recovery are desirable from environ mental and cost perspectives. V. Lopez-Avila and colleagues report a microwave-assisted extraction tech nique that can analyze organic pol lutants in solid samples. Using this technique, 5 g of solid material were extracted with 30 mL of 1:1 hexane: acetone in a Teflon-lined extraction vessel—a substantial improvement on the standard Soxhlet extraction, which requires 300 mL of solvent. Twelve samples were extracted si multaneously for 10 min at 115 °C with the microwave at 100% power. The method was tested for the 187 compounds listed in EPA methods 8250, 8081, and 8141A. The results showed acceptable recovery for most compounds, with results equal to or better that Soxhlet extraction in most cases. (Anal. Chem. 1995, 67(13), 2096-102)
Toxicity test errors Determining whether effluents and receiving water containing toxic ma terials pass or fail the acute and chronic toxicity tests required in the National Pollutant Discharge Elimi nation System Permits Program de pends on the results of classical hy potheses tests. However, these tests can result in an erroneous finding of no difference in means because of an inadequate number of replica tions, poor laboratory practices, or large variations in experimental or ganisms and growth media. W. P. Erickson and L. L. McDonald found that correcting these problems could result in declaring meaningless dif ferences statistically significant. The authors propose tests of bioequivalence of control and test media to circumvent these problems. The test of bioequivalence reverses the null hypothesis, which in effect deter mines that treatment concentration and control media are not bioequivalent. (Environ. Toxicol. Chem. 1995, 24(7), 1247-56)
MEΤALS Mercury in lakes W. Wang and C. T. Driscoll investi gated the distribution of Hg in On ondaga Lake, located in central New York. From 1946 to 1970, an adjacent chloralkali facility released Hg into the lake. The lake also has received municipal and industrial effluent discharge for more than a century,
Using iron amendment to immobilize selenium B. A. Manning and R. G. Burau inves tigated an in situ chemical treatment designed to immobilize selenium in evaporation pond sediments from the Kesterson Reservoir in Merced County, CA. They evaluated the amendment of soils with ferrous iron, which oxidizes to form ferric oxyhydroxide, to immobilize selenium based on the affinity of metals for ferric oxyhydroxide during co-precip itation or via adsorption. Soil samples initially contained selenium concen trations ranging from 4 to 29 mg/kg. The influence of FeS04 amendment in soluble Se(IV) was significant: more than 90% was immobilized when Fe(ll) was added in amounts exceeding 50 mmol/kg of sediment. Results pertaining to Se(VI) immobili zation indicated that the initial Se(VI) concentrations strongly affected the outcome. Both selenium species were occluded within the ferric oxy hydroxide produced, suggesting that this treatment may be an in situ re mediation technique for alkaline soils with elevated selenium levels. (Envi ron. Sci. Technol. this issue, 2639-46)
leaving it heavily polluted. The au thors studied how other chemical parameters have affected the pat terns of Hg distribution in the lake. During summer stratification, Hg concentrations increased with depth, accumulating in deeper waters. In creases in Hg in the hypolimnion coincide with elevated H2S concen trations. Stable, soluble species of Hg included HgS2 and Hg(HS)2 when concentrations of H2S ex ceeded those of Hg. The release of Hg from particulate matter is sus pected to contribute to the hypolimnetic accumulation of Hg in the lake. {Environ. Sci. Technol. 1995, 29(9), 2261-66)
POLICY Maintaining biodiversity D. Farrier postulates that biodiversity conservation could be integrated into private land management. Pol icy makers, he claims, have been complacent concerning conservation on federal lands, which make up more than one-third of U.S. land.
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VOL. 29, NO. 10, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY • 4 4 3 A
