HR: 10:35h
AN: OS32B-02    [Abstracts]
TI: Transport of osmium through an estuary (Long Island Sound) using an anthropogenic isotopic signal
AU: * Turekian, K K
EM: karl.turekian@yale.edu
AF: Department of Geology and Geophysics, Yale University Box 208109, New Haven, CT 06520-8109 United States
AU: Sharma, M
EM: mukul.sharma@dartmouth.edu
AF: Department of Earth Sciences, Dartmouth College 6105 Fairchild Hall, Hanover, NH 03755 United States
AU: Williams Gordon, G
EM: gwyneth.williams@asu.edu
AF: Department of Geological Sciences, Arizona State University PS-F686, Tempe, AZ 85287-1404 United States
AB: Esser and Turekian (ES&T 27:2719,1993) reported the presence of Os in New Haven Harbor sediments that could be ascribed to anthropogenic sources based on the relatively non-radiogenic signature. They ascribed the Os loading, associated with regions of sewage plant discharge, as probably due to research uses primarily in hospitals associated with scanning electron microscopy slide preparation of organic samples. Williams et al (EPSL 145: 341, 1997) showed that the same effect could be observed in Long Island Sound proper with the anthropogenic signature strongest towards New York City. By analogy with the New Haven Harbor study this increase was ascribed primarily to the hospitals on Manhattan. The next step was to sample the water along the track following the sediment sampling. Therefore, sampling of Long Island Sound surface water was undertaken along a traverse from the Whitestone Bridge to Greenwich (CT) in October 1994 and the water samples analyzed at Dartmouth in 2005. The results are shown in Table 1. Table 1: Os isotopes in water from the western part of Long Island Sound (distances are km eastward from the Whitestone Bridge) \begin{tabular}{ccrcr} \hline Sample & Estimated & Water & [Os] Conc & Sediment
& Salinity & ¹⁸⁷Os/¹⁸⁸Os & fmol/kg & ¹⁸⁷Os/¹⁸⁸Os
\hline & & & &
Whitestone Br. & 20 & 0.940 & 49 &
(0 km) & & & &
Station A & 26 & 0.994 & 52 & 0.663
(7 km) & & & &
Station G & 28.8 & 1.019 & 47 & 1.009
(39.8 km) & & & &
\hline \end{tabular} It is evident that the traverse across Long Island Sound is a simple mixing of East River water with an ¹⁸⁷Os/¹⁸⁸Os value of 0.940 and slope water with a putative value of 1.050 (based on the average for most ocean waters). The behavior of Os is conservative and shows no removal in the Sound. As the sediments show a strong anthropogenic impact at Station A and virtually none from Station G eastward (Williams et al. 1997) this sediment pattern represents particle transport rather than a tracking of the water composition.
DE: 1030 Geochemical cycles (0330)
DE: 1040 Radiogenic isotope geochemistry
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 1065 Major and trace element geochemistry
DE: 4875 Trace elements (0489)
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005