Martha O. Stallard

Platinum and palladium in roadside dust

Automobile catalytic converters apparently release significant quantities of platinum and palladium to the roadside environment. Dust samples collected from broad-leaved plants contained as high as 0.7 ppm of platinum and 2.5 times less palladium. Rains may wash this concentrate into local water systems or the ocean. 8 references, 1 table.

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.

Platinum and the platinum anomaly in the marine environment

Abstract Platinum is markedly enriched over palladium in ferromanganese minerals compared to seawater concentrations of these two elements. This anomalous behavior, similar to that of cerium in the rare earth series, is attributed to the oxidation of platinum from the dissolved divalent state in seawater to the tetravalent state during mineral formation. The platinum to palladium weight ratio in seawaters is around 4.5, in marine sediments around 1, and in ferromanganese nodules between 50 and 1000. Platinum, similar to palladium, shows a nutrient-type profile in seawater.

Defensive chemistry of Navanax and related opisthobranch molluscs

The strategies of chemical defense in marine opistho— b±anchs are reviewed, emphasizing the accumulation of secondary compounds through the food chain and the production of defensive compounds in specialized glands. The structures of several new compounds from Aplysia brasiliana, Bursatella leachii, and Navanax inermis are presented.

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.

Chemical constituents of the digestive gland of the sea hare aplysia california—II. Chemical transformations

Abstract 1. 1. The algal metabolites laurienterol (4) and pacifenol (6) were shown to undergo transformations to aplysin (1) and pacificidiene (7), respectively, within the digestive gland of the sea hare Aplysia californica. 2. 2. The same transformations can be accomplished in in vitro by treatment with acid catalysts. 3. 3. A new compound 8, formed by the 1,4 addition of hydrogen chloride to pacifidiene (7), was obtained from A. californica and subsequently by synt hesis. 4. 4. The bold numbers above refer to the diagrams of the formulae of the figures.

The brasilenols, rearranged sesquiterpene alcohols isolated from the marine opisthobranch aplysia brasiliana

Abstract Two nonisoprenoid sesquiterpene alcohols, brasilenol and epibrasilenol, have been isolated, along with brasilenol acetate, from the digestive glands of the marine opisthobranch Aplysia brasiliana . The structures of these unusual sesquiterpenoids were determined by extensive spectral and chemical analysis and by their mutual conversion to the corresponding α,β-unsaturated ketone, brasilenone. The brasilenols are likely to have a dietary origin, since these compounds have also been observed as natural products of the red seaweed Laurencia obtusa.

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.