Vern Hodge

U.S. Mussel Watch: 1977–1978 results on trace metals and radionuclides

Abstract The results of the U.S. Mussel Watch Monitoring Program for the period 1976–1978 for trace metals and artificial radionuclides in bivalves are presented. The substances analysed included Ag, Cu, Zn, Cd, Ni, Pb, 238 Pu, 239+240 Pu and 241 Am. The analyses of organic substances will be presented elsewhere. The concentrations of these substances in the bivalves may reflect upwelling processes, anthropogenic inputs or natural levels. Off the California coast, mussels show markedly elevated Pu and Cd concentrations in coastal areas adjacent to the most intensive upwelling zones. Elevated levels of Pb, for example, are found in organisms living adjacent to highly urbanized places. The general patterns of distribution repeat themselves year after year at a given site. Thus, it is concluded that annual monitoring activities may not be necessary and that a frequency of sampling of several or so years may be more appropriate to identify pollution problems. Finally, national or regional baselines for metal concentrations in bivalves from unpolluted waters are proposed. National baselines for Pb in the west coast mussels of 1·0 parts 10 −6 and for Ag in east coast mussels of 0·05 parts 10 −6 are suggested.

A pollution history of Chesapeake Bay

Abstract Present day anthropogenic fluxes of some heavy metals to central Chesapeake Bay appear to be intermediate to those of the southern California coastal region and those of Narragansett Bay. The natural fluxes, however, are in general higher. On the bases of Pb-210 and Pu-239 + 240 geochronologies and of the time changes in interstitial water compositions, there is a mixing of the upper 30 or so centimeters of the sediments in the mid-Chesapeake Bay area through bioturbation by burrowing mollusks and polychaetes. Coal, coke and charcoal levels reach one percent or more by dry weight in the deposits, primarily as a consequence of coal mining operations.

Some comparative marine chemistries of rhenium, gold, silver and molybdenum

Abstract Four metals, Re, Au, Ag and Mo, whose dissolved forms in seawater can potentially be reduced to insoluble states, have been measured in a variety of solids depositing under anoxic conditions: hydrothermal sulfides; coastal sediments; and phosphorites. For comparative purposes these elements have also been determined in ferromanganese minerals and pelagic sediments which have accumulated under oxidizing conditions. Rhenium appears to be a unique sentinel for identifying reducing depositional environments, where enrichments of greater than three orders of magnitude above crustal concentrations are found. Molybdenum follows Re in these sediments but Mo is enriched also in those that accumulate under oxidizing conditions. The reported Mo crustal concentrations appear low in comparison to our measured sedimentary values. Gold and Ag are concentrated in hydrothermal deposits and sulfides appear to be involved in the precipitation of these elements. Coastal sediments adjacent to a domestic outfall of Los Angeles, California contain extraordinary high accumulations of anthropogenic Au, Ag and Pt. The study seeks an understanding of the mobilities and sinks of these metals in the marine environment during the major weathering cycle. Further, anthropogenic contributions to their sedimentary concentrations are identified.

Some comparative marine chemistries of platinum and iridium

Abstract Iridium has seawater concentrations about one hundred times less than those of platinum, as a consequence of its weaker complexing abilities with halides and of a stronger tendency to hydrolyze. Iridium, like platinum, is enriched in some ferromanganese minerals compared to palladium. Platinum and iridium are probably oxidized during mineral formation from the divalent and trivalent states, respectively, to the tetravalent ones. The pelagic sediment contents of irridium, as well as those of platinum, are related to the manganese contents. For higher platinum contents of the authigenic ferromanganese minerals the Pt/Ir ratios approach the seawater ratio suggesting little dilution by platinum and iridium in detrital minerals. The marked enrichments of platinum and iridium in the ferromanganese concretions enhance their value as potential ores for heavy metals.

Gold in seawater: a conservative view

Abstract Gold concentrations in filtered and unfiltered open ocean Pacific waters give an average of 29 ± 9 pg/l by an atomic absorption/graphite furnace technique preceded by an anion exchange preconcentration step. Similar values (average 37 ± 8 pg/l) were found in nearshore unfiltered waters. These values are geochemically in line with those of golds periodic table neighbors, Pt, Pd and Ag, which also form strong chloro-complexes. On the basis of its more uniform values with depth in seawaters, Au is less reactive in the ocean system than these other metals.

TBT in California coastal waters: monitoring and assessment

Butyltins were monitored at over eighty sites, primarily marinas, in surface waters and sediments of the California coast. Values of tributyltin (TBT) in marina waters ranged from 20 to 600 ppt while lower values were usually found in harbors and on the coast. The origin of the tributyltin is in its use as an antifouling agent in marine paints. In those marinas where the concentrations are greater than about 100 ppt, there is usually a conspicuous absence of native organisms, especially molluscs, which are among the most sensitive animals to the highly toxic TBT. The impact of TBT upon not-target organisms recalls the DDT episode of the 1970s. Increasing uses of TBT-containing antifouling paints in the future may have even more drastic effects on coastal organisms than those observed today. The conclusion is inescapable that TBT should be banned for use in commercially available marine paints.

Preliminary studies on the marine chemistry of ruthenium

Abstract An upper limit for the concentration of ruthenium in surface sea waters off the California coast is estimated to be 5 pg·dm−3 on the bases of laboratory analyses and of theoretical considerations. Ruthenium contents follow those of platinum in ferromanganese nodules. Like the latter element, the former appears to be oxidized from a dissolved state in sea water upon incorporation in the solid phases. Finally, the Pt/Ru ratios in pelagic sediments from the Pacific Ocean cluster around 3 to 4. The platinum metals are associated with the detrital phases and their concentrations are a measure of crustal values.

Marine geochemistry—2: scavenging redux

Inorganic surfaces sorb dissolved and particulate phases from seawater onto organic films from a variety of sources. Heavy metals such as Au, Pt, Mn and Cd come to the coatings primarily from particulate phases. This observation confirms a previous finding of this laboratory for the uptake of U, Pu and Po. With depth in the open ocean there are greater contributions from the dissolved phases. Microbial and photochemical processes can enrich surfaces in some metals through reduction reactions. Copper and Mn enrichments in the films are attributed to the photo-reductions of Cu(II) to Cu(I) and manganese oxides to Mn(II), respectively, while the uptake of Mo is a consequence of the reduction, mediated by organisms, of molybdate to Mo(V) or Mo(IV). Cadmium, on the other hand, appears to be bioaccumulated in the films.