONS
Especially because of the toxicological potential of 3-chlorocarbazole and 3,6-dichlorocarbazole the proven degradative fate is of large interest. The results show that the analysed carbazoles are not readily degradable in this time period.


CONCLUSIONS
The expected results of exponential decay behaviour could not be proven.


CONCLUSIONS
Longer-lasting studies are expected to reveal more accurate half-lives, although it has been shown here, that the compounds are not readily degradable in their native soil environment.
Tröbs
Lisa
L
Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Ecological Chemistry, Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.
Henkelmann
Bernhard
B
Lenoir
Dieter
D
Reischl
Arthur
A
Schramm
Karl-Werner
KW
D000452:Aldrin / Q000737:chemistry; D000818:Animals; D002227:Carbazoles / Q000737:chemistry* / Q000633:toxicity; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D004147:Dioxins / Q000737:chemistry; D006207:Half-Life; D054879:Halogenation; D051381:Rats; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry* / Q000633:toxicity; D013237:Stereoisomerism
C558653:3,6-dichlorocarbazole; D002227:Carbazoles; D004147:Dioxins; D012987:Soil; D012989:Soil Pollutants; D019363:Cytochrome P-450 CYP1A1; D000452:Aldrin; C558654:3-chlorocarbazole