research watch: warming and pollution

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and injection port hardware of commercial bags. The authors re- port that use of Teflon valves in the homemade bags cut losses of VOCs by more than 50%. (Environ. Sci. Technol., 1996, 30, 3115-17) MODELING Warming and pollution Could higher global temperatures associated with global climate change increase the public health risks from pollution? T E. McKone and co-workers examined the ef- fects of regional temperature change on risks associated with re- leases of hexachlorobenzene (HCB), a ubiquitous air, soil, and water pol- lutant. They applied a fugacity model to predict changes in parti- tioning between environmental compartments. It assumed a re- gional environment typical of the western United States, and a global average temperature increase of 5 °C. The increase had little impact on the magnitude of human health risks from HCB released into air or water. Other impacts of climate change, such as precipitation changes and sea level rise, may in- fluence risk assessments for toxic chemicals as well, but these were not addressed. (Risk Analysis 1996, 16(3), 377-93) Forest management Because many goals in forest man- agement are dependent on land- scape features, planners are using spatial analysis as a way to predict the effect of management activities on resources. P. Bettinger and col- leagues report a case study in which they tested the ability of a spatial model, SNAP II+, to evaluate se- lected land management goals in a small Oregon forest watershed. Five scenarios were evaluated for their simultaneous impacts on logging revenue, terrestrial and aquatic habi- tat protection, and other ecosystem values. Model predictions were con- sistent with expectations over the short term: Eliminating harvesting in riparian zones maintained aquatic habitats but reduced revenues. The researchers state that the model shows promise for evaluating man- agement tradeoffs in watershed analysis. (Environ. Manage. 1996, 20(4), 565-77) Mussels as bioindicators of water contamination Marine bivalve molluscs have been used as indicators to assess concentrations of bioavailable contaminants in coastal waters. N. S. Fisher and co-workers used mussels to assess levels of six metals (Ag, Am, Cd, Co, Pb, and Zn). Mussels maintained in the laboratory in running seawater and caged in the field for four months showed similar metal absorption and efflux patterns. Metals accumulated from water generally were bound to the shell, whereas those ingested from food were associated with soft body parts. But different uptake routes were observed: Cd was accumulated from water; Am, Se, and Co from ingested food; and Zn and Ag accumulated significantly via both routes. The authors propose that fecal pel- lets deposited under mussel beds play an important role in biogeochemical cy- cling of metals in coastal ecosystems. (Environ. Sci. Technol., this issue, 3232-42) PESTICIDES Mirex dechlorination Sorption of organic pollutants to hu- mic substances affects the pollut- ant's chemical reactivity. S. B. Burns and colleagues developed a kinetic model that describes the effects of sorption to humic substances on photodechlorination of the pesticide mirex. The rate constant for the mirex reaction increased with the concentration of dissolved organic carbon and reached a limiting value at about 3 mg/L. The model indi- cated that photodechlorination of mirex in humic acid solution was limited to the humic-sorbed phase. Reactivity observed on addition of scavengers confirmed the hypothesis that the dissolved and bound mirex experience different photochemical environments. (Environ. Sci. Tech- nol, 1996, 30, 2934-41) REMEDIATION TCE bioreactor The bacterium Burkholderia (Pseudomonas) cepacia G4 is an im- portant degrader of trichloroethyl- ene (TCE). Degradation of TCE by B. cepacia G4 is a cometabolic event that requires the presence of toluene or other aromatic compounds as a primary substrate. From an engi- neering standpoint, it is desirable to limit the degree of bacterial growth while maintaining high degradation rates to enhance bioreactor perfor- mance. A. E. Mars and colleagues investigated the performance of B. cepacia G4 in the degradation of TCE by using a growth-limited, fed-batch culture and toluene as the growth substrate. Results indicate that this organism could degrade TCE under growth-limited conditions, but high concentrations of TCE led to an in- crease in the concentrations of tolu- ene needed to maintain cometabolic conditions. (Appl. Environ. Microbiol. 1996, 62, 886-91) BTEX biodegradation Groundwater contamination from leaking fuel storage tanks is a world- wide problem. Microorganisms that degrade fuel hydrocarbons offer a promising remediation approach. C-I. Chen and R. T. Taylor studied the degradative activities of two ther- mophilic bacteria in the Thermus spe- cies on nonoxygenated monoaro- matic hydrocarbons, known as BTEX (benzene, toluene, ethylbenzene, xylenes). All BTEX compounds were degraded significantly, by 10-40%. The time-dependent extent of bio- degradation varied with the initial concentration of BTEX Biodegrada- tion increased when the bacteria were pregrown on catechol and o-cresol. Chen and Taylor used labeled sub- strates to show that a fraction of the benzene and toluene was metabolized to C0 2 and water-soluble products. (Biotechnol. Bioeng. 1995, 48, 614-24) Methanol cultures The ability of methanotrophic bacte- ria to rapidly degrade chlorinated solvents has received much recent study. Methanotrophic growth using methane or methane-air mixtures has typically been required for the degradation of trichloroethylene (TCE). M. W. Fitch and colleagues evaluated the ability of a meth- anotroph, Methylosinus trichospo- rium OB3b, strain PP358, to degrade TCE using methanol as the primary growth substrate. The authors inves- tigated the kinetics of TCE degrada- tion under carbon- and oxygen- 4 7 0 A • VOL. 30, NO. 11, 1996/ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS

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Page 1: Research Watch: Warming and pollution

and injection port hardware of commercial bags. The authors re­port that use of Teflon valves in the homemade bags cut losses of VOCs by more than 50%. (Environ. Sci. Technol., 1996, 30, 3115-17)

MODELING Warming and pollution Could higher global temperatures associated with global climate change increase the public health risks from pollution? T E. McKone and co-workers examined the ef­fects of regional temperature change on risks associated with re­leases of hexachlorobenzene (HCB), a ubiquitous air, soil, and water pol­lutant. They applied a fugacity model to predict changes in parti­tioning between environmental compartments. It assumed a re­gional environment typical of the western United States, and a global average temperature increase of 5 °C. The increase had little impact on the magnitude of human health risks from HCB released into air or water. Other impacts of climate change, such as precipitation changes and sea level rise, may in­fluence risk assessments for toxic chemicals as well, but these were not addressed. (Risk Analysis 1996, 16(3), 377-93)

Forest management Because many goals in forest man­agement are dependent on land­scape features, planners are using spatial analysis as a way to predict the effect of management activities on resources. P. Bettinger and col­leagues report a case study in which they tested the ability of a spatial model, SNAP II+, to evaluate se­lected land management goals in a small Oregon forest watershed. Five scenarios were evaluated for their simultaneous impacts on logging revenue, terrestrial and aquatic habi­tat protection, and other ecosystem values. Model predictions were con­sistent with expectations over the short term: Eliminating harvesting in riparian zones maintained aquatic habitats but reduced revenues. The researchers state that the model shows promise for evaluating man­agement tradeoffs in watershed analysis. (Environ. Manage. 1996, 20(4), 565-77)

Mussels as bioindicators of water contamination Marine bivalve molluscs have been used as indicators to assess concentrations of bioavailable contaminants in coastal waters. N. S. Fisher and co-workers used mussels to assess levels of six metals (Ag, Am, Cd, Co, Pb, and Zn). Mussels maintained in the laboratory in running seawater and caged in the field for four months showed similar metal absorption and efflux patterns. Metals accumulated from water generally were bound to the shell, whereas those ingested from food were associated with soft body parts. But different uptake routes were observed: Cd was accumulated from water; Am, Se, and Co from ingested food; and Zn and Ag accumulated significantly via both routes. The authors propose that fecal pel­lets deposited under mussel beds play an important role in biogeochemical cy­cling of metals in coastal ecosystems. (Environ. Sci. Technol., this issue, 3232-42)

PESTICIDES Mirex dechlorination Sorption of organic pollutants to hu-mic substances affects the pollut­ant's chemical reactivity. S. B. Burns and colleagues developed a kinetic model that describes the effects of sorption to humic substances on photodechlorination of the pesticide mirex. The rate constant for the mirex reaction increased with the concentration of dissolved organic carbon and reached a limiting value at about 3 mg/L. The model indi­cated that photodechlorination of mirex in humic acid solution was limited to the humic-sorbed phase. Reactivity observed on addition of scavengers confirmed the hypothesis that the dissolved and bound mirex experience different photochemical environments. (Environ. Sci. Tech­nol, 1996, 30, 2934-41)

REMEDIATION

TCE bioreactor The bacterium Burkholderia (Pseudomonas) cepacia G4 is an im­portant degrader of trichloroethyl-ene (TCE). Degradation of TCE by B. cepacia G4 is a cometabolic event that requires the presence of toluene or other aromatic compounds as a primary substrate. From an engi­neering standpoint, it is desirable to limit the degree of bacterial growth while maintaining high degradation rates to enhance bioreactor perfor­mance. A. E. Mars and colleagues investigated the performance of B. cepacia G4 in the degradation of TCE by using a growth-limited, fed-batch culture and toluene as the growth substrate. Results indicate that this

organism could degrade TCE under growth-limited conditions, but high concentrations of TCE led to an in­crease in the concentrations of tolu­ene needed to maintain cometabolic conditions. (Appl. Environ. Microbiol. 1996, 62, 886-91)

BTEX biodegradation Groundwater contamination from leaking fuel storage tanks is a world­wide problem. Microorganisms that degrade fuel hydrocarbons offer a promising remediation approach. C-I. Chen and R. T. Taylor studied the degradative activities of two ther­mophilic bacteria in the Thermus spe­cies on nonoxygenated monoaro-matic hydrocarbons, known as BTEX (benzene, toluene, ethylbenzene, xylenes). All BTEX compounds were degraded significantly, by 10-40%. The time-dependent extent of bio­degradation varied with the initial concentration of BTEX Biodegrada­tion increased when the bacteria were pregrown on catechol and o-cresol. Chen and Taylor used labeled sub­strates to show that a fraction of the benzene and toluene was metabolized to C02 and water-soluble products. (Biotechnol. Bioeng. 1995, 48, 614-24)

Methanol cultures The ability of methanotrophic bacte­ria to rapidly degrade chlorinated solvents has received much recent study. Methanotrophic growth using methane or methane-air mixtures has typically been required for the degradation of trichloroethylene (TCE). M. W. Fitch and colleagues evaluated the ability of a meth-anotroph, Methylosinus trichospo-rium OB3b, strain PP358, to degrade TCE using methanol as the primary growth substrate. The authors inves­tigated the kinetics of TCE degrada­tion under carbon- and oxygen-

4 7 0 A • VOL. 30, NO. 11, 1996/ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS