Temporal Trends and Sources of PCDDs and PCDFs in the Great Lakes: Herring Gull Egg Monitoring, 1981-1991

Levels of individual polychlorinated dibenzodioxin (PCDD) congeners were measured in pooled herring gull eggs collected from colonies in the Great Lakes and the St. Lawrence River between 1981 and 1991. Polychlorinated dibenzofurans (PCDFs) were quantified from 1984 to 1991. 2.3.7.8- TCDD, 1,2,3,7,8-PnCDD, 1,2,3,6,7,8-HxCDD, and 2.3.4.7.8- PnCDF were detectable in all samples; 1.2.3.4.6.7.8- HpCDD, OCDD, 2,3,7,8-TCDF, 1,2,3,4,7,8- HxDF, and 1,2,3,6,7,8-HxDF were frequently detected. Eggs from Saginaw Bay, Lake Huron, had the highest PCDD/PCDF levels. Levels of TCDD, PnCDD, and HxCDD declined in most colonies between 1981 and 1984. There were no obvious temporal trends after 1984. Using multivariate analyses, colonies were separated into two classes based upon differences in egg bioaccumulation patterns. PCDD and PCDF patterns in a variety of potential sources were compared to these two herring gull classes. Patterns of PCDD accumulation were similar in herring gull eggs, lake trout, and walleye emphasizing the similarity of these species as regional indicators of PCDD/PCDF contamination