Research M Watch Ambient nitric oxide detector NO is a greenhouse gas, which also contributes to ozone formation and ends up in ecosystems where it may affect forest health. Nearly all atmospheric NO comes from anthropogenic processes, primarily fossil fuel combustion and microbial nitrification and denitrification. However, the compound’s reactive nature makes it difficult to measure at atmospheric concentrations. Determining the 15N/14N isotope ratios of ambient levels of NO as a way to determine the molecule’s source or chemistry is even more challenging. Gerhard Gebauer and Jutta Lauf of the Universität Bayreuth in Germany have closed an important gap by developing a multistep process for determining NO isotopic ratios using isotope ratio mass spectrometry (MS). The key is the sample preparation. NO is collected, concentrated, and separated from contaminants in a series of steps before being reduced to N2 and analyzed by MS. A minimum of 125 nanomoles of NO is needed for an analysis, and mathematical corrections have to be made to obtain accurate results. The authors tested their method by analyzing car exhausts. They found that the isotopic ratios differ between gasoline and diesel cars and were affected by the presence of a catalytic converter and how long the engine had been running (Anal. Chem. 2001, 73, 1126–1133).
Burning sludge increases health risks Adding human sewage sludge to pulverized coal is one way to reduce CO2 emissions from coal-fired power plants, but a team of American and German researchers report it might not be the healthiest way. Jost O. L. Wendt of the University of Arizona, and colleagues at the Arizona Health Sciences Center and Universität Stuttgart in Germany, exposed mice to particulate matter from
the combustion of a sludge–coal mixture and compared the effects with those observed in mice exposed to particles from burning coal alone. Significantly more lung damage occurred when the mice inhaled particles from the burning mixture than from the burning coal. The researchers attribute the toxic effects of the sludge–coal particles to high levels of zinc. Zinc concentrations were as much as 14% (by weight) higher in the respirable-sized particles (0.3–2.5 µm in diameter) from the mixture than in the same sized particles from the coal alone. In contrast, there was not much difference between the concentrations of other metals, including selenium, arsenic, lead, and vanadium, in the sludge– coal particles and those in the coal particles. Iron, however, was found to be higher in the coal particles than in the sludge–coal particles. On the basis of their findings, the researchers caution against the use of dried municipal sewage sludge as an alternative “green” fuel, even though it cuts down on CO2 emissions and helps solve sewage disposal problems (Nature 2001, 409, 998).
PAHs were detected most frequently and at the highest concentrations. Fluoranthene was the most frequently detected PAH and also had the highest concentration (26,000 µg/kg) of any compound measured. Bis(2-ethylhexyl) phthalate was the most frequently detected phthalate and had the highest concentrations (17,000 µg/kg). Phthalate concentrations were also correlated with PAH concentrations. The magnitude of PAH contamination is 10 times greater near cities than in other areas. This signal is so strong that if just 16% of a river basin is urbanized, PAH levels in sediment will probably be high enough to cause adverse ecological effects, according to USGS scientists Thomas Lopes and Edward Furlong. The authors used a range of sediment quality guidelines to estimate adverse effect thresholds (Environ. Toxicol. Chem. 2001, 20 (4), 727–737).
Highest levels of PAHs and phthalates Sediments from rivers in the northeast and Great Lakes region of the United States have the highest levels of polycyclic aromatic hydrocarbons (PAHs) in the country, according to a U.S. Geological Survey (USGS) study. It is the first to use consistent sampling and chemical analysis methods for semivolatile compounds on a national scale. USGS researchers took samples from 536 sites in 20 major river basins across the country. The 65 compounds measured in the study included 27 PAHs, 6 phthalates, and 6 phenols. These semivolatile compounds can accumulate in sediments to concentrations that are toxic to benthic organisms.
Particulates linked to harmful health effects A major new study has strengthened the relationship between inhaling particulates from the air and illness. William Dab of the Association for the Prevention of Air Pollution, Le Kremlin–Bicêtre, France, and coworkers explored in detail the relationship between short-term—a few days—exposure to fine (inhalable) particles and cardiopulmonary mortality. They did this by carefully examining previously reported reviews of 57 published studies involving observations collected in 37 cities worldwide. The French team’s study is especially significant because they
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systematically analyzed all of the judgement criteria upon which the past studies were based and then used that framework to classify all of the arguments presented as either for or against a causal relationship. The French researchers conclude that, on the combined strength of the available evidence, the relationship between health and particulate inhalation is both valid and causal. They note, however, that no individual researcher has yet categorically stated a conclusion that such a causal relationship exists. The researchers suggest that in Europe, inhalable diesel particulate emissions are probably the root cause of observed health problems; however, in the United States, because the origin of inhalable particulates is more complex, the evidence is less clear for attributing such a cause-and-effect relationship (J. Air Waste Manage. Assoc. 2001, 51, 220–235).
and inadequate worker training and public awareness campaigns. They argue that, for the law to be effective, a better management system must be identified and implemented. Wang and Nie recommend remedial strategies in three key areas: institutional reform, technology development, and new legislation and administration. Accomplishing this, they say, will require improvements in efficiency such as unifying legislative responsibilities into one body. Internal investments and technology transfers aimed at modernizing approaches for handling the waste stream and sounder regulatory systems are also needed, including provisions for enforcement and training programs. Both researchers strongly encourage adoption of a fee-based (polluter pays) system for waste management and source separation of economically recoverable materials (J. Air Waste Manage. Assoc. 2001, 51, 264–272).
Fires not sole cause of high tropospheric ozone
Managing China’s trash First, it was a trickle, then a stream, then a river, and now a sea. As its economy continues to expand, China finds itself faced with an ever-growing ocean of municipal solid waste (MSW). The discarded materials are causing serious pollution problems, and there is heightened interest to improve the situation—experts peg the existing pile of waste at 6 billion tons. In 1995, the Chinese government tried to address this issue by enacting the Act of Prevention and Control of Solid Waste Pollution to the Environment, a law that institutes source minimization, recycling, treatment, and disposal in an environmentally sound manner. So far, it has had a limited impact. The problems persist, say Hongtao Wang and Yongfeng Nie, researchers at Tsinghua University in Beijing, because along with poor administration and enforcement, there are funding shortages, limited processing facilities, commingled collection of recyclable materials with other wastes, 190 A
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Although ozone levels are high during intense biomass burning, fires are not the sole culprit of elevated ozone levels in the troposphere, report Anne Thompson of NASA–Goddard Space Flight Center and colleagues. Ozone forms as an indirect result of biomass burning. The combustion byproducts—nitrogen oxides, carbon monoxide, and hydrocarbons—are precursors to ozone formation, which occurs during subsequent photochemical reactions. On the basis of data collected with the orbiting Earth Probe-Total Ozone Mapping Spectrometer (EP/TOMS) over Indonesia before, during, and after devastating fires, the researchers find that intercontinental transport, large-scale dynamics, and lightning are also significant contributing factors to the distribution of high-level tropospheric ozone. EP/TOMS has been monitoring aerosol levels and tropospheric ozone since 1996 on a daily basis with 1° latitude by 1.25° longitude resolution. The data have been used to follow annual pollution variability and trends. Its first significant collection event was during the 1997 El Niño–Southern Oscillation and Indian Ocean Dipole periods, when fires following a drought in Indonesia
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blew pollution across the area. Climate indices and historical data from Nimbus 7/TOMS, a similar data collection probe operating from 1979 to 1997, helped to confirm that seasonal dynamics are a definitive cause of heightened ozone levels. Researchers also note that ozone maxima and peak burning seasons do not directly correlate above, below, and at the equator, and peak seasons occur at different times of the year (Science 2001, 291, 2128–2132).
Tropical clouds could reduce global warming High-level, heat-trapping cirrus clouds over the tropical Pacific Ocean appear to decrease when sea surface temperatures increase. This “natural vent” provides a heat release mechanism so strong that it could significantly diminish global warming, according to Massachusetts Institute of Technology meteorologist Richard Lindzen and colleagues at the NASA–Goddard Space Flight Center. The researchers compared detailed daily observations of cloud cover from Japan’s GMS-5 Geostationary Meteorological Satellite with sea-surface temperature data from the U.S. National Weather Service’s National Centers for Environmental Prediction from January 1998 to August 1999. The data revealed that fewer cirrus clouds are produced over warmer ocean regions. For each degree Celsius rise in ocean surface temperature, the ratio of cirrus cloud area to cumulus cloud area over the ocean dropped 17–27%. When first presented in 1999, the study sparked interest and controversy (Environ. Sci. Technol. 1999, 33 (23), 489A). The authors propose that higher ocean surface temperatures directly cause the decline in cirrus clouds by changing the dynamics of cloud formation and rainfall. Thick, bright clouds like cumulus shield the atmosphere from incoming solar radiation. Thin, icy cirrus clouds are efficient insulators that trap energy rising from the Earth’s surface. The researchers estimate that this venting effect could cut by two-thirds the projected increase in global temperatures initiated by a doubling of carbon dioxide in the atmosphere (Bull. Am. Meteorol. Soc. 2001, 82 (3), 417–432).
