摘要:

AbstractBiodegradation processes for pentachlorophenol (PCP) and a commercial PCP formulation were evaluated to delineate factors limiting the rate of PCP degradation in the aquatic environment. Analyses of the data on PCP disappearance and chloride ion release, as well as gas chromatography and UV‐VIS (ultra‐violet and visible spectroscopy) spectra of the fermentor broth strongly indicate that the bacterial culture acted on PCP by completely stripping off all the chloride ions from a molecule of PCP, rather than following the normal pattern of removing only one chloride ion at a time. The haloaromatic ring structure of PCP was completely broken down, and not channeled into the unproductive meta‐cleavage pathway. Despite repeated transfers of the bacterial culture, an initial lag phase in PCP biodegradation was apparent in all experiments and was followed by a steady state, nearly linear rate of PCP degradation. Thus in the aquatic environment the biodegradation rate of a persistent contaminant is more likely to be regulated by whether or not this compartment has been previously subjected to a long or continuous exposure to a particular chemical. First‐order kinetics alone cannot be used to predict accurately the fate of a persistent chemical in the environment, because of the inability of such a simple equation to accommodate the effects of rate‐limiting factors such as the length of adaptation period on the overall biodegradation rate of a contaminant. For this reason, factors that may influence a chemical's biodegradability in the natural environment must be considered in the design of laboratory biodegradation ex

ISSN:0884-8181    

DOI:10.1002/tox.2540040202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractMicrocosm and mesocosm experiments are useful in the environmental analysis of the effects of toxicants on ecological communities. While there has been much interest in the biological approaches to microcosm design, there seems to have been little thought given to statistical issues in the design of these experiments. Here, some statistical design issues are considered. Some criteria are proposed, and optimal or near optimal designs suggested. Of particular interest is the choice of doses in the experiment, choices that allow for tests with high power and also provide good estimates of effect levels and other parameters. Also, some analytical techniques recently suggested for the analysis of community data are criticized and alternate methods suggested.

ISSN:0884-8181    

DOI:10.1002/tox.2540040203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA survey of sediment microbial activity and toxicity toDaphnia magna, Ceriodaphnia dubia, andSelenastrum capricornutumwas conducted on two streams receiving numerous effluents in Ohio—the Little Scioto River and Dick's Creek. Microbial activity assays included alkaline phosphatase, dehydrogenase, β‐galactosidase, β‐glucosidase. Activity was compared to overlying water chemistry and revealed several statistically significant correlations. No macrofaunal assay toxicity was observed in Dick's Creek. Sediment toxicity was found at two stations in the Little Scioto River, and varied in degree and organism sensitivity with time of sampling. These results support earlier studies suggesting the need for multiple trophic‐level assays in aquatic ecosystem evaluations of toxican

ISSN:0884-8181    

DOI:10.1002/tox.2540040204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractEcologically realistic laboratory and field simulated ecosystems (microcosms and mesocosms) are playing increasing roles in fate and effect testing of chemicals and mixtures. Controlled ecosystems allow evaluation of toxicant effects on collective and emergent ecosystem properties. Information is needed to evaluate the validity of test system responses, interpretability of results, and cost effectiveness of simulated ecosystem tests. We developed replicate microcosms using periphyton on polyurethane artificial substrates. Source communities were obtained from two ecosystems—a reservoir in Kentucky and a softwater pond in Virginia—and tested for effects of continuous inputs of phenol (up to 30 mg/L) over 21 days. System responses measured included several biomass estimators, net oxygen production, and protozoan species richness. Communities were generally insensitive to phenol input. Primary production in microcosms from both ecosystems was inhibited at phenol concentrations>10 mg/L and chlorophyll a concentrations were also depressed. Other biomass estimators (protein, hexosamine) were not affected or were stimulated at lower (⩽10 mg/L) phenol concentrations. Protozoan species numbers were not affected. Functional shifts in the communities preceded adverse structural effects. Effect levels were similar for both communities, although the more complex community with greater biomass (Kentucky) showed more significant responses than the simpler community (Virginia). Systems showed resistance to phenol levels that were actually toxic in standard single‐species tests, suggesting that ecosystems may differ in magnitude and rate of response to some nonpersistent to

ISSN:0884-8181    

DOI:10.1002/tox.2540040205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe public water supply has been implicated in gastrointestinal disorders in the United States, East Africa, and Australia, associated with the lysis of heavy blooms of cyanobacteria. The causative organisms includeMicrocystis, Anabaena, Aphanizomenon, andOscillatoria. Using epidemiological techniques, we have shown significant increase in liver enzymes in blood, particularly γ‐glutamyl transpeptidase, during a toxic bloom in the reservoir of a city. Therefore, public health awareness of the risks, and consequent action to control water blooms and remove harmful compounds from drinking water supplies, is requir

ISSN:0884-8181    

DOI:10.1002/tox.2540040206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractOxygen uptake coupled with nitrite oxidation by washed cell suspensions ofNitrobacter agiliswas tested in the presence of copper, nickel, aluminum, uranyl, and molybdate ions. Copper ion was slightly stimulatory at low concentrations and strongly inhibitory at 17 mM. Molybdate ion showed either slight enhancement or no inhibition at all test concentrations. With the other test ions, inhibition of oxygen uptake was observed. Carbon dioxide fixation was generally more sensitive to metal ions than was oxygen uptake. Cytochrome reduction in washed cells ofN. agiliswas demonstrated in the presence and absence of metal ions. Cytochromeaa3and cytochromea1(α‐peak at 590 nm) were sensitive to aluminum, uranyl, and molybdate ions, whereas cytochromec(β‐peak at 520 nm) was insensitive to test ions. All metal ions inhibited the reduction of cytochromea1(γ‐peak at 438 nm). This inhibition decreased when the concentration of copper and molybdate was increased to 1.7 mM. Only aluminum and nickel ions demonstrated a concentration‐dependent inhibition of cytochromea1(438 nm). The test ions blocked the activity of cytochromec(α‐peak at 550 nm). The inhibition of cytochromecat 415 nm (γ‐peak) w

ISSN:0884-8181    

DOI:10.1002/tox.2540040207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractOxygen uptake coupled with nitrite oxidation by washed cell suspensions was not influenced by persulfate or tetrathionate. Carbon dioxide fixation was insensitive to tetrathionate, and in fact, an enhancement by tetrathionate was observed. Persulfate inhibited the fixation of carbon dioxide only at a high concentration (17 mMS2O2−8). Cytochrome reduction in washed cells ofNitrobacter agiliswas demonstrated in the presence and absence of sulfooxyanions. Cytochromeaa3and cytochromea1(α‐peak at 590 nm) were sensitive to sulfooxyanions (sulfite, thiosulfate, metabisulfite, dithionate, persulfate, trithionate, and tetrathionate), whereas cytochromec(β‐peak at 520 nm) was insensitive to test ions. All sulfooxyanions inhibited the reduction of cytochromea1(γ‐peak at 438 nm). This inhibition decreased when the concentration of sulfooxyanions was increased to 17 mM. The reduction of cytochromecat 550 nm (α‐peak) was blocked by the test ions and the inhibition of cytochromecat 415 nm (γ‐peak) was also apparent. Complete inhibition of cytochromec(γ‐peak) was observed in the presence

ISSN:0884-8181    

DOI:10.1002/tox.2540040208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractProtozoan communities developed on artificial substrates were used in a series ofin situand laboratory tests to evaluate the toxic potential of harbor sediments contaminated with polychlorinated biphenyl (PCB). Colonization dynamics in polluted and clean harbors were compared. Laboratory tests were community bioassays using standard techniques to produce sediment elutriate. Results of thein situcolonization and the community tests measuring structural changes (e.g., “decolonization”) were similar. In general, sediments from the contaminated harbor caused significant (p⩽ 0.05) reductions in the number of taxa, in total protozoan abundance, and in phototroph abundance; however, the abundance of heterotrophic species increased in somein situtests. Process‐level parameters (e.g., respiration; island‐epicenter colonization rates) were more sensitive than measurements of community structure. Phototrophs were more sensitive to sediment elutriate than were other trophic types. The information provided by this series of protozoan community tests is more complex than that provided by single‐species bioassays. Although community tests may provide more information on the effects of sediment contamination on actual ecosystems than tests based on single species, they require careful interpretation to avoid misleading

ISSN:0884-8181    

DOI:10.1002/tox.2540040209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0884-8181    

DOI:10.1002/tox.2540040201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY