hepta-CDDs were about 0.050 to 0.400 ng/g in Lake Huron and about 

 10.0 in Saginaw Bay. The concentrations of octa-CDD was measured 

 in four of the Great Lakes (Czuczwa and Kites, 1984; Czuczwa and 

 Kites, 1986). The levels ranged from about 0.30 to 4.8 ng/g 

 except Saginaw Bay which had a concentration of about 35 ng/g. 

 The levels measured in the present study were generally higher 

 than those mentioned above except for the Saginaw Bay samples. 



PCDFs at each level of chlorination could be detected 

 in Lake Kuron (Czuczwa and Kites, 1984) . The concentrations of 

 tetra-CDFs were generally lowest, ranging from about 0.080 to 

 0.200 ng/g away from Saginaw Bay and about 3.0 in Saginaw Bay. 

 The hepta-CDFs were found in the highest concentrations. The 

 range of concentrations found outside of Saginaw Bay was about 

 0.20 to 1.0 and in Saginaw Bay the concentration reached about 

 3 ng/g. Again, as with the PCDDs, the levels from the present 

 study are similar, except the Saginaw Bay levels are much higher. 



In addition, Czuczwa et al. (1984) measured the levels 

 of PCDDs and PCDFs in the sediments of Siskiwit Lake which is on 

 Isle Royale in Lake Superior. This site was chosen because 

 atmospheric input is the only potential source of contaminant 

 input. The concentrations of PCDDs and PCDFs at each level of 

 chlorination were detectable but low. For the PCDDs, the hexa- 

 CDD concentration in the surface sediment was lowest (0.010 ng/g) 

 and the octa-CDD level was the highest (0.56 ng/g). The hepta-CDF 

 concentration was lowest for the PCDFs and the hepta-CDF level 

 was highest (0.020 ng/g). The levels found in the present study 

 were generally lower than those measured in Siskiwit Lake for 

 PCDDs and higher for PCDFs. 



There has been considerable debate in the literature on 

 the sources of these compounds to the environment. Kutzinger et 

 al. (1985) presented an overview of PCDD and PCDF sources. 

 Potential sources for these compounds include various chemical 

 manufacturing processes and incomplete combustion. Bumb et al. 

 (1980) published a very controversial paper which indicated that 

 PCDDs are produced in virtually all combustion processes 

 including natural forest fires. Many studies have shown that 

 PCDDs and PCDFs are produced in municipal incinerators (Buser et 

 al., 1978; Czuczwa and Kites, 1984 and references within) and 

 Eitzer and Kites (1986) measured the concentrations of these 

 compounds in atmospheric particulate and vapor phases. Some very 

 recent work (Ballschmitter et al., 1986; Marklund et al., 1987) 

 indicates that automobiles burning leaded gasoline may be the 

 major source of PCDDs and PCDFs to the environment. 



The ratios of congeners found in a sample can provide 

 information on the source of the contamination. Kagenmaier et 

 al. (1986) used this approach and concluded that the PCDDs found 

 in several rivers in southwest Germany were associated with the 

 use of pentachlorophenol . 



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