David J Hirschberg

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Upper-ocean fluxes of particulate organic carbon (POC) and biogenic silica (bSi) are calculated from four US JGOFS cruises along 1701W using a thorium-234 based approach. Both POC and bSi fluxes exhibit large variability vs. latitude during the seasonal progression of diatom dominated blooms. POC fluxes at 100m of up to 50mmolCm 2 d 1 are found late in the(More)
Atom ratios of 240Pu to 239Pu in bottom sediments from the Fram Strait are used to provide evidence for the long distance dispersion of Pu in the Arctic Ocean. In particular, low (<0.18) 240Pu/239Pu ratios indicate that plutonium from sources in the Kara Sea and Novaya Zemlya is transported across the basin toward the North Atlantic. The results have(More)
The natural radionuclides 234Th and 7Be have known sources in estuaries and strongly and rapidly associate with particles. They are thus good tracers of the transport and sources of particles in the suspended sediment reservoir, and, by implication, of particle-associated contaminants such as heavy metals. In the Hudson River estuary, 234Th is produced from(More)
Transport and source of metal contaminants (Ag, Cd, Cu, Pb and Zn) in the turbidity maximum zone of the Hudson River estuary were studied over the course of a tidal cycle in November 1994 and August 1995. This study showed that the metal/Fe ratios in suspended particles varied more widely than those in the local sediments, implying that sources of metal(More)
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