RESEARCH WATCH

BIODEGRADATION

Groundwater radionuclides Chelating agents used to decontami­nate nuclear facilities can also in­crease the mobility of low-level ra­dioactive liquid wastes disposed in shallow land trenches. S. C. Brooks and colleagues studied effects of aquifer solid-phase surfaces on the bioavailability of cobalt-citrate com­plexes in a simulated groundwater environment. Large amounts of 60Co are disposed in shallow trenches, and citric acid is used in reactor cleaning. Sand with iron coatings adsorbed more organic ligand than sand without the coatings. Bacteria capable of biodegrading the citrate were more active on this material. The authors suggest that this effect was because of nutrient sorption, such as phosphorus, to the iron coat­ings rather than a direct effect of the coatings on bacterial activity. {Environ. Toxicol. Chem. 1997,16, 862-70)

TNT degrader found Nitroaromatic compounds such as the explosive 2,4,6-trinitrotoluene (TNT) have many industrial uses, including dyes, pesticides, pharma­ceuticals, and solvents. Their degra­dation products in soil, wastewater, and air are often toxic. S. Montpas and colleagues reported the first degradation of TNT by a strain of Serratia marcescens isolated from soil in a site contaminated with TNT. The organism used TNT as its sole source of carbon and energy. At an initial concentration of 50 mg/L"1, TNT was totally degraded within two days. Several reduction intermedi­ates, including 4-amino-2,6-dinitro-toluene and 2-amino-4,6-dinitro-toluene, were detected during the biodegradation. The authors also found that rapid degradation of TNT was dependent on the presence of a surfactant that promotes release of degrading enzymes from the micro­organism. (Biotechnol. Lett. 1997, 19, 291-94)

BIOREMEDIATION Petroleum biomarkers Chemical biomarkers in crude oils and petroleum products can be traced unambiguously to biological precursor compounds such as pristane, phytane, hopanes, and steranes. M. Whittaker and S. J. T. Pollard did an empirical study of various biomarkers used to deter­mine source and weathering charac­teristics of petroleum releases to the environment. Five biomarker indices distinguished between crude oils from different geological back­grounds. The tricyclic terpanes:ho-panes ratio was unlikely to change with weathering of crude oil and therefore was the best index for de­termining the source. Low ratios of n-alkanes:hopane and phytane:ho-pane indicated a reduced bioremedi-ation potential of contaminated soil mixtures. They can be used to deter­mine the bioremediation potential of petroleum hydrocarbons in the envi­ronment. {Environ. Toxicol. Chem. 1997, 16, 1149-58)

Surfactants and PAHs Surfactants can aid the bioremedia­tion of PAHs and other low-solubility contaminants in soil and water. K. Jahan and co-workers evaluated the effect on nonionic surfactants in facilitating PAH biodegradation in soil and water. Four commercially

available nonionic surfactants were tested using batch and continuous-flow reactors inoculated with a mixed microbial culture that had been acclimated to PAH. Studies in­dicated that low surfactant concen­trations could promote mineraliza­tion of PAH without causing inhibitory or toxic effects to the cul­ture. This work identified factors used to select an appropriate surfac­tant and provided important infor­mation for the design of an in situ PAH bioremediation system. These include hydrocarbon solubilizing power, sorptive properties, environ­mental fate, and toxicity. {Water En­viron. Res. 1997, 69, 317-25)

CONTROL

Biofilter clogging Filter clogging limits the potential of biofiltration, an otherwise attractive technique for purifying emissions of VOCs. A. R. Pedersen and colleagues reported the kinetics of biofilm growth, which is responsible for clogging, in a laboratory-scale bio­logical trickling filter for treating tol­uene. A rapid colonization of the biofilter occurred within three days. Various toluene-degrading organ­isms were isolated from the biofilm. Pseudomonas putida {P. putida) was chosen as a representative toluene-degrading organism. It detached

Understanding contaminant bioavailability in sediments The toxicity of contaminants in sediments to bottom-dwelling organisms cannot be reliably predicted without knowing the bioavailability of the pollutants. L Standley studied how the bioavailability of dieldrin to an oligochaete (a worm) relates to sediment composition. The partitioning of dieldrin to four different sediments was best explained by the amount of solvent-extractable sedimentary organic matter. Bioaccumulation of dieldrin by the oligochaete was affected by sediment carbon content and organism lipid content. However, significant variability between sam­ples remains, implying that bioavailability is also dependent on specific sediment composition. The author suggests current chemical measures of partitioning do not accurately reflect biological extractability. [Environ. ScL Techno/., this issue, pp. 2577-83)

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from the biofilm during the first three days of growth. P. putida then occurred at a constant 10% level in the active biomass biofilm. Results showed that P. putida degraded only about 11% of the total toluene; thus, changes in nutrient conditions af­fected the process. [Biotechnol. Bio-eng. 1997, 54, 131-41)

GREEN CHEMISTRY

Fish mince films Many natural polymers cannot be used for biodegradable packaging material because they lose strength and barrier properties as a result of changes in humidity and tempera­ture. B. Cuq and co-workers charac­terized the properties of myofibrillar protein-based hydrophilic films used in several previous studies. The films were prepared from fish mince— gutted, headed, and deboned fish. During a temperature increase, the films showed sudden changes in their mechanical properties and spe­cific heat, classically associated with a glass-rubber transition in amor­phous materials. Increasing the wa­

ter content of the film involved a nonlinear decrease in the glass tran­sition temperature. A hydrodynamic theory could not fully explain the plasticizing effect of water on the films using a thermodynamic theory. (Polymer 1997, 38, 2399-405)

HEALTH

CO and hospitalizations Many recent epidemiological studies have reported links between ambient air pollution and hospital­izations. Most have emphasized par­ticulate air pollution and cardiopul­monary disease; relatively few have evaluated cardiac diseases specifi­cally. R. T. Burnett and colleagues investigated the association between ambient air pollution, including CO, and hospitalization due to conges­tive heart failure in 10 Canadian cit­ies. The study found that several am­bient air pollutants (CO, particulates, nitrogen dioxide, and sulfur dioxide) were associated with increased hos­pitalizations of elderly persons with congestive heart failure. The associa­tion with CO was the strongest and most consistent of all pollutants measured. {Epidemiology 1997, 8, 162-67)

Exhaust and lung function Motor vehicles are a major source of air pollution, yet few studies have examined the health of people living near roads with heavy traffic. B. Brunekreef and colleagues used lung function tests to assess the relation­ship in 877 children who lived within 1000 miles of a busy highway in The Netherlands. Particulates and nitrogen dioxide were measured in the children's schools, and separate traffic counts were taken for auto­mobiles and trucks in residential zones where subjects lived. Lower levels of lung function were associ­ated with truck, but not automobile, traffic density. This relationship was strongest for those children living within 300 miles of major roads. (Epidemiol. 1997, 8, 298-303)

VOC-free paints Health concerns led some manufac­turers to produce paints with no VOCs. J. R. Beach and co-workers compared effects of the new VOC-free paint and conventional water-

based paint (which contains some VOCs) on people with asthma in En­gland having known sensitivity to paint odor. In a double-blind cross­over study, 17 asthmatics painted with VOC-free and conventional wa­ter-based interior paint. Lung func­tion tests were done before, during, and after each 60-minute painting session. Reports of wheezing, breathlessness, and other symptoms increased during painting with con­ventional water-based paint, but not with VOC-free paint. The authors concluded that the use of VOC-free paints protects people sensitive to paint odor better than conventional water-based paints. (Eur. Respir. J. 1997, 10, 563-66)

MEASUREMENTS Rapid PAH water analysis A need exists for an inexpensive, simple, and sensitive analytical tech­nique for PAHs in water to supple­ment complicated existing tech­niques. A-L. Nguyen and J. H. T Luong reported the development of a new procedure using solid-phase microextraction (SPME) and cyclo-dextrin-modified capillary electro­phoresis. PAHs are extracted from a 0.1-mL sample by placing a poly-

Radionuclide uptake by zooplankton The susceptibility of zooplankton to radionuclide uptake is an indicator o environmental contamination. R. Jef-free and co-workers studied the up­take of radionuclides by zooplankton in the French Polynesian Pacific. Levels of Po-210 exhibited an un­usual, inverse relationship with zoo­plankton biomass. Validated modelim of observed marine system behavior accounted for the rate of Po-210 in­put, ingestion, and removal by zoo­plankton. Results show that low den­sities of zooplankton can elevate concentrations of radionuclides in surrounding waters. These findings are consistent with recent observa­tions of elevated Po-210 concentra­tions in fish taken from waters that surround the Marshall Islands. The authors say that these results point to vulnerability of marine systems to contamination following leakage of radionuclides from weapons test sites and waste repositories, (Envi-ron. Sci. Technol., this issue, pp. 2584-88)

Modeling biosorption performance Biosorption holds promise as an eco­nomical method for removal of toxic heavy metals from industrial waste­waters. The complicated process, however, is not well understood. The ionic strength and pH of wastewater and the presence of lighter metals such as sodium and calcium can interfere with heavy metal binding to biosorbents. Until now, the influence of these alkaline (earth) metals on heavy metal biosorption has been neglected. S. Schiewer and B. Volesky report on a mathematical model they developed and used to account for the combined influence of these parameters on the uptake of cadmium by a brown alga (Sargas-sum). This model should be useful in the analysis of biosorption perfor­mance and the design of wastewater treatment processes. {Environ. Sci. Technol., this issue, pp. 2478-85)

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