Showing papers by "Edward A. Boyle published in 1982"

Deep Circulation of the North Atlantic over the Last 200,000 Years: Geochemical Evidence

Abstract: Variations in the cadmium/calcium ratio of North Atlantic Deep Water are recorded in the fossil shells of benthic foraminifera. The oceanic distribution of cadmium is similar to that of the nutrients, hence the cadmium/calcium ratio in shells records temporal variations in nutrient distributions. Data from a North Atlantic sediment core show that over the past 200,000 years there has been a continuous supply of nutrient-depleted waters into the deep North Atlantic. The intensity of this source relative to nutrient-enriched southern waters diminished by about a factor of 2 during severe glaciations. This evidence combined with carbon isotope data indicates that the continental carbon inventory may have been less variable than previously suggested.

The chemical mass balance of the amazon plume—II. Copper, nickel, and cadmium

Abstract: Trace element samples spanning the salinity range were collected in the Amazon plume in June 1974 and 1976. In 1976, laboratory mixing experiments using unfiltered river water and seawater were undertaken. The studies show that copper and nickel are unreactive in the Amazon plume on a time scale of a few days: in both field and laboratory studies the elements are related linearly to salinity, so that neither adsorption and precipitation not desorption reactions significantly alter the net flux of these elements. The 1974 field data indicate there may be up to 25% removal of copper, probably biologically, although a conservative interpretation could be entertained if systematic deviations from the resulting copper-salinity plot are ignored. Cadmium behavior was not clearly defined. There is some indication of desorption, and the estuarine data can be used to set an upper limit on the net flux. The net effective contribution of the elements to the ocean from the Amazon is copper, 24 nmol kg−1; nickel, 4 to 5 nmol kg−1; and cadmium, <0.1 nmol kg−1.

Water chemistry control of cadmium content in Recent benthic foraminifera

Abstract: The micropalaeontology and isotopic chemistry of foraminifera and other fossils have provided a detailed picture of the surface ocean environment during glaciation1,2. Less is known about climate-related changes in the deep ocean, although Weyl3 and Newell4 have proposed significant variations on theoretical grounds. It is clear that significant variations in the population assemblages and δ13C of benthic foraminifera occur5,6 but these changes do not yet constrain a unique hydrographical solution. Adsorption of phosphate onto calcite and unfavourable solid solution behaviour7,8 preclude direct palaeonutrient determination. Because CdCO3 and CaCO3 form a continuous solid-solution series9 it has been suggested that the trace cadmium variability in foraminifera may provide an additional tool for probing changes in deep ocean circulation10. Here we demonstrate that certain benthic foraminifera, Uvigerina spp. and C. kullenbergi, show a consistent relationship between the Cd/Ca of the bottom water and of their calcite shells.