Trends in organochlorine residue concentrations and burdens in grey seals (Halichoerus grypus) from Sable Is., NS, Canada, between 1974 and 1994

In blubber from maternal grey seals (Halichoerus grypus) from Sable Is., NS, sigma DDT (p,p'-DDE and p,p'-DDT) concentrations declined from 12 micrograms/g lipid in 1974 to 0.5 microgram/g in 1994. Pup blubber sigma DDT concentrations were about 60% of those of their mothers, and declined at similar rates. In maternal seals, p,p'-DDE increased from 56% sigma DDT in 1974 to 89% in 1994. Polychlorinated biphenyl concentrations did not change between 1976 and 1988, but then declined; the relative proportion of chlorobiphenyl (CB) 101 increased, and those of CBs 170 and 187 decreased between 1985 and 1991. Concentrations of alpha-hexachlorocyclohexane and trans-nonachlor declined after 1988, and of oxychlordane after 1992; concentrations of hexachlorobenzene were constant between 1984 and 1994.     

康滇地轴东缘铅锌矿床铅硫同位素地球化学研究

康滇地轴东缘不同时代碳酸盐地层中铅锌矿床的铅同位素研究表明 ,其2 0 7Pb/2 0 4 Pb与2 0 6 Pb/ 2 0 4 Pb呈良好线性关系 ,2 0 7Pb/ 2 0 6 Pb和2 0 8Pb/ 2 0 6 Pb为一常数。结合对本区矿床的稀土元素及成矿流体地球化学的研究 ,判定不同层位铅锌矿床是在同一个成矿体系同时形成的 ,一次成矿 ,其成矿年龄为 2 4 5Ma(峨眉运动 ) ;同时说明不同矿床成矿金属有相同的来源 ,主要来自上地幔。成矿硫以来自地层中的硫酸盐还原硫为主 ,幔源硫次之。本区铅锌矿床的成矿作用与峨眉山玄武岩的喷流关系密切 ,这是与著名的MVT型铅锌矿床的显著区别。