Research M Watch Crypto on a chip
pathogens, say the researchers, who envision using it in micro-total analysis systems and DNA-array chips for monitoring pathogens in the environment. (Anal. Chem. 2001, 73, 2952– 2958)
The breakdown of discarded polyurethane foam may account for some of the BDEs found in the sludges. More than half of the sewage sludge produced annually in the United States is applied to land; in 1998, that amounted to roughly 4 million tons. Because Hale’s group has detected BDEs in 87% of the fish sampled in Virginia waters, their findings indicate that “significant environmental release of these pollutants is occurring in the United States and that humans may be exposed to them through their diet.” The compounds are also detectable in urban and rural air, indicating the potential for longdistance atmospheric transport. Hale concludes that “BDEs are an importantbut generally unrecognizedpersistent organic pollutant in the United States.” (Nature 2001, 412, 140−141)
Flame retardants fire concern over sewage sludge The presence of high concentrations of brominated diphenyl ethers (BDEs) in U.S. sewage sludges suggests that the environmental consequences of land application of sewage sludge need further investigation, according to scientists led by Robert C. Hale of the Virginia Institute of Marine Science. Hale’s group was the first to analyze U.S. sewage sludge for BDEs, which are widely used as flame retardants. The European Commission has © ACS 2001, ANAL. CHEM.
A team of researchers at Cornell University and the National Institute of Standards and Technology have developed a microfluidic chip capable of detecting the waterborne pathogen, Cryptosporidium parvum. The approach relies on amplification of mRNA produced by viable C. parvum in response to heat shock, so only infective oocysts are detected. The chip uses a hybridization scheme, in which mRNA amplified by nucleic-acid-sequence-based amplification (NASBA) is sandwiched between capture probes and reporter probes in a microfluidic channel. The reporter probes are labeled with carboxyfluorosceinfilled liposomes, which generate a much stronger fluorescent signal than single fluorophores, allowing increased sensitivity.
Fluorescent images of microfluidic channels showing (a) a negative Cryptosporidium sample and (b) a positive Cryptosporidium sample.
By integrating the assay onto a microfluidic chip, less reagent and sample are needed, multiple analyses can be performed simultaneously, and sample preparation and detection can be accomplished on the same device. According to the researchers, however, the greatest advantage is the low cost of producing the microdevices, which are made from poly(dimethyl siloxane). The chip-based approach can be readily modified to detect other 362 A
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proposed to ban the formulation commercially known as “Penta” BDE in 2003 because of concerns about its toxicity and tendency to bioaccumulate in humans, but penta-BDE is still used in polyurethane foam in the United States. Hale’s group tested sludges from four different regions and found 1100 to 2290 micrograms (µg) of “Penta-like BDEs” per kilogram (kg) of dry sludge, levels that are 10–100 times higher than amounts reported in European sewage sludges.
ENVIRONMENTAL SCIENCE & TECHNOLOGY / SEPTEMBER 1, 2001
Quantifying carbon sinks in China Carbon storage in Chinese forests is large and has increased markedly since the mid-1970s, reports an international team of scientists from China and Canada. The increases are attributed to extensive government efforts to replant forests. The findings, say Jingyun Fang of Peking University and co-workers, indicate that large-scale afforestation and reforestation projects contribute significantly to storage of carbon in terrestrial sinks. From the late 1970s to 1998, the mean annual accumulation rate of carbon sequestered in forests in China was 0.021 petagrams (1015 g). Total carbon storage in forests in 1998 was 4.75 petagrams. Consistent with the objectives of the Kyoto Protocol, the researchers say the results indicate that using forest management to store carbon in plant biomass provides a way to offset CO2 emissions associated with energy generation and use. Although it has generally been known that forests in the Northern
CO2 sequestration off the coast of Norway The Norwegian Sea could provide safe, long-term storage of carbon dioxide emitted from offshore oil and gas fields, according to computer models developed by Norwegian researchers who are hoping for a largescale demonstration project to test their theory. The team from the Nanssen Environmental and Remote Sensing Center in Bergen, base their model on CO2 released from Haltenbanken, a continental shelf region off the coast of Norway. The researchers predict that if liquid CO2 were injected at 950 m below the sea surface, virtually no gas would escape into the atmosphere. The CO2-enriched water would stay well below the level at which it might mix with upper ocean water. Following normal flows from the Norwegian Sea, the water should enter the northern Atlantic Ocean, traveling through passages between Iceland and Scotland as bottom water, and remain isolated from the atmosphere for centuries. In contrast, injections between 350 and 600 m would allow more than half of the CO2 to escape after 50 years. But CO2 gas makes the water more acidic, possibly threatening deep-sea organisms. To reduce acidity, the researchers suggest pumping CO2 into the sea at different points 5–10 m apart.
The team estimates that it would cost about $13/metric ton of CO2 to inject along an 80-km pipeline at Haltenbanken, excluding expenses for separating exhaust or natural gas. But they say that, even including these costs, the total expense “may become comparable to or even less than” the tax paid for emitting CO2 from offshore installations in Norway ($32/metric ton). (Geophys. Res. Lett. 2001, 28, 2637–2640)
or zigzag-type geometries with wider diameters by straining bond angles and binding energies. Storage capacity for hydrogen in empty spaces increases with diameter. Hydrogen can be stored in the capillary through the tube wall by relaxation “flip-in” and “kick-in” mechanisms, and is released through the outer tube wall with a similar “flip-out” mechanism. The CNT remains structurally strong even after undergoing these activities. (J. Am. Chem. Soc. 2001, 123, 5059–5063)
Nanotubes hold hydrogen Hydrogen has the potential to be a source of clean energy, but attaining viable capacity and safe storage for use in electronics and mobile vehicles is a challenging obstacle. Carbon nanotubes (CNT) possess chemical stability, large surface area, and light mass, making them strong candidates for hydrogen storage. (a)
1.12
(b) 1.44
1.54
d=6.88
d=7.78
(c)
(d)
1.11 1.12 1.56 d=7.13
0.75 d=7.41
1.52
Hydrogen
Carbon
Top view of carbon nanotubes containing adsorbed hydrogen. Configurations include (a) clean, (b) arch-type, (c) zigzag-type, and (d) molecular hydrogens inside the nanotube. d is the average diameter of the nanotube, and bond lengths are in units of angstroms.
Researchers collaborating at Jeonbuk National University in Korea, and Universität-GH Paderborn in Germany, believe that the “road map” to achieving the 6.5 % hydrogen by weight requirement set by the U.S. Department of Energy hydrogen plan is the adsorption mechanism. They have done systematic calculations at absolute zero temperature with CNT for hydrogen adsorption, storage, and extraction and have concluded that this reversible electrochemical storage of hydrogen would be applicable to secondary hydrogen batteries because of the energetically reasonable pathways. Hydrogen ions are adsorbed at the top of the tube, creating stable arch-
Bioremediation in an alpine glacier ski resort
© ACS 2001, J. AM. CHEM. SOC.
Hemisphere contain large amounts of carbon, until now carbon sinks in China had not been well quantified. The data collected and analyzed by Fang and co-workers also indicate that before the institution of government-driven ecological restoration projects, more carbon was emitted than stored in China, largely as a result of deforestation. This finding and the more recent trend of improved sequestration of carbon suggest that government interventions can be beneficial in meeting carbon reduction objectives. Although the Kyoto Protocol does not require China to make firm commitments to limit greenhouse gas emissions, the country has already, as demonstrated by these findings, contributed to efforts to reduce net carbon emissions. (Science 2001, 292, 2320–2322)
An altitude of 2875 m above sea level and mean temperature near 0 ºC may be perfect for skiing, but the conditions are unfavorable for bioremediation because the ground only thaws for two or three months of the year. Even so, Austrian researchers Rosa Margesin and F. Schinner at the University of Innsbruck report that soil chronically polluted with diesel oil from an alpine glacier ski resort can be significantly cleaned up, using a combination of natural attenuation and biostimulation. Natural attenuation is becoming a cost-effective method of remediating oil-contaminated sites, but biostimulation of native microorganisms by restoring inorganic nutrients, such as nitrogen and phosphorus, is still widely used. The microbiologists set fieldincubated lysimeters (mesocosms) containing fertilized and unfertilized soil from the Eisgratferner Glacier in the Tyrolean Stubai Alps in an undisturbed area, where visitors were not allowed, for exposure to natural conditions. Soil and soil leachate samples were monitored during the summers over a three-year period for hydrocarbon concentration and microbial counts and activity. Biological parameters, including microbial counts, catalase activity, and soil respiration, were enhanced by fertilizers, but activity declined with time. After the third summer, the diesel oil level was reduced by 50% and 70% in unfertilized and fertilized soils, respectively. The process of natural attenuation proved to be more effective than biostimulation, although it required more time in these bitter settings. (Appl. Environ. Microbiol. 2001, 67, 3127–3133)
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