Os isotopic data from Boston Harbor Sediments indicates that the anthropogenic Os content has decreased significantly since the termination of sewage slidge release in 1991. Unpublished data from Ravizza, Tuit & Bothner.
The map above shows varations in the Os isotopic composition (red numbers reported as 187 Os / 186 Os ratios) in near-surface sediments from Massachusetts & Cape Cod Bays. Ratios below 8 indicate the influence of anthropogenic Os, while the ratio of 8.45 East of Stellwagon Bank is similar to pristene coastal sediments. The Os isotope data support the influence, initially based on measurements of Agconcentrations, that anthropogenic metals are accumulating in Cape Cod Bay. Sewage particulates released near the mouth of Boston Harbor are believed to be the source of these metals. Sediments within harbor & directanalyses of sewage sludge yield very high Os concentrations and low 187 Os / 186 Os ratios. Data from Ravizza & Bother 1996 (GCA V60 p2753-2763)
Publications:
Ravizza, G.E. and M.H. Bothner (1996). Osmium isotopes and silver as tracers of anthropogenic metals in sediments from Massachusetts and Cape Cod bays. Geochim. Cosmochim. Acta, 60, 1787-1796.
1. Reconstructing the Os-isotope Record of Seawater
2. Isotope Topology of the Mantle
3. Partitioning of Os between Mineral Phases in Mantle-derived Rocks
4. Reconstructing the Flux of Extraterrestrial Matter to Earth through Time
6. Continental Weathering and Runoff of Osmium