No abstract

Iron, manganese, and iron-manganese deposits occur in nearly all geomorphologic and tectonic environments in the ocean basins and form by one or more of four processes: (1) hydrogenetic precipitation from cold ambient seawater, (2) precipitation from hydrothermal fluids, (3) precipitation from sediment pore waters that have been modified from bottom water compositions by diagenetic reactions in the sediment column and (4) replacement of rocks and sediment. Iron and manganese deposits occur in five forms: nodules, crusts, cements, mounds and sediment-hosted stratabound layers. Seafloor oxides show a wide range of compositions from nearly pure iron to nearly pure manganese end members. Fe/Mn ratios vary from about 24 000 (up to 58% elemental Fe) for hydrothermal seamount ironstones to about 0.001 (up to 52% Mn) for hydrothermal stratabound manganese oxides from active volcanic arcs. Hydrogenetic Fe-Mn crusts that occur on most seamounts in the ocean basins have a mean Fe/Mn ratio of 0.7 for open-ocean seamount crusts and 1.2 for continental margin seamount crusts. Fe-Mn nodules of potential economic interest from the Clarion-Clipperton Zone have a mean Fe/Mn ratio of 0.3, whereas the mean ratio for nodules from elsewhere in the Pacific is about 0.7. Crusts are enriched in Co, Ni and Pt and nodules in Cu and Ni, and both have significant concentrations of Pb, Zn, Ba, Mo, V and other elements. In contrast, hydrothermal deposits commonly contain only minor trace metal contents, although there are many exceptions, for example, with Ni contents up to 0.66%, Cr to 1.2%, and Zn to 1.4%. Chondrite-normalized REE patterns generally show a positive Ce anomaly and abundant ΣREEs for hydrogenetic and mixed hydrogenetic-diagenetic deposits, whereas the Ce anomaly is negative for hydrothermal deposits and ΣREE contents are low. However, the Ce anomaly in crusts may vary from strongly positive in East Pacific crusts to slightly negative in West Pacific crusts, which may reflect the redox conditions of seawater. The concentration of elements in hydrogenetic Fe-Mn crusts depends on a wide variety of water column and crust surface characteristics, whereas concentration of elements in hydrothermal oxide deposits depends of the intensity of leaching, rock types leached, and precipitation of sulphides at depth in the hydrothermal system.

Sucralose, the sugar substitute better known to Canadians and Americans as Splenda, hit Norwe gian food markets in 2005. A year later, scientists from the Norwegian Institute for Air Research (NILU) found the chemical to be omnipres ent in the environment-in Oslo Fjord and in raw and treated waste water. Now, scientists in Sweden report finding it completely unchanged in wastewater ef fluent in Stockholm and else where in Sweden.The Swedish environmen tal protection agency (EPA), Naturvårdsverket, commis sioned researchers at the Swedish Environmental Re search Institute (IVL) to ex amine surface waters and wastewater effluent for sucra lose. The researchers report ed in January that samples from both large and small wastewater treatment plants in Sweden had sucralose con centrations of 8 micrograms per liter (µg/L) or more be fore treatment. Larger plants could decrease sucralose concen trations by 10% at most.

The Minamata Convention on Mercury seeks to curb or end most uses of mercury. It also calls for plenty of research.

NAOMI LUBICKT oxicology experiments on nanomaterials often seem to run the same way: put some nanoparticles, carbon nanotubes, quantum dots, or other kind of nanosized structures in a petri dish, water column, soil sample, or lab test tube of choice. Then expose daphnids, microbes, zebrafish, pig lung cells, human skin cells, or other model organisms to the new and exciting materials. Sit back and see what happens.The peer-reviewed literature contains thousands of articles documenting results from these kinds of tests, all conducted in an effort to determine the health and safety of nanomaterials. Despite this, the scientific community has yet to determine which nanomaterials are hazardous to the environment or humans, because of a lack of methodology, metrology, and other basics, including how to actually monitor nanoparticles in air, for example. The diversity of nanomaterials, both existing ones and those to come, also presents a challenge.Researchers say that the field of ecotoxicology and environmental risk assessment of nanomaterials is still in its infancy after less than a decade of concerted effort. And although snapshots from short-term exposure studies are yielding tantalizing glimpses now, the whole picture provided by long-term data on more subtle effects of nanomaterials is completely missing. New methods and collaborations could bring more definitive information soon. Until then, efforts to understand the hazards of nanomaterials continue in a piecemeal fashion.