White bass wild-caught and sold commercially contained significantly higher levels of mercury, arsenic and selenium than fish caught near former industrial areas. The University of Pittsburgh study showed mercury levels were 2.2 to 4.8 times higher in fish caught in the Canadian Lake Erie and available commercially than in fish caught near former iron and steel mills on the Allegheny and Monongahela rivers in Pittsburgh. While several of these mills have been closed for many years, the nearby rivers continue to contain high levels of pollution from sewer overflows and active industrial operations.
For the study, researchers used local anglers to catch 45 white bass at two locations in Pittsburgh and bought 10 white bass locally that were caught in the Canadian Lake Erie. They analyzed the fish for levels of mercury, arsenic and selenium. In addition to higher levels of mercury, the store-bought fish had levels that were 1.7 times higher for arsenic and 1.9 times higher for selenium.
"We were surprised by our results since we had hypothesized that levels of contaminants in fish would be higher in specimens caught near once heavily polluted sites," said Conrad D. Volz, Dr.P.H., M.P.H., principal investigator, department of environmental and occupational health, University of Pittsburgh Graduate School of Public Health. "These results indicate to us that purchasing fish from a local market cannot guarantee food safety. We recommend a more rigorous testing program for commercial freshwater fish with particular attention to fish entering the U.S. from other countries."
According to Dr. Volz, the results also may indicate that sediments in Lake Erie remain contaminated because of only relatively recent reductions in industrial pollution and active coal-fired power plant air emissions from facilities located around and to the southwest of Lake Erie, as well as wastewater from plants located on the lake. Mercury, arsenic and selenium are markers for coal-burning pollution through air emissions and water pollution and from fly ash piles that are absorbed into surrounding soil. Fly ash is the residue left after coal burning that is often stored at the plant site.
The results of this research were presented at a special session on "Contaminants in Freshwater Fish: Toxicity, Sources and Risk Communication," on Nov. 7, at the annual meeting of the American Public Health Association in Washington, D.C.
The study was funded by grants from the Highmark Foundation, the DSF Charitable Trust and the Heinz Endowments. Co-authors of the study include Nancy Sussman, Ph.D., Devra Davis, Ph.D., Maryann Donovan, Ph.D., Jeanne Zborowski, Ph.D., Yan Liu, all with the University of Pittsburgh; Sean Brady, Venture Outdoors, Pittsburgh; and Karen Gainey, Kamsport, Pittsburgh.
Adapted from materials provided by University of Pittsburgh Schools of the Health Sciences, via EurekAlert!, a service of AAAS.
Wednesday, 6 August 2008
Store-bought Freshwater Fish Contain Elevated Levels Of Mercury, Arsenic And Selenium
Identifying Canadian Freshwater Fish Through DNA Barcodes
New research by Canadian scientists, led by Nicolas Hubert at the Université Laval in Québec brings some good news for those interested in the conservation of a number of highly-endangered species of Canadian fish.
The use of DNA for automated species-level identification of earth biodiversity has recently moved from being an unreachable dream to a potential reality in the very near future. The potential of mitochondrial DNA in achieving this target has been successfully assessed for all of the Canadian freshwater fish communities and the approach bears some very exciting promise.
The Consortium for the Barcode of Life (CBOL) and the Canadian Barcoding of Life network recently assessed the potential of the Barcode region in diagnosing the entire freshwater fish communities of Canada and Alaska in the context of the fish worldwide campaign.
Hubert and colleagues sampled and barcoded 1360 individuals from 190 species belonging to 27 families and 20 orders and showed that Barcodes are effective for species-level identifications in 93% of the case.
In front of the economic importance and identification challenges associated with fishes, this represents a considerable advance for conservation practices and open new perspectives in ecology.
Journal reference:
1. Hubert et al. Identifying Canadian Freshwater Fishes through DNA Barcodes. PLoS One, 2008; 3 (6): e2490 DOI: 10.1371/journal.pone.0002490
Adapted from materials provided by Public Library of Science, via EurekAlert!, a service of AAAS.
All Tree Biomass Is Created Equal In Forests Of Equal Size, Whether In The Tropics Or Temperate Climes, Says Cornell Biologist
ITHACA, N.Y. -- Does the Amazon River basin thrive with more tree biomass than that along the shores of Opeongo Lake in Canada's Algonquin Provincial Park? Is the Congo Basin more tree biomass-rich than the Argonne Forest in northeastern France? Conventional wisdom answers yes, believing that equatorial and tropical regions have far more tree biomass than places like North America, Europe and Asia.
Conventional wisdom seems to be wrong.
The amount of tree biomass in any two given similar-sized areas, whether in a tropical or temperate clime, is virtually identical, according to a new study in Nature (April 5, 2001) by Karl J. Niklas, Cornell University's Liberty Hyde Bailey professor of plant biology, and Brian J. Enquist, a biologist from the University of Arizona.
The term "biomass" refers to organic matter that can be converted to energy, from agricultural residues to crops, but most commonly wood.
"Most people believe that tree biomass per unit area increases toward the equator and decreases rapidly toward the higher latitudes. Certainly, I thought that was true," says Niklas. "Now, I believe that the data show there is very little difference in total tree-standing biomass across most closed-canopy forested communities. We hope this study changes a common perception."
The implications of the research are far-reaching in terms of plant ecology and evolution, says Niklas. Most people believe that forest biomass increases as you package more species into the same space. This does not appear to be true. He says, "Since our model applies equally well to ancient forests as well as modern ones, we believe the results seen for living tree communities extend into deep evolutionary history."
To learn if biomass differences exist between tropical and temperate areas, the scientists used forest data collected by the late Alwyn Gentry, a noted biologist who died in a plane crash in Ecuador in 1993. The data included information from 227 sites of tropical and temperate
closed-canopy forests on six continents. The researchers gleaned statistical information from forests between the latitudes of 60 degrees north and 40 degrees south, at elevations ranging from 20 meters (22 yards) to 3,050 meters (3,337 yards). In the Nature report, "Invariant Scaling Relations Across Tree-Dominated Communities," the scientists say that the Gentry data was remarkable for its uniformity, abundance, measurements of plant size and the number of plants across the varying latitudes. A few of these communities consisted of only two tree species, while others, near the equator, had well over 300.
With this information, the researchers determined the size distribution of specific tree diameters from each site. Niklas and Enquist then calculated tree biomass, visible from above the ground, in tropical, dry, moist and wet forests, using a formula based on the Gentry data.
Enquist and Niklas found that the effects of biodiversity on tree biomass are not very important, regardless of how many species of trees exist in a forest. Differences between tree species, says Niklas, are not important because "all trees, regardless of species, are competing for sunlight and physical space in much the same way."
The scientists explain that despite a wide global variation in species diversity, equivalent areas of tree-dominated communities have nearly identical size-frequency distributions and nearly equivalent standing biomass. This comes about because "tree species compete for three-dimensional space and sunlight using the same arsenal of biological weapons, regardless of their other species differences" says Niklas. "In terms of the utilization of space and light, a tree is a tree is a tree."
Niklas and Enquist had predicted virtually everything they observed in the Gentry data with a computerized mathematical model, or simulation. The model assumed that the energy gain by a plant from the sun must be used to construct leaves, stems and reproductive organs in a way "that complies with the simple rules of physics," says Niklas. When the model simulates tree growth, reproduction and competition for space and sunlight, "you see them grow and die before your eyes, and you see their community expand and contract until it reaches equilibrium," says Niklas. Once the virtual forest reaches a stable state of death and birth, it exhibits the same properties as observed for real tree-dominated plant communities around the globe, says Niklas.
Adapted from materials provided by Cornell University.
'Fuel For Thought' On Transport Sector Challenges
A report on how Australia can best respond to the environmental and economic challenges arising from its dependence on fossil fuels for transport has just been released in Melbourne.
The report "Fuel for thought – The future of transport fuels" challenges and opportunities addresses two serious issues – the need to dramatically reduce the transport sector’s greenhouse gas emissions and, how to deal with the economic risks associated with increasingly costly and scarce oil supplies.
The report is the result of a year’s deliberations by the Future Fuels Forum (FFF) which was convened by CSIRO to engage leading community, industry and government bodies in discussions about a range of plausible scenarios for establishing a secure and sustainable transport fuel mix to 2050.
Director of CSIRO’s Energy Transformed Flagship, Dr John Wright, said Australia’s transport fuel mix will substantially change in response to issues such as climate change and oil prices.
“Securing access to affordable and sustainable fuel underpins Australia’s economy and way of life and as a nation with relatively high vehicle use, we are vulnerable to the economic, environmental and social impacts of rising oil prices and rising temperatures,” he said.
“In response to these challenges, the Forum believes Australia’s fuel mix will shift in the near term to include the expanded use of diesel, gaseous fuels such as LPG and hybrid electric vehicles, with even greater diversity beyond 2020 that might include hydrogen, synthetic fuels from coal or gas and advanced biofuels that will not impact food production.”
“Securing access to affordable and sustainable fuel underpins Australia’s economy and way of life and as a nation with relatively high vehicle use, we are vulnerable to the economic, environmental and social impacts of rising oil prices and rising temperatures,” Dr John Wright said.
Scenarios developed by the FFF have been subjected to advanced techno-economic modelling and assessment which has produced significant insights into the potential impacts of climbing oil prices and the inclusion of fuel in the government’s emissions trading scheme.
“The future price of oil is uncertain,” Dr Wright said. “The Forum’s scenario modelling shows that if oil production peaks, prices could climb as high as A$8 per litre by 2018 in the most extreme case. This outcome could result in significant social impacts that are likely to adversely affect low income Australians.
“Results such as this could be seen as a catalyst for early action on the development and roll-out of alternative fuel options, low emission vehicle technologies and infrastructure that supports sustainable transport.
“The Forum also modelled the inclusion of retail transport fuel in the emissions trading scheme and found prices are expected to be only moderately impacted – an increase of around 10 cents per litre at a price of A$40 per tonne of carbon dioxide. Even with this relatively small impact, our modelling indicates a steady shift towards low emission fuels and vehicles.”
Against the backdrop of awareness about peak oil, alternative fuels and greenhouse gas emissions, the Forum has sought to present a rational and cohesive view of the challenges and opportunities to be considered for assessment of Australia’s future fuel options.
“CSIRO and the Forum participants hope Fuel for thought will assist in advancing the debate on Australia’s transport fuel needs by providing strategic input to decision makers in industry and government on the options that will need their careful consideration and further research,” Dr Wright said.
An in-depth technical discussion of the modelling conducted by CSIRO on behalf of the FFF is available in the report, Modelling of the future of transport fuels in Australia.
Future Fuels Forum partners include: Australian Automobile Association, Australian Association for the Study of Peak Oil and Gas, Australian Conservation Foundation, ARRB Group, Biofuels Association of Australia, Caltex, Engineers Australia, Future Climate Australia, Heck Group, GM Holden, NRMA, National Transport Commission, Public Interest Advocacy Centre, Queensland Rail, Sasol Chevron, South Australian Government, Victorian Government and Woolworths.
Adapted from materials provided by CSIRO Australia.
Welcome To A New Era In Recycling Of Plastics
In an advance toward a new era in recycling of plastics, scientists in Japan are reporting development of a process that breaks certain plastics down into their original chemical ingredients, which can be reused to make new, high quality plastic. That approach fostered recycling of beverage cans, scrap steel, and glass containers, which are melted to produce aluminum, glass and steel.
However, no process has emerged to depolymerize, or breakdown, the long chains of molecules that make up millions of pounds of polymer, or plastic, materials that are trashed each year. Instead, recycling of certain plastics involves melting and reforming into plastic that is less pure than the original.
Akio Kamimura and Shigehiro Yamamoto report invention of an efficient new method to depolymerize polyamide plastics -- which include nylon and Kevlar -- The technology, still at the laboratory-scale stage, does not require costly pressure chambers, extreme temperatures, or high energy inputs. Rather, it uses ordinary laboratory glassware.
The method relies on ionic liquids, liquids that contain only ions (atoms with an electric charge) and are powerful solvents. Researchers used an ionic liquid that changed nylon-6 into its component compound, captrolactam, and could be recycled and reused multiple times. "This is the first example of the use of ionic liquids for effective depolymerization of polymeric materials and will open a new field in ionic liquid chemistry as well as plastic recycling," the report states.
The article, "An Efficient Method to Depolymerize Polyamide Plastics: A New Use of Ionic Liquids," is scheduled for publication in the July 5 issue of ACS' Organic Letters.
Adapted from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.
Fuel Cell Efficiency May Be Improved With Material With 'Colossal Ionic Conductivity'
A new material characterized at the Department of Energy's Oak Ridge National Laboratory could open a pathway toward more efficient fuel cells.
The material, a super-lattice developed by researchers in Spain, improves ionic conductivity near room temperature by a factor of almost 100 million, representing "a colossal increase in ionic conduction properties," said Maria Varela of ORNL's Materials Science and Technology Division, who characterized the material's structure with senior researcher Stephen Pennycook.
The analysis was done with ORNL's 300 kilovolt Z-contrast scanning transmission electron microscope, which can achieve aberration-corrected resolutions near 0.6 angstrom, until recently a world record. The direct images show the crystal structure that accounts for the material's conductivity.
"It is amazing," Varela said. "We can see the strained, yet still ordered, interface structure that opens up a wide pathway for ions to be conducted."
Solid oxide fuel cell technology requires ion-conducting materials -- solid electrolytes -- that allow oxygen ions to travel from cathode to anode. However, existing materials have not provided atom-scale voids large enough to easily accommodate the path of a conducted ion, which is much bigger than, for example, an electron.
"The new layered material solves this problem by combining two materials with very different crystal structures. The mismatch triggers a distortion of the atomic arrangement at their interface and creates a pathway through which ions can easily travel," Varela said.
Other fuel cell materials force ions to travel through tight pathways with few spaces for the ions to occupy, slowing their progress. Rather than forcing the ions to jump from hole to hole, the new material has "lots of vacant spaces to be occupied," said Varela, so the ions can travel much more quickly.
Unlike previous fuel cell materials, which have to achieve high temperatures to conduct ions, the new material maintains ionic conductivity near room temperatures. High temperatures have been a major roadblock for developers of fuel cell technology.
The research team with Spain's Universidad Complutense de Madrid and Universidad Politécnica de Madrid produced the material and observed its outstanding conductivity properties, but the structural characteristics that enable the material to conduct ions so well were not known until the material was put under the ultra-high resolution microscopes at ORNL.
The paper, a collaboration between researchers at the Universities of Madrid and at ORNL, was published August 1 in Science.
Tuesday, 29 July 2008
First DNA Molecule Made Almost Entirely Of Artificial Parts
Chemists in Japan report development of the world's first DNA molecule made almost entirely of artificial parts. The finding could lead to improvements in gene therapy, futuristic nano-sized computers, and other high-tech advances, they say.
In the new study, Masahiko Inouye and colleagues point out that scientists have tried for years to develop artificial versions of DNA in order to extend its amazing information storage capabilities.
As the genetic blueprint of all life forms, DNA uses the same set of four basic building blocks, known as bases, to code for a variety of proteins used in cell functioning and development. Until now, scientists have only been able to craft DNA molecules with one or a few artificial parts, including certain bases.
The researchers used high-tech DNA synthesis equipment to stitch together four entirely new, artificial bases inside the sugar-based framework of a DNA molecule. This resulted in unusually stable, double-stranded structures resembling natural DNA.
Like natural DNA, the new structures were right-handed and some easily formed triple-stranded structures. The unique chemistry of these structures and their high stability offer unprecedented possibilities for developing new biotech materials and applications, the researchers say.
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