EDENSPACE SYSTEMS CORP.
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Scientists from Edenspace Systems Corp. demonstrated that these brake ferns can take up enough arsenic to meet the U.S. EPA’s upcoming 10-ppb regulations both in their own lab (main photo) and in a pilot test conducted in Albuquerque, N.M. (inset).
to the patented plant and wondered whether it might also be useful for removing arsenic from water. For the ES&T paper, scientists from Edenspace tested two fern species in water containing arsenic that ranged from 20 to 500 parts per billion (ppb). In all cases, the ferns removed arsenic to well below the new U.S. EPA standard of 10 ppb for drinking water, which will be in force in less than two years. Edenspace also finished a fourmonth pilot study at a city greenhouse in Albuquerque, N.M., in mid-May. “We had a series of 10 treatment cells, each of them connected based on gravity flow,” says Mark Elless, senior scientist at Edenspace. A tray of eight ferns was suspended in each 12-gallon tub,
and city water containing an average of 10 ppb arsenic was pumped through the system at 66–450 gallons per day (gpd). Throughout the study, the system easily reduced arsenic to below the equipment detection limit of 2 ppb, and Edenspace estimates that the pilot setup could have reliably treated up to 4000 gpd, or 50 gpd per fern. A preliminary cost comparison shows that because the ferns require little attention, annual operating expenses for the fern technology would be about 50% of an activated alumina system, one of EPA’s “best available technologies” for arsenic removal from drinking water. But capital costs could be as much as 20% higher than those for activated
Nocturnal chemistry removes NOx When the sun goes down, chemical reactions in the lower atmosphere over the open ocean remove as much nitric oxides (NOx) as daytime photochemical processes, according to research conducted off the northeastern coast of the United States and published by the National Oceanic and Atmospheric
Administration (NOAA) in collaboration with several U.S. universities. This field test is “really the first hard and fast quantification of this nighttime chemistry relative to daytime chemistry,” says NOAA researcher Steven Brown, also the paper’s lead author (Geophys. Res. Let. 2004, 31, L07108). Ozone models and NOx
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alumina if a greenhouse must be constructed, Elless says. These estimates, however, were based on a treatment capacity of 160,000 gpd. This volume is still out of reach for the fern technology and nowhere near the capacity of a city like Albuquerque that treats billions of gallons each day, according to Mike Doyle, the Albuquerque city horticulturist. For now, Edenspace is focusing on small-scale applications. “When the EPA came down with this new standard for arsenic, it really hit the small communities,” Elless says. Another issue that must still be worked out is disposal of the arsenic-laden ferns, for there is currently no agreed-upon procedure. According to EPA guidelines, the ferns would be considered hazardous waste at 100 ppm arsenic or above, making them subject to prohibitive disposal costs. To avoid this expense, Elless envisions a pressing technique to remove aqueous arsenic from the fern fronds after they have been harvested. Fortunately, the procedure would be infrequent: Earlier research showed that the ferns could hold arsenic up to 22,000 ppm, which would take between 6 months and a year at the pilot-scale flow rates, Elless estimates. Edenspace is currently trying to determine whether the technology is practical for use in developing world countries like Bangladesh and Vietnam, which have high levels of arsenic in their drinking water. —JASON GORSS
budgets may be affected. Regulators and researchers care about NOx, which primarily comes from burning fossil fuels, because it reacts with airborne hydrocarbons to form ground-level ozone in sunlight, particularly in urban areas. Although most previous research focused on the daytime chemistry, researchers have speculated that nocturnal processes were an important part of the cycle. During the
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moval of NO3 and N2O5, and therefore NOx, was efficient,” wrote the researchers. But will that apply to air over land and sea everywhere? “We are able to quantify this loss of NOx in this region, and it is likely that the same kind of thing is happening in other regions,” says Brown, “but until we go and make the measurements in other regions we can’t say for sure that the loss is as efficient elsewhere as it is [off the coast of] New England.” The researchers acknowledge that their conclusions may be impacted by the summer season in which they conducted the study. “The chemistry that we looked at may in fact be somewhat different in colder weather,” says Brown. The researchers plan to do cold weather studies and have also been working on equipment that can go on a plane, which would enable them to study the chemistry at different altitudes. In the meantime, what do these measurements mean for modeling? The unexpectedly high rates of NOx removal—2–3 times higher than generally predicted—were measured in a region that includes a lot of aerosols coming off the coast from a major urban area, says Sanford Sillman, an atmospheric chemist at the University of Michigan. Sillman believes that aerosols may play a key role, which underscores the need to achieve the correct link between gas and aerosols in models. —RACHEL PETKEWICH
Kyoto’s ancillary benefits Implementing the Kyoto Protocol could reduce the cost of cutting air pollution, according to a study from the European Environment Agency published in April. The European Union (EU) would spend money on fewer “relatively high-cost” controls needed to meet strict EU emissions targets for air pollutants, says the report, which focuses on Western Europe. The study measured the costs of three different pollution-control scenarios against a baseline and assumes that no new climate policies are implemented. The total cost of implementing air pollution targets could fall by as much as 7% or ¤6.6 billion a year, assuming that emissions trading mechanisms stay within the EU. Exploring the Ancillary Benefits of the Kyoto Protocol for Air Pollution in Europe is at http://reports.eea.eu. int /technical_report_2004_93/en/ technical_report_no_93_web.pdf.
Sustainability declining worldwide
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
day, the NO2 component of NOx reacts with hydroxyl radicals and converts into nitric acid, which deposits onto the ocean’s surface; at night, the reaction involves conversion to nitrate (NO3) or N2O5 and then deposition as acid. However, until recently, researchers lacked an analytical method to quantify N2O5 alone or mixed with NO3. To study the behavior of these two gases, Brown and his group in Colorado developed a method based on cavity ring-down spectroscopy, a sensitive and sophisticated technique that measures light absorption. The debut field test occurred aboard a NOAA ship outfitted with a suite of analytical equipment for measuring trace gases and collecting meteorological data. The researchers investigated the air over the ocean because its depth remains constant, which means that the daytime chemistry can be directly compared to nocturnal chemistry. Conducting the tests near the New England states happened to be a “fortuitous combination of having the detection capabilities and the sampling platform in one place at one time,” Brown adds. The researchers concluded that deposition probably accounts for all of the nitric acid removal from the air, although uptake by sea salt aerosol may play a small role. “The small abundances of NO3 and N2O5 relative to NO2 imply that the re-
Researchers made new measurements that could have important implications for ground-level ozone formation while aboard the Ronald H. Brown, a 274-foot vessel owned by the National Oceanic and Atmospheric Administration.
The world’s environmental health took a turn for the worse between 2001 and 2002, according to The Little Green Data Book 2004. The book relies on a sustainability indicator developed by its publisher, the World Bank, to measure “the true rate of savings in an economy after taking into account investments in human capital, depletion of natural resources, and damage caused by pollution.” This year’s edition of the book documents that this indicator is in a global decline that portends “welfare [will] decrease in the future as a result of decisions made today.” Both the Middle East and Africa are on unsustainable paths, according to this metric, and even Europe, Central Asia, and Latin America have low savings rates. To see a copy of the book, go to www.worldbank.org/ sustainabledevelopment.
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