A 2-phenylallyl substituent at the end of a PMS chain induced the most effective degradation. Degradation occurs through several mechanisms, including radical, anionic, and cationic depolymerization. {Polymer 1996, 37, 4321-26)
Surfactants and bioavailability Degradation of environmental contaminants such as hexachlorobenzene (HCB) is dependent on the bioavailability of the contaminant in the matrix. Addition of surfactants to the matrix can enhance bioavailability and thus enhance degradation. R L. Van Hoof and C. H. Jafvert studied the reductive dechlorination of HCB in sediment slurries amended by two classes of nonionic surfactants: polyoxehylene (POE) sorbitan fatty acids esters (Tweens) and POE alcohols (Brijs). They found that Tween 80 reduced dechlorination at concentrations well above the critical micelle concentration (CMC) but it enhanced dechlorination at concentrations rinse to the CMC The Brijs s h o w e d r e d u r p d or inhibited dechlorination at all r n n r p n t r a t i o n s tested R p r a u s e t h e Twppns a n d t h e Rrijs i m n r o v e d HCB soluhilitv the pnhanrpd dprhlorination nrohahly rpsultpd from snprific i n t p r a r t i n n s hptwppn thp surfactants a n d thp mi rrnhial mpHia (Fnviran Tnrirnl
chem. 1996, / 5 ( l l ) , 19i4-?4i.
BIOREMEDIATION Selenium in drainage water Irrigation of agricultural land may result in leaching naturally occurring selenium into subsurface drainage water. Disposal of drainage water containing toxic concentrations of selenium has led to serious environmental problems. A. W. Cantaflo and co-workers describe a method for bioremediation of selenium from agricultural drainage water. They used a selenate-respiring bacterium, Thaurea selanatis, to remediate agricultural drainage water in the San Joaquin Valley in California Results indicate that selenium oxyanion concentrations selenate and selenit6 were reduced by 98%' and 9 1 96% of the total selenium recovered was elemental selenium They estimate that widespread use of the
Composting and chlorophenol remediation Chlorophenols (CPs) were widely used at sawmills in Finland to preserve wood, and about 800 sites there must be remediated. Composting in "biopiles" will be the predominant technology. M. M. Laine and K. S. Jorgensen studied degradation of CP-contaminated soil during composting. They constructed four 13-m3 compost piles from mixes of contaminated soil with a combination of bark chips, remediated soil, straw compost, or contaminated wood chips. Each of the four compost mixes showed more than 90% removal of CPs over 12 weeks. The authors observed an initial production of chloroanisoles, with levels declining overtime. Bench scale experiments with the same mixtures showed an average of 60% mineralization of a radio-labeled pentachlorophenol. (Environ. Sci. Techno!., ,his iisue, pp. 377-78)
method in a properly engineered bioremediation system could reduce the amount of selenium deposited in the San Joaquin River from 3000 to 60 kg/year. (Appl. Environ. Microbiol. 1996, 62, 3298-303)
Engineered microbes Improved methods are needed for monitoring the survival and fate of genetically engineered microorganisms (GEMs) in the environment. L. G. Leff and A. A. Leff report the development of a method for detecting GEMs by using a green fluorescent protein (GFP) gene. Survival of Escherichia coll bearing a GFP gene was evaluated in an aqueous environment. GEMs could be enumerated by plating and microscopy using this approach. The GFP had no adverse effects on the host strain. Results demonstrated that E. coli persisted in stream water at higher densities than indicated by conventional culture techniques The GFP has advantages over traditional detection techniques such as culturintr a n d provides a n e w a n d m o r e
accurate tool for trarlcino' r F M s in thp> e m / i r o n m e n t (AnrtI Pmrimn Microbiol 1996 62 3486-88)
HEALTH Traffic-induced asthma Studies have suggested an association between motor vehicle emissions and illness from asthma and other respiratory diseases. H. Duhme and colleagues have reported such an association in a study of adolescents in Bochum, Germany. The group has now found a similar association between traffic density and respiratory illness in Miinster, a city of about 270,000 people. Using a standardized written and video
6 8 A • VOL. 31, NO. 2, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
questionnaire administered to 3700 students, they found an association between self-reported symptoms of wheezing and allergic rhinitis and self-reported levels of truck traffic. The researchers suggest that abraded tire fragments containing potentially allergenic latex particles may be partially responsible for the symptoms. Truck tires contain larger amounts of latex than do automobile tires. (Epidemiology 1996 7 578-82)
MEASUREMENTS Enhanced SFE Supercritical fluid extraction (SFE) is finding numerous applications in the extraction of environmental samples. But extraction of polar analytes remains difficult. T S. Reighard and S. V. Olesik report a modification to SFE, termed enhanced fluidity liquid extraction (EFLE), that can enhance such extractions. An enhanced fluidity liquid is prepared by combining an organic solvent such as methanol with a low-viscosity liquid such as CO- The resultant single-phase liquid is then used in an SFE apparatus to perform the extraction at elevated (but subcritical) temnprature and pressurp The authors evaluated EFLE by extracting 11 phenolic and nitroaromatic pollutants from household dust Rproveries Ynr SPP a n d EPT E wrpre as crnnd as or b e t t e r t h a n Soxhlet extractions for thp s a m p analvtes (Anal Cbpm lQQfi fifl 3fi12-?l1
VOCs in air Rapid methods for monitoring volatile organic compounds (VOCs) are needed to understand a wide range of atmospheric processes and air quality problems. G. L. Kok and colleagues report development of a
New measurements of mercury kinetics Knowledge about the kinetics of Hg(ll) adsorption and desorption on soil is important to predict the transport and fate of contaminants, yet little information has appeared in the literature. Y. Yin and colleagues investigated adsorption and desorption kinetics of Hgjll) on four soil types with a stirred-flow method. A biphasic pattern, involving an initial fast step followed by a slow step, was observed for both adsorption and desorption. Soil organic carbon content was the most important factor in determining Hg(ll) adsorption rates. For soils with higher organic carbon content, the time required to reach equilibrium was increased, as was the fraction of Hg(ll) persistent in the soil. The results may be useful in assessing the risk to groundwater from mercury-contaminated soils. {Environ. Sci. Technol., ,his issue, pp. 496-503)
technique that can measure as little as 0.9 parts per trillion by volume (pptv) of VOCs in a continuous 10min cycle. The reproducibility is 2% or better. The procedure involves drawing air samples through a Tenax cartridge followed by a helium flush. The cartridge then is thermally desorbed into a cooled collection loop for 4 min at 200 "C in 6.5 s to flush the VOCs into a jet separator interface for an ion trap mass spectrometer. MS operates at a rate of one SC3.H p e r second in the full-scan
mode. Ivlethod detection limits range from 0 9 pptv for toluene to 60 pptv for 1 1 1-trichloroethane U.Am. Soc Mass Spectrom 1996 7(11) 1172-76)
POLICY Environmental
justice
Recent studies by church groups, suggest that environmental hazards are distributed disproportionately in disadvantaged communities. S. L. LjUtter and co-workers suggest that such conclusions depend strongly on the geographic scale chosen for analysis. Using South Carolina as an example, they correlated socioeconomic factors with location of toxic and hazardous waste facilities. Spatial analysis at the county level yielded the strongest correlations between low income and toxic sites. Smaller census tract and census block analysis demonstrated only weak correlations. On a statewide basis, there was a disproportionate burden on more affluent, white communities in urban areas, rather than low-income minority communities. The authors suggest that small-scale spatial analyses may be required to resolve claims of envi-
ronmental injustice. {Risk Anal. 1996, 16(4), 517-26)
RISK Data extrapolation Propionaldehyde is a component of gasoline and diesel engine exhaust and cigarette smoke. It is used to make medicines and agricultural chemicals. Few data are available on its human health effects. D. J. Guth tests the hypothesis that the human risk of long-term exposure from propionaldehyde can be determined by comparisons with better studied chemicals of similar structure. Guth compares the kinetics, metabolism, and acute exposure data of propionaldehyde to acetalydehyde and formaldehyde. Based on similarities s u c h 3.S comparable enzyme activity, acute inhalation studies and chemical structures Vie concludes that the noncancer toxicities of these two chemicals can be expected to be similar Guth believes that such extrapolations might avoid the need for costly subchronic and chronic tests {Hum Fcnl RUk Awpw 1199 2R) 580-901
Wildlife exposure Modeling wildlife exposures to toxic chemicals often is used for ecological risk assessments at hazardous waste sites. R. A. Pastorok and coworkers present a comprehensive survey of trends and recent advances in wildlife exposure assessment. This survey includes discussions of the components of basic wildlife exposure modeling, including food web and abiotic exposure pathway analyses Limitations of basic wildlife exposure models, such as the overly conservative and unrealistic nature
of most basic exposure models, are illustrated. Numerous new developments in modeling exposure are provided, including the use of toxicokinetic modeling and Monte Carlo analysis of foraging patterns. {Hum. Ecol. Risk Assess. 1196, 2(3), 445-80)
Wildlife foraging Risk to wildlife that forage in areas with contaminated soil depends partly on spatial factors such as the size of foraging areas and contaminant distribution. J. S. Freshman and C. A. Menzie present two models that incorporate these considerations. One, the Curve Model, is a graphical model that illustrates potential wildlife exposures and effects on individuals, including chronic lethal, reproductive, and acute lethal effects. The second, the Population Effects Foraging Model calculates the average percentage of adversely affected individuals within a. local population A hypothetical hazardous waste site contaminated with a particular chemical is used to illustrate the utility of both models (Hum Ecol Risk Assess 1996 2(3) 481-98)
SOIL Sorption studies Sorption of pollutants in soils can determine their transport, fate, bioavailability, and response to remediation efforts. Although it is known that pollutants become more strongly sorbed with time, the mechanism of this effect is the subject of debate. B. Xing and J. J. Pignatello studied changes in the shape of the adsorption isotherm for the chlorinated aromatic compounds, 1,3-dichlorobenzene, 2,4-dichlorophenol, and metolachlor sorbed to soils after periods of 1, 30, and 180 days. With time, the sorption intensity increased and the concentration dependence decreased Results cire consistent with a dual-mode sorption mechanism including partitioning and site-specific adsorption (Environ Toxicol Chem 1996 ,1 1282-88)
VOC loss in sludge The application of sewage sludge to agricultural land is an increasingly common disposal method. Yet concerns remain about release of volatile organic compounds (VOCs) and
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