Vaughan T. Bowen

The Mussel Watch

The levels of four sets of pollutants (heavy-metals, artificial radionuclides, petroleum components, and halogenated hydrocarbons), have been measured in U.S. coastal waters, using bivalves as sentinel organisms. The strategies of carrying out this programme are outlined and the results from the first years work are given. Varying degrees of pollution in U.S. coastal waters have been indicated by elevated levels of pollutants in the bivalves, which comprised certain species of mussels and oysters and were collected at over one hundred localities.

U.S. "Mussel Watch" 1976-1978: an overview of the trace-metal, DDE, PCB, hydrocarbon and artificial radionuclide data.

Data are presented for trace metals, polychlorinated biphenyls (PCBs), aromatic hydrocarbons and /sup 239/ /sup 240/Pu in Mytilus edulis, M. californianus, and Crassostrea sp. collected in the US Mussel Watch program in 1976-1978 from 62 locations on the US east and west coasts. General similarities in geographical distributions of concentrations were present in all 3 years with at least an order of magnitude elevation of concentrations of Pb, PCBs, and fossil fuel hydrocarbons in bivalves sampled near the larger urban areas. Elevated Cd and /sup 239/ /sup 240/Pu concentrations in bivalves from the central California coast are apparently related to enrichments of Cd and nuclear weapons testing fallout /sup 239/ /sup 240/Pu in intermediate depth water of the North Pacific and upwelling of this water associated with the California Current system. Data have revealed no evidence of local or regional systematic elevations of environmental concentrations of /sup 239/ /sup 240/Pu as a result of effluent releases from nuclear power reactors.

Fallout radionuclides in the Pacific Ocean: Vertical and horizontal distributions, largely from GEOSECS stations

Abstract From GEOSECS stations, largely, the 1974 distributions of Pu and of 137 Cs are described in the Pacific Ocean north of about 20°S latitude. Changes in some of these distributions are described from 1978 cruises by the authors. The Pacific exhibited, everywhere, a shallow subsurface layer of Pu-rich water with its concentration maximum at about 465 m in 1974; over a large portion of the central North Pacific a second layer of Pu-labelled water, less concentrated than the shallow layer, lay just above the bottom. Similar features were not observed in the case of 137 Cs. The inventories of both Pu and 137 Cs in the water column at most 1974 stations are substantially greater than those to be expected from world-wide fallout alone; these inventory excesses appear to be attributable to close-in fallout, but only if the ratio Pu/ 137 Cs in this source was much higher than in world-wide fallout. The North Pacific mean ratio of the inventories is 2.2 times that observed in world-wide fallout. Resolubilization of Pu both from sinking particles and from sediments explains peculiarities of its depth distributions. There is little evidence for tracer movement by sliding downward along density surfaces; 137 Cs appears to have moved to depth by downmixing at the edge of the Kuroshio, and then moved horizontally and upward alongσ t contours. The shallow Pu-rich layer shows no coordination with density, salinity or O 2 isopleths. The deep Pu-rich layer is restricted to a narrow range of O 2 concentrations that confirm its origin in the Aleutian Trench and rapid spread southward and laterally. Near-bottom circulation processes have been much more active than here-to-fore described.

Pu and137Cs in coastal sediments

Abstract Analyses are presented of 137 Cs, 238 Pu, and 239,240 Pu, in relation to depth in sediment, in 21 gravity cores. These cores span the ranges of times 1964–1975, and of water depths 12–2000 m; they come from three distinct sedimentation areas off the northeast coast of the United States. Although the ranges of total sediment inventories of 239,240 Pu and of 137 Cs from the various areas hardly overlap, the range of ratios of the inventories of these two nuclides is probably the same in all the areas. In the shallow-water cores the 239,240 Pu/ 137 Cs ratio regularly diminishes with depth in the core, and a tendency is seen for curves of this function to have similar slopes in each area; ratios of 238 Pu/ 239,240 Pu show no change with depth in these shallow-water cores. In the deeper-water cores, the 239,240 Pu/ 137 Cs ratio shows no systematic change with depth, but sometimes the 238 Pu/ 239,240 Pu ratio shows a minimum at the sediment surface, and is much higher deeper in the cores. We believe that these phenomena can be explained in terms of a complicated bioturbational process moving the nuclides, together, down into the sediments, of chemical resolubilization, at depth, of plutonium only, and of its subsequent upward translocation in the interstitial solution. Some re-immobilization of plutonium near the sediment surface is implied, and a mechanism is suggested for this, based on displacement of plutonium from organic complexes by the increasing concentrations, in upper layers of the sediment, of re-oxidized dissolved iron.

St. Peter and St. Paul Rocks: A High-Temperature, Mantle-Derived Intrusion

St. Pauls Rocks, often postulated to be an exposure of the suboceanic mantle, consists of a wider variety of rocks than previously recognized. These perhaps crystallized at different mantle levels, and were subsequently incorporated and mylonitized in a hot but solid intrusion.

241Pu in the marine environment by a radiochemical procedure

Abstract A purely radiochemical method is described for analysis of241Pu in environmental samples. Data are given showing that fallout-contaminated marine samples, of several kinds and provenances, exhibit241Pu/239,240Pu ratios slightly higher than, but not certainly distinguishable from, those reported for fallout-contaminated soils. Such ratios, however, in samples from several planned or accidental Pu releases, are clearly different, suggesting241Pu will be a useful tracer in following the spread of released Pu. The data have also clear implications for the source, and growth, of environmental241Am.

Vertical profile of artificial radionuclide concentrations in the Central Arctic Ocean

Abstract The artificial radionuclides 90 Sr, 137 Cs, 238 Pu, 239,240 Pu and 241 Am have been measured in eight water samples collected in 1979, at intervals from surface to bottom, through the ice at the LOREX satellite camp SS near the North Pole. Differences in the concentrations and ratios of these nuclides, compared with values measured, over time, in the various water masses that flow into the Arctic Ocean, can be used as semi-independent checks on rates of flow to the LOREX stations and on residence times in the Arctic Ocean. An unexpected finding was that water labelled with low-level liquid waste from the Windscale plant on the Irish Sea is a major component of the 1500 m LOREX sample, and has reached there in no more than eight to ten years. Even from this one station in the Polar Ocean, estimation of the inventories of the various radionuclides is good enough to emphasize the importance of horizontal advection of the various supply terms to the Arctic.

Windscale effluent in the waters and sediments of the Minch

A SYSTEMATIC intrusion of water of high 137Cs content into the north-eastern North Sea has been reported by the German Hydrographic Office1. Jefferies et al.2 later confirmed that a stream of water rich in radioactive caesium from Windscale passes northwards through the Hebridean Channel, around the north of Scotland and into the North Sea. Although the circulation pattern with respect to 137Cs has been significantly refined in recent reports3 and from German data for 1975 (ref. 4) and 1976 (Kautsky, personal communication) little attention has been paid to the status of other radionuclides in this stream. Such a study offers, however, an excellent opportunity of looking at the geochemical discrimination between, for example, 137Cs and the transuranic α-emitting nuclides; it seemed also that an examination of the changes of the ratio of 134Cs to 137Cs during this passage would give a good basis for estimation of the travel time. As a part of the Flex Programme (Fladen Ground Experiment—part of Jonsdap 76 international programme on the interplay of environment and a plankton bloom) in the North Sea in May–June 1976, we collected a series of sediment, water and biota samples for that purpose. We report here our analyses of samples from a large-volume water station and a 21-cm diameter sediment core taken in the Minch, 27 May 1976.

Morphology and Sediments of a Portion of the Mid-Atlantic Ridge.

In October 1964, a detailed geophysical and sampling survey was made of the central part of the Mid-Atlantic Ridge between 22� and 23� north latitude. The results indicate a large difference in age between the relief of the crest and that of the flanks of the Ridge and suggest that the crest portion is very young. Detailed surveys of two sediment-filled valleys on the upper western flank of the Ridge reveal different sedimentary sequences in the two valleys and indicate the probable existence of a locally controlled depositional regime and a significant local supply of sediment.

Fallout nuclides in Atlantic and Pacific water columns : GEOSECS data

Funding was provided by the United States Department of Energy under Contract DE-AC02-EV03563.