RESEARCH WATCH Air Excess ozone. Observed tropospheric ozone production rates imply that human activities that add NO to the upper atmosphere lead to production of more ozone than expected. (Wennberg, R O., et al. "Hydrogen Radicals, Nitrogen Radicals, and the Production of Ozone in the Upper Troposphere," Science 1998, 279(5347) 49-53) NOx in the atmosphere. Evidence for the existence of unidentified NOx sinks in the stratosphere suggests that the stratospheric diurnal oddnitrogen cycle is marked by a complex isotope signature that is imprinted on the halogen and HO,,. catalytic cycles. (Zipf, E. C; Prasad, S. S. "Evidence for New Sources of NO in the Lower Atmosphere," Science 1998 279(5348), 211-213)
Assessment Bioaccumulation by aquatic organisms. The current knowledge gap between bioaccumulation and regulations is described. (Bartell, S. M.; La Kind, J. S.; Moore, J. A.; Anderson, P. "Bioaccumulation of Hydrophobic Organic Chemicals by Aquatic Organisms. A Workshop Summary," Int. J. Environ. Pollut. 1998, 9(1), 3-25)
Biodegradation Biodehalogenation of brominated biphenyls. Tested bromobiphenyls were dehalogenated to biphenyl by selected microorganisms. (Bedard, D. L.; Van Dorr, H. M. "Complete Reductive Dehalogenation of Brominated Biphenyls by Anaerobic Microorganisms in Sediment," Appl. Environ. Microbiol. 1998, 64(3), 940-947) Chlorophenol removal. Anaerobic biodegradation of a group of 12 chlorophenols was examined in an unacclimated digester sludge culture and in an acclimated, phenol-enriched methanogenic culture. (Wang, Y-T; Muthukrishnan, S.; Wang, Z.
Photolysis of humic acid Dissolved humic acids account for about half of all organic and almost all colored matter found in natural environments. Knowledge of their photochemistry is required in view of their prevalence and absorptive properties, as well as the possibility for global increases in UV radiation due to ozone depletion. P. Schmitt-Kopplin and coworkers evaluated photochemical degradation of humic acid under nitrogen and oxygen atmospheres and found that irradiation caused compositional and structural changes. Dissolved humic acid underwent selective degradation, especially in an oxygen atmosphere. The lignin and lipid humic constituents were the most affected, while N-compounds, alkyl-aromatics, and carbohydrate components were most resistant to photochemical degradation. These results are important for understanding global carbon cycling. (Environ. Sci. Technol..,his issue, pp. 2533-2541)
"Reductive Dechlorination of Chlorophenols in Methanogenic Cultures," /. Environ. Eng. (Reston, Va.) 1998, 224(3), 231-238) PCB biodegradation. Results indicate that toxicities of PCBs are reduced by microbial dechlorination and that constant proportionality between toxic equivalency and total PCBs cannot be assumed in risk assessments. (Quensen III, J.; Mousa, M.; Boyd, S.; Sanderson, J.; Froese, K.; Giesy, J. "Reduction of Aryl Hydrocarbon Receptor-Mediated Activity of Polychlorinated Biphenyl Mixtures Due to Anaerobic Microbial Dechlorination" Environ. Toxicol. Chem 1998 77(5) 806-813)
"Fate of Adsorbable Organic Halides From Bleached Laundering in Septic Tank Systems," Environ. Toxicol. Chem. 1998, 27(3), 398-403)
Metals Mobility of metals in river soils. A study was performed to identify factors that influence the mobility of accumulated heavy metals in the wetlands soils of a river. (Kalbitz, K.; Wennrich, R. "Mobilization of Heavy Metals and Arsenic in Polluted Wetland Soils and Its Dependence on Dissolved Organic Matter," Sci. Total Environ. 1998, 209(1), 27-39)
Trace metals in humans. Inductively coupled argon plasma mass spectrometry and Zeeman graphite-furnace atomic absorption spectromeTetraethyllead degradation. Gasotry were used to measure 13 metals line hydrocarbons in leaded gasoin the urine of 496 United States resline-contaminated soil retard the idents to establish a reference range biodegradation of tetraethyllead. of concentrations. (Paschal, D. C; (Mulroy, R; Ou, L. "Degradation of Ting, B. G.; Morrow, J. C; Pirkle, J. L.; Tetraethyllead During the DegradaJackson, R. J.; Sampson, E. J.; Miller, tion of Leaded Gasoline Hydrocarbons in Soil," Environ. Toxicol. Chem. D. T.; Caldwell, K. L. "Trace Metals in Urine of United States Residents: 1998, 27(5), 777-782) Reference Range Concentrations," Environ. Res. 1998, 76(1), 53-59) Contaminants Fate of laundry bleach. A study was Modeling conducted to evaluate and understand the fate of adsorbable organic Aquatic residues. Steady-state modhalide formed from the use of els for predicting chemical residues household bleach during laundering in aquatic food webs were comin a septic system. (Braida, W.; Ong, pared, and differences in predictions S. K.; Smith, W L.; McCabe, J. W of bioaccumulation factors were
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