Ambient nitric oxide detectorNO is a greenhouse gas, which alsocontributes to ozone formation andends up in ecosystems where it mayaffect forest health. Nearly all atmos-pheric NO comes from anthropogenicprocesses, primarily fossil fuel com-bustion and microbial nitrificationand denitrification. However, thecompound’s reactive nature makes itdifficult to measure at atmosphericconcentrations. Determining the15N/14N isotope ratios of ambient lev-els of NO as a way to determine themolecule’s source or chemistry iseven more challenging.

Gerhard Gebauer and Jutta Lauf ofthe Universität Bayreuth in Germanyhave closed an important gap by de-veloping a multistep process for de-termining NO isotopic ratios usingisotope ratio mass spectrometry (MS).The key is the sample preparation.NO is collected, concentrated, andseparated from contaminants in a se-ries of steps before being reduced toN2 and analyzed by MS. A minimumof 125 nanomoles of NO is needed foran analysis, and mathematical correc-tions have to be made to obtain accu-rate results.

The authors tested their methodby analyzing car exhausts. They foundthat the isotopic ratios differ betweengasoline and diesel cars and were af-fected by the presence of a catalyticconverter and how long the enginehad been running (Anal. Chem. 2001,73, 1126–1133).

Burning sludge increases healthrisksAdding human sewage sludge to pul-verized coal is one way to reduceCO2 emissions from coal-fired powerplants, but a team of American andGerman researchers report it mightnot be the healthiest way.

Jost O. L. Wendt of the Universityof Arizona, and colleagues at theArizona Health Sciences Center andUniversität Stuttgart in Germany, ex-posed mice to particulate matter from

the combustion of a sludge–coal mix-ture and compared the effects withthose observed in mice exposed toparticles from burning coal alone.Significantly more lung damage oc-curred when the mice inhaled parti-cles from the burning mixture thanfrom the burning coal.

The researchers attribute the toxiceffects of the sludge–coal particles tohigh levels of zinc. Zinc concentra-tions were as much as 14% (by weight)higher in the respirable-sized particles(0.3–2.5 µm in diameter) from themixture than in the same sized parti-cles from the coal alone. In contrast,there was not much difference be-tween the concentrations of othermetals, including selenium, arsenic,lead, and vanadium, in the sludge–coal particles and those in the coalparticles. Iron, however, was found tobe higher in the coal particles than inthe sludge–coal particles.

On the basis of their findings, theresearchers caution against the use ofdried municipal sewage sludge as analternative “green” fuel, even thoughit cuts down on CO2 emissions andhelps solve sewage disposal problems(Nature 2001, 409, 998).

Highest levels of PAHs andphthalatesSediments from rivers in the north-east and Great Lakes region of theUnited States have the highest levelsof polycyclic aromatic hydrocarbons(PAHs) in the country, according to aU.S. Geological Survey (USGS) study.It is the first to use consistent sam-pling and chemical analysis methodsfor semivolatile compounds on a na-tional scale.

USGS researchers took samplesfrom 536 sites in 20 major river basinsacross the country. The 65 com-pounds measured in the study in-cluded 27 PAHs, 6 phthalates, and 6phenols. These semivolatile com-pounds can accumulate in sedimentsto concentrations that are toxic tobenthic organisms.

PAHs were detected most fre-quently and at the highest concentra-tions. Fluoranthene was the mostfrequently detected PAH and also hadthe highest concentration (26,000µg/kg) of any compound measured.Bis(2-ethylhexyl) phthalate was themost frequently detected phthalateand had the highest concentrations(17,000 µg/kg). Phthalate concentra-tions were also correlated with PAHconcentrations.

The magnitude of PAH contamina-tion is 10 times greater near citiesthan in other areas. This signal is sostrong that if just 16% of a river basinis urbanized, PAH levels in sedimentwill probably be high enough to causeadverse ecological effects, accordingto USGS scientists Thomas Lopes andEdward Furlong. The authors used arange of sediment quality guidelinesto estimate adverse effect thresholds(Environ. Toxicol. Chem. 2001, 20 (4),727–737).

Particulates linked to harmfulhealth effectsA major new study has strengthenedthe relationship between inhalingparticulates from the air and illness.William Dab of the Association for thePrevention of Air Pollution, LeKremlin–Bicêtre, France, and co-workers explored in detail the rela-tionship between short-term—a fewdays—exposure to fine (inhalable)particles and cardiopulmonary mor-tality. They did this by carefully exam-ining previously reported reviews of57 published studies involving obser-vations collected in 37 cities world-wide. The French team’s study isespecially significant because they

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systematically analyzed all of thejudgement criteria upon which thepast studies were based and thenused that framework to classify all ofthe arguments presented as either foror against a causal relationship.

The French researchers concludethat, on the combined strength of theavailable evidence, the relationshipbetween health and particulate in-halation is both valid and causal.They note, however, that no individ-ual researcher has yet categoricallystated a conclusion that such a causalrelationship exists. The researcherssuggest that in Europe, inhalablediesel particulate emissions are prob-ably the root cause of observedhealth problems; however, in theUnited States, because the origin ofinhalable particulates is more com-plex, the evidence is less clear for at-tributing such a cause-and-effectrelationship (J. AirWaste Manage.Assoc. 2001, 51, 220–235).

Managing China’s trashFirst, it was a trickle, then a stream,then a river, and now a sea. As itseconomy continues to expand, Chinafinds itself faced with an ever-growingocean of municipal solid waste(MSW). The discarded materials arecausing serious pollution problems,and there is heightened interest toimprove the situation—experts pegthe existing pile of waste at 6 billiontons.

In 1995, the Chinese governmenttried to address this issue by enactingthe Act of Prevention and Control ofSolidWaste Pollution to the Envi-ronment, a law that institutes sourceminimization, recycling, treatment,and disposal in an environmentallysound manner. So far, it has had alimited impact.

The problems persist, say HongtaoWang and Yongfeng Nie, researchersat Tsinghua University in Beijing, be-cause along with poor administrationand enforcement, there are fundingshortages, limited processing facili-ties, commingled collection of recy-clable materials with other wastes,

and inadequate worker training andpublic awareness campaigns.

They argue that, for the law to beeffective, a better management sys-tem must be identified and imple-mented. Wang and Nie recommendremedial strategies in three key areas:institutional reform, technology de-velopment, and new legislation andadministration. Accomplishing this,they say, will require improvements inefficiency such as unifying legislativeresponsibilities into one body. In-ternal investments and technologytransfers aimed at modernizing ap-proaches for handling the wastestream and sounder regulatory sys-tems are also needed, including pro-visions for enforcement and trainingprograms. Both researchers stronglyencourage adoption of a fee-based(polluter pays) system for waste man-agement and source separation ofeconomically recoverable materials (J.AirWaste Manage. Assoc. 2001, 51,264–272).

Fires not sole cause of hightropospheric ozoneAlthough ozone levels are high duringintense biomass burning, fires are notthe sole culprit of elevated ozone lev-els in the troposphere, report AnneThompson of NASA–Goddard SpaceFlight Center and colleagues.

Ozone forms as an indirect resultof biomass burning. The combustionbyproducts—nitrogen oxides, carbonmonoxide, and hydrocarbons—areprecursors to ozone formation,which occurs during subsequentphotochemical reactions. On thebasis of data collected with the or-biting Earth Probe-Total OzoneMapping Spectrometer (EP/TOMS)over Indonesia before, during, andafter devastating fires, the research-ers find that intercontinental trans-port, large-scale dynamics, andlightning are also significant con-tributing factors to the distributionof high-level tropospheric ozone.

EP/TOMS has been monitoringaerosol levels and troposphericozone since 1996 on a daily basiswith 1° latitude by 1.25° longituderesolution. The data have been usedto follow annual pollution variabilityand trends. Its first significant collec-tion event was during the 1997 ElNiño–Southern Oscillation andIndian Ocean Dipole periods, whenfires following a drought in Indonesia

blew pollution across the area.Climate indices and historical datafrom Nimbus 7/TOMS, a similar datacollection probe operating from 1979to 1997, helped to confirm that sea-sonal dynamics are a definitive causeof heightened ozone levels. Research-ers also note that ozone maxima andpeak burning seasons do not directlycorrelate above, below, and at theequator, and peak seasons occur atdifferent times of the year (Science2001, 291, 2128–2132).

Tropical clouds could reduceglobal warmingHigh-level, heat-trapping cirrusclouds over the tropical Pacific Oceanappear to decrease when sea surfacetemperatures increase. This “naturalvent” provides a heat release mecha-nism so strong that it could signifi-cantly diminish global warming,according to Massachusetts Instituteof Technology meteorologist RichardLindzen and colleagues at theNASA–Goddard Space Flight Center.

The researchers compared de-tailed daily observations of cloudcover from Japan’s GMS-5 Geo-stationary Meteorological Satellitewith sea-surface temperature datafrom the U.S. National WeatherService’s National Centers forEnvironmental Prediction fromJanuary 1998 to August 1999. Thedata revealed that fewer cirrus cloudsare produced over warmer ocean re-gions. For each degree Celsius rise inocean surface temperature, the ratioof cirrus cloud area to cumulus cloudarea over the ocean dropped 17–27%.

When first presented in 1999, thestudy sparked interest and controver-sy (Environ. Sci. Technol. 1999, 33(23), 489A).

The authors propose that higherocean surface temperatures directlycause the decline in cirrus clouds bychanging the dynamics of cloud for-mation and rainfall. Thick, brightclouds like cumulus shield the atmos-phere from incoming solar radiation.Thin, icy cirrus clouds are efficient in-sulators that trap energy rising fromthe Earth’s surface.

The researchers estimate that thisventing effect could cut by two-thirdsthe projected increase in global tem-peratures initiated by a doubling ofcarbon dioxide in the atmosphere(Bull. Am. Meteorol. Soc. 2001, 82 (3),417–432).

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