dated quantitation method that overcomes present difficulties. Phenol compounds were analyzed using an automated, liquid-solid extraction technique followed by LC/MS. These instruments were equipped, depending on die compound being examined, with either atmospheric pressure chemical ionization or ion spray interfaces. When 50-100 mL of river water was processed, limits of detection in full-scan mode ranged from 0.1 to 5 ug/L and from 0.1 to 25 ng/L using a time-scheduled, selective ion monitoring mode. {Anal. Chem. 1997, 69(14), 2756-61)
REMEDIATION Biodegradation of NAPLs Nonaqueous-phase liquids (NAPLs), found in polluted soils, aquifers, and aquatic sediments, often contain toxic constituents that can partition into the aqueous phase and pose human and environmental health risks. D. Morrison and M. Alexander investigated how the biodegradability of toxic constituents is affected by the presence of other chemicals in the nonaqueous phase and by competition for nutrients among the various microbial organisms that can degrade specific chemicals. They found that microbial competition for nutrients and the relative biodegradability of various nonaqueous-phase constituent chemicals can strongly influence the rate of transformation of minor toxic constituents. These interactions must be further understood to design efficient bioremediation strategies at sites that are contaminated with NAPLs. {Environ. Toxicol. Chem. 1997, 16, 1561-67)
RISK Arsenic exposure Although various health effects are associated with extended exposure to arsenic, it is not known whether inorganic arsenic in drinking water at the current maximum contaminant level of 50 ug/L poses a cancer risk in the United States. K. Brown and colleagues evaluated data from two widely used epidemiological studies of cancer and arsenic in drinking water in Taiwan. They conclude that current assessments of
PCB mobility in sediments Although the manufacture and use of PCBs were discontinued in the 1970s, significant atmospheric concentrations persist. It is believed that soils and sediments act as secondary sources of these pollutant compounds. B. Gevao and colleagues studied the vertical distribution of PCBs in dated, lake-bottom sediment cores. They found that upward and downward postdepositional mobilization of these contaminants occurred in the sediments and favored less chlorinated compounds. These findings confirm that the persistence of some PCBs in the atmosphere can be associated with their internal movement within lake-bottom sediments followed by net transfer of lower molecular weight PCBs to overlying waters and ultimately their release to the atmosphere. [Environ. Sci. Techno!., this issue, pp. 3274-3280)
TREATMENT Acid mine drainage Acid mine drainage can degrade the biological activity of streams and render water supplies unfit for use. Wetlands cannot be used as an acid mine drainage treatment method because of failure under high-acid loading conditions. P. Ziemkiewicz and co-workers evaluated treatment of acid mine drainage in open limestone channels with armored limestone (limestone surface-coated with metal hydroxides). Results indicate that properly constructed open limestone channels can provide low-cost, maintenance-free acid neutralization for decades. {J. Environ. Qual. 1997, 26, 1017-24)
WASTEWATER Phosphorus removal
cancer risk, which rely on data taken from these studies, are highly uncertain. Data are too aggregated for reliable dose-response assessment. The authors suggest that further knowledge is needed concerning biological mechanisms mat affect dose-response behavior, and they recommend a new epidemiological study to address current sources of uncertainty. {Hum. Ecol. Risk Assess. 1997, 3(3), 351-62)
Reconciling health statistics In epidemiological studies of health effects associated with air pollution, different statistical models and summary statistics can lead to uncertainties about the consistency of findings. L. Baxter and co-workers report how a simple mathematical technique can be used to derive comparable summary statistics from different regression studies. They used their method to analyze the relationship between air pollutants and human health endpoints—specifically, effects such as mortality and lung function, which are identified with exposure to ozone and suspended particulates. Results show that a variety of studies produce similar findings when statistical outcomes are reported on a common basis by application of the novel technique. {Risk Analysis 1997, 17{3), 273-78)
Phosphorus must be removed from wastewater effluent discharges to safeguard receiving waters from eutrophication. C. Randall and R. Chapin used bench-scale units to investigate the effects of high acetic acid and sodium acetate concentrations in wastewaters on biological phosphorus removal in single-sludge, threestage biological nutrient removal systems. They report that high concentrations of either acetic acid or sodium acetate can cause failure of the biological phosphorus removal system and that progressive failure is typical of bacterial washout. These findings suggest that industrial wastewaters high in acetic acid and phosphorus may not be ideal for treatment using a biological phosphorus removal system. {Water Env. Res. 1997, 69(5), 955-60) Contributors: Michael Brauer, University of British Columbia, Vancouver; Brian Eitzer, Connecticut Agricultural Experiment Station, New Haven; Stephen Geiger, Remediation Technologies, Inc., King of Prussia, Pa.; Vincent Hand, Miami University, Institute of Environmental Sciences, Oxford, Ohio; Louis Kovach, Ecolife Associates, Wilmington, Del; Geoffrey Nobes, McGill University, Montreal; Raewyn Town, Queen's University of Belfast, Northern Ireland; and Margaret Whittaker, NSF International, Ann Arbor, Mich.
VOL. 3 1 , NO. 11, 1997/ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 4 9 5 A
