No abstract

Serum samples from 285 4-year-old Michigan children were evaluated for levels of 11 environmental contaminants. Polychlorinated biphenyls (PCBs) were found in half the samples tested; polybrominated biphenyls (PBBs) in 13-21 percent; dicholorodiphenyl trichloroethane (DDT), in more than 70 percent. Nursing (Mothers' milk) was the principal source of these exposures. Congener-

No abstract

During the period from 1975 through 1978, sediment cores and grab samples were obtained from over 100 sites in lower Saginaw Bay. Selected samples were analyzed for grain size, organic and inorganic carbon, over 30 elements and both cesium-137 and lead-210. The study has revealed an extensive mud deposit in the lower bay covering about 400 km^oriented approximately with bathymetric contours. The clay content of this deposit exceeds 50% toward the center with the mean grain size increasing toward deposit margins. Calcium family elements (Ca, Mg, and inorganic carbon) are preferentially concentrated at the southwestern end of the deposit either because of the distribution of source materials or because of prevailing currents in the system. In contrast, iron and organic carbon exhibit highest concentrations in sediments with highest content of clay-size particles. Most other elements, including contaminant metals (Cr, Cu, Ni, Pb, Zn) have surface concentrations which correlate strongly with concentrations of iron and organic carbon (r>0.9; N = 30).Vertical distributions of radionuclides and contaminant metals reveal a zone of constant activity (or concentration) which extends from the sedimentwater interface to depths ranging from 10 to 25 cm. This zone of uniform composition varies systematically within the deposit, tending to be greatest toward the center, and is probably the resiilt of extensive mixing by zoobenthos (predominantly oligochaetes) . About 90% of the zoobenthos occur within the zone of mixing determined radiometrically. Benthos densities range from 10,000 to 50,000 per m^and are sufficient to completely mix sediments annually. Ill 6,000 yg/cm^/yr in August. The mean flux may be reliably predicted from thermodynamic expressions and the sediment temperature. During the fall months the flux (at constant temperature) is strongly correlated with the numbers of chironomid larvae present. Correlations between other nutrient fluxes and organism densities are generally insignificant. The mean flux of silicon based on pore water concentration gradients and estimates of the effective molecular diffusion coefficient were only about 660 iig Si/cm^/yr. Significantly higher direct fluxes suggest that Si release from sediments is not diffusion-limited but dependent on the rate at which materials dissolve at the sediment-water interface. CONTENTS Abstract iii References • 97

The synthesis of all possible Isomeric nona- and octachlorobiphenyls has been accomplished by the Cadogan coupling of commercially available or synthetic chlorinated anilines in the presence of excess chlorinated benzenes and isoamyl nitrite. 2, 3, 4, 6-Tetrachloraniline was prepared by the chlorination of 2, 4, 5-trichloroaniline. The synthetic polychlorinated biphenyls (PCBs) were characterized by their proton magnetic resonance and mass spectra and their purities determined by gas chromatographic analyses. The PCB standards were used to unambiguously identify the deca-, nona-, and octachlorobiphenyls present in human breast milk and in the commercial PCB preparations Arociors 1268, 1262, 1260, 1254, 1248, 1242, 1016, 1232 and 1221 utilizing high resolution glass capillary gas chromatography.