Eggshell thinning, chlorinated hydrocarbons, and mercury in inland aquatic bird eggs, 1969 and 1970

摘要: In the Upper Great Lakes States, 9 out of 13 species fish-eating birds were found in 1969-70 to have sustained statistically significant decreases eggshell thickness since 1946. Heron eggs taken Louisiana generally displayed a smaller post-46 change than herons Middle West. On lipid basis, mean PCB- and DDE-residue levels exceeded 100 ppm 7 2 Louisiana, average DDE:PCB ratios two regions being 1.25:1 3.9:1, respectively. Individual dieldrin values tended be higher (31.6 13.95 heron from different locations), although reached 10.1 9.4 great blue black-crowned night Wisconsin. BHC averaged 3.01 0.39 Lake States Of examined for mercury, 29% had greater 0.5 ppm, 9% 1.0 on wet-weight basis. Mercury small sample consistently low. The differences mercury between thus similar those chlorinated hydrocarbons. While DDE was prominent factor formore » most groups, especially herons, relation thinning observed, also important groups even though present much amounts. PCB's mergansers, while positively correlated with index grebes negatively mergansers. 33 references, 1 figure, 5 tables.« less