100 



Fig. 3b. Microbial transformation of individual Aroclor 1232 congeners C/c) 

 in E.xperiment No. 2, PCB initial concentration was at 100 ng/1. 

 Samples collected from the Gulf of Anadyr of the Bering Sea. Station 

 7. Numbers are coherent numbers, sec Table 2 



MPN. cells/ml 

 10^ 



10 



10 



PCBB 



a) 



days 



13 5 10 14 



Fig. 4a. Most probable numbers of SB and PCBB. 



21 



PCB' 



davs 



Fig. 4b. Microbial transformation of individual Aroclor 1232 congeners in 

 Experiment No. 6. PCB initial concentration at 100 ng/1. water from 

 the Chukchi Sea. Station 45. Numbers are coherent numbers, see 

 Table 2. 



Lm^w 



Control, initial 

 composition ot PCB 



3rd dav 



^Jy}^jj-M 



Fig. 5. Microbial transformation of low chlorinated Aroclor 1232 congeners 

 (coherent numbers 5. 8. 15) at Station 4 in the southern Chukchi Sea 

 in August 1988. 



Analysis of PCB congeners, after biological degradation, 

 showed that the decomposition of the chlorinated hydrocarbon 

 is primarily affected by stearic configurations and halogen 

 atom substitutions. The stability of PCB congeners is probably 

 influenced by intermolecular bonds. The decomposition of 

 PCB occurs through the production of arene-oxides, which are 

 substituted with biphenyl molecules in positions 2, 2', 5, 5'. 



Thus, the results show that only low chlorinated biphenyls 

 are subject to rapid microbial decomposition in the arctic and 

 subarctic waters. Many such compounds, however, are only 

 partially transformed, which in turn may be more toxic to 

 marine biota. Highly chlorinated biphenyls. in contrast, are 

 extremely resistant to degradations. Consequently, these 

 compounds may accumulate in the ecosystem and circulate in 

 the marine environment for many decades ( Izrael & Tsyban, 

 1989). 



In summary, the results clearly show the ecological toxicity 

 of chlorinated hydrocarbon pollution in the arctic regions. 

 Because of low arctic temperatures, chemical degradation of 

 xenobiotics is practically absent due to slow rates of microbial 

 transformation. 



100 



