RESEARCH WATCH
AIR
Fine particulate monitor Recent evidence indicates an association between fine airborne particulate matter (PM2 5) and severe adverse health effects. EPA recently recommended a new PM2 5 National Ambient Air Quality Standard in addition to the existing PM10 standard. J. L. Battarbee and colleagues describe the use of a portable particle impactor (the Burkard Spore Trap) for providing a continuous, highresolution measure of urban particulates. It could be used for further chemical or microscopic analysis of particle composition to identify cific chemical constituents of PM This method CLDD&CU'S to be more responsive to the fine fraction and therefore could be more relevant to the study of health impacts than the tapered element oscillating microbalance method (Atmos Environ 1997 31(2) 171-81)
Methane sources in municipal landfills Few data are available on the biodegradability of individual refuse components in landfills and how methane production may vary with changes in composition of municipal waste. W. E. Eleazer and colleagues characterized the biodegradability and leaehate toxicity of municipal solid waste components in lab-scale anaerobic reactors. Methane yields increased in the following order: leaves (lowest), branches, newsprint, coated paper, grass, old corrugated containers office paper food waste (highest). Methane production generally increased as cellulose and hemicellulose content increased. Only leaehate from the decomposition of food waste was toxic This information can be useri to estimate the ef~ f p r t of changing rervrling pattern*? fin methane production in landfills report that tunical reev-
Particulate distributions The distribution of airborne particles consists of three modes (coarse, accumulation, and nuclei) roughly corresponding to different production processes. Recent studies suggest that the accumulation mode itself is actually composed of two particle types, the condensation and droplet modes, also associated with different production mechanisms. S. Hering and colleagues analyzed southern California data to determine whether the condensation and droplet modes were present in the total physical particle size distribution as well as in distributions of individual chemical constituents Similar trends were observed in the physical size distribution measured by optical and mobility particle counters and in the chemical SDecies size distributions obtained from impactor measurements These measurements indicate that the accumulation mode is frequently bimodal. (Atmos. Environ. 1997,31(1), 1-11)
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Chromate reduction
Styrene degradation limits Batch cultures of Pseudomonas putida CA-3 can degrade styrene, a common environmental contaminant. But few data are available on its effectiveness in degrading styrene under nutrient-limiting conditions that would normally be encountered in the environment. K. O'Connor and colleagues studied the effects of limiting inorganic nutrients in continuous laboratory culture. They studied expression of styrenedegrading enzymes in P. putida CA-3 cultures under carbon-, nitrogen-, and sulfur-limiting conditions in the absence of primary carbon sources Nutrient-limiting conditions resulted in lower growth
1 1 6 A • VOL. 31, NO. 3, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
rates, but production of styrene enzymes continued at lower levels. 1 ne authors concluded that P putiaa CA-3 should be capable of degrading styrene in the environment or in continuous culture. (Appl. Environ. Microbiol. 1996, 62, 3594-99)
Bioremediation cannot remove chromate and other heavy metals often found as contaminants at sites polluted with organic compounds. Efforts are in progress to use mixed cultures that degrade organic pollutants and biotransform heavy metals into forms that are less toxic or less soluble. H. Shen and co-workers examined the kinetics of chromate reduction during the biodegradation of naphthalene by a mixed culture of Bacillus Kl and Sphingomonas paucimobilis EPA 505. The researchers kinetic model of the mixed culture system The model was then verified by experimental data from a series of experiments with a variety of initial compositions (Biotechnol. Bioeng. 1996, 52, 357-63)
0013-936X/97/0931-116A$14.00/0 © 1997 American Chemical Society
