ISSN:0730-7268    

DOI:10.1002/etc.5620150401

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY

摘要:

AbstractThe direct and indirect effects of the herbicide atrazine were assessed at the community level under exposure patterns likely to be experienced by stream organisms in Vermont. Both attached algae and benthic invertebrates were collected from a clean site using artificial substrates and established in recirculating 120–L laboratory microcosms. On day 1 of the 14–d experiment, three of six microcosms were treated with 5 μg/L atrazine. Concentrations were gradually reduced by replacing a portion of the water in the systems over time so that by day 7, atrazine concentrations were only about 1 μg/L. Direct effects of atrazine on algal biomass were assessed by measuring chlorophyllaconcentrations in samples of attached algae. No differences in chlorophyllawere found between treatment and control microcosms. Potential indirect effects of reduced algal food availability on benthic invertebrate communities were assessed by comparing assemblages in treatment and control microcosms using both a functional (feeding) group classification and taxonomic composition. There were no significant differences in the functional or taxonomic composition of the benthic invertebrate communities; however, a greater number of insects emerged from the treatment microcosms early in the experiment compared to controls, suggesting some response to atrazine. Further community‐level testing is needed to more clearly determine if atrazine is affecting stream or

ISSN:0730-7268    

DOI:10.1002/etc.5620150402

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY

摘要:

AbstractPopulations exposed to pesticides may often be divided into subpopulations, where some subpopulations are exposed to pesticides and others are not. We consider three models for such populations. The first is a simple discrete time model with no density‐dependent reproduction. The second is a continuous time model that includes density‐dependence for populations not exposed to pesticides. In both models, populations exposed to pesticides are assumed to decline geometrically (exponentially in the continuous time model). Migration between exposed and safe habitat patches is symmetric, so that all individuals leaving safe patches enter exposed patches and vice versa. The rate is assumed to be the same for both kinds of patches. The conditions for persistence of the population in the landscape are the same for both models. Increasing migration rate between patches decreases the ability of the population to persist. Populations that have low rates of increase in safe habitat patches have greater difficulty persisting than those with high rates of increase in safe patches. The toxicity of the pesticide also affects population persistence. More toxic pesticides that result in higher rates of death and/or lower rates of birth in exposed habitat patches lower the ability of the population to persist in the landscape. We consider an additional set of models of a metapopulations that persist because of a balance between colonization and local extinction. In such systems, pesticides may endanger regional persistence by reducing the pool of sites available for colonization. We conclude with an outline of important future directions for theoretical research intended to elucidate the impact of pesticides on populations spatially complex landsca

ISSN:0730-7268    

DOI:10.1002/etc.5620150403

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY

摘要:

AbstractChemical registrations under FIFRA (Federal Insecticide, Fungicide, and Rodenticide Act) and TSCA (Toxic Substance Control Act) in the United States, and equivalent regulations in Canada and Europe, are driven extensively by risk assessments. Chemicals intended for use as pesticides are evaluated by considering fate and transport, toxicity, and assumed exposure scenarios. For nonpesticide chemicals, very limited testing information is generated to support the risk management decisions. Despite the restricted quantity of information, risk‐based predictions are intended to provide analyses that are adequate to evaluate ecological safety margins. Persistent questions regarding adequacy of protection have dogged risk assessors, regulators, and registrants. From a scientific perspective, risk assessments are essentially complex hypotheses, not conclusive or factual statements. Given the great reliance on extrapolations from individual‐based toxicity (and generally poor exposure characterizations) to statements of community, ecosystem, landscape, regional, and even global levels of organization, it is perhaps remarkable that the system has worked at all. But do we really know if the system works? If we wish to retain a scientific basis in registration, follow‐up work that tests the risk‐prediction hypotheses needs to be done. Properly structured around testable parameters, focused monitoring programs could reduce much of the mystery embodied in current practice. Greater reliance on monitoring data to test risk predictions could reduce the tendency to concatenate uncertainty factors that unnecessarily expand Type II errors. We propose changes in the registration process to address these c

ISSN:0730-7268    

DOI:10.1002/etc.5620150404

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY

摘要:

AbstractThe community conditioning hypothesis is used as a framework in which to place the layers of effects during and after pesticide intoxication. Community conditioning states that information about the history of a system can be and is written at a variety of organismal and ecological levels. This historical component or etiology determines the future dynamics of a system. The storage of information concerning prior stressor events has been observed in a variety of compartments. Fish populations have been observed to have different genetic structures in populations that have been exposed to toxicant stressors. Analysis of biomarker data from field experiments reveals a variety of patterns, some due to the location of the field plots. Treatment groups within a series of microcosm experiments maintain their identities long after the degradation of the toxicant. The dynamics of the treatment groups in multivariate ecological space are characteristic of a particular treatment. Other microcosm systems differentially respond to invasion depending upon the order of the inoculation of the biotic components, even though at the time of the invasion the systems are indistinguishable. A major factor in the uncertainty of pesticide risk assessment will be the unknown etiology of the system of interest.

ISSN:0730-7268    

DOI:10.1002/etc.5620150405

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY

摘要:

AbstractPurple loosestrife (Lythrum salicaria) is an invasive wetland perennial that became established in northeastern North America in the early 1800s. Despite its designation as a noxious weed, its distribution has continued to expand. Treatment with herbicides is the most widely used means of controlling purple loosestrife. This study examined the nontarget effects of two herbicides, Rodeo® and Garlon® 3A, currently used or being considered for use in controlling purple loosestrife in Washington State, respectively. Growth and/or survival of duckweed,Daphnia, and rainbow trout were monitored for at least 24 h following an application of each herbicide. Free‐living water column and benthic invertebrates were monitored 24 h and 7 d post‐spray using activity traps and sediment cores. Neither chemical was associated with significant decreases in survival or growth of the bioassay organisms, with the exception that growth of duckweed was reduced 48 h after exposure to Rodeo. Nor were significant decreases in the abundance of free‐living aquatic invertebrates detected following the herbicide applications. Results suggest that neither herbicide, at the application rates used, poses a hazard to aquatic invertebrates in wetlands in central Washington. However, Rodeo, because it is a broad‐spectrum herbicide, may pose a greater hazard to nontarget aquatic v

ISSN:0730-7268    

DOI:10.1002/etc.5620150406

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY

摘要:

AbstractIn regions of highly diversified agriculture, herbicides used in one field may not be compatible with crops growing in nearby fields. Injury to nontarget crops may occur from drift or localized atmospheric transport of herbicide residues. Pea, bean, and corn seedlings have been used as sentinels to detect atmospheric deposition of trace residues. Seedlings were exposed at various locations throughout south central Washington and exchanged on a weekly basis with a new set of plants. Plants were returned to a lath house and observed over 3 weeks for development of symptoms indicative of probable exposure to four classes of herbicides—sulfonylureas, phenoxyacetates, aminophosphonic acids, and bipyridiliniums. The most frequently observed symptoms on sentinel plants were chlorotic spots on the upper leaf surfaces; such symptoms were created under controlled conditions by exposing plants to aerosols of the sulfonylurea (SU) herbicide chlorsulfuron. For 3 years, the greatest incidence of probable SU symptoms was detected during April; however, occurrence of symptoms was not correlated with periods of maximum use of SU herbicides on wheat in the region. The results suggested a general atmospheric loading of herbicides with occasional deposition, rather than point source drift. Further tests are needed to quantitate the exposures of sentinel plants and determine if chlorotic spots are associated with adverse physiological effect

ISSN:0730-7268    

DOI:10.1002/etc.5620150407

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY

摘要:

AbstractPartitioning of Cd and Cu between geochemical fractions of an a aerobic estuarine sediment was determined after equilibrating fine‐sandy sediment with different combinations of added Cd (0, 2.5, 5 mg/kg) and Cu (0, 12.5, 25 mg/kg). Sediments were placed in aquaria with 20 ppt seawater where bioassay test organisms were exposed for 14 d. At the start and conclusion of the experimental period, sediments were sequentially extracted to determine the elemental content of the exchangeable (EP), easily reducible (ERP), organic‐sulfide (OSP), moderately reducible (MRP), and acid extractable (AEP) phases. Partitioning of the metals in both the native and treated sediments was, for Cd: OSP ≫ ERP>AEP>EP (MRP was below detection) and for Cu: OSP ≫ AEP>ERP>MRP>EP. Cadmium extracted in all phases and Cu in the EP, ERP, and OSP were proportional to the respective treatments. The EP‐Cd, ERP‐Cd, and OSP‐Cd were affected by the Cu treatment and significant interactions occurred between Cd and Cu for the EP‐Cd, ERP‐Cd, OSP‐Cd, EP‐Cu, and ERP‐Cu. Increasing levels of applied Cd and Cu resulted in greater amounts of EP‐Cd and ERP‐Cd, fractions that are the most bioavailable and the most readily available for desorption into the water column. A significant conclusion is that the input of nontoxic metals may affect the geochemical phase distribution, potential bioavailability, and toxicit

ISSN:0730-7268    

DOI:10.1002/etc.5620150408

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY

摘要:

AbstractThe relationship between Cd and Cu distribution in sediment geochemical fractions and their bioavailability was studied. A fine‐sandy textured estuarine sediment was treated with all combinations of 0, 2.5, and 5 mg/kg Cd and 0, 12, and 25 mg/kg Cu using the chloride salts of each metal. Grass shrimp (Palaemonetes pugio), blue mussel (Mytilus edulis), and hard clam (Mercenaria mercenaria) were exposed to the treated sediments in aquaria with 20 ppt artificial seawater for 14 d. Sediments were sequentially extracted before and after organism exposure to determine the exchangeable, easily reducible, organic‐sulfide, moderately reducible, and acid extractable phases. Low mortalities were observed for all organism types and none were attributable to any of the treatments. The Cd and Cu concentrations in the easily reducible and organic‐sulfide phases were found to be significantly related to the bio‐availability of these metals. The most highly significant relationship was established between Cd in the easily reducible phase and body burden of Cd in the blue mussel. Notable interactions were found between Cd and Cu in some of the geochemical phases, body burdens, and respiration rates. Metal uptake, respiration, and interactions were highly dependent on the test species. A significant correlation was found between increased body burden and depressed respiration for Cd but not for Cu. Multiple regression models are used to describe these relationships. It appears that the interactive responses in the organisms are driven primarily by the sediment geochemical effects and mediated by individual organism processes. These results underscore the necessity of multicomponent (multielement) studies in assessing the fate and effects of toxic elements in the envi

ISSN:0730-7268    

DOI:10.1002/etc.5620150409

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY

摘要:

AbstractTriethanolamine production in the United States exceeds 100,000 metric tons per year. Given this magnitude of production and widespread distribution to consumer product, specialty chemical, and agricultural chemical markets, an understanding of the environmental fate and lifetime of this chemical is warranted. Studies were conducted to determine the fate and lifetime of [14C]triethanolamine in an aerobic surface soil, freshwater river systems, and in activated sludge waste treatment. The half‐life determined for biodegradation of triethanolamine ranged from 0.02 to 0.10 d in reactions containing 818 mg/L mixed liquor activated sludge solids from a municipal wastewater treatment facility. The half‐life of triethanolamine in a sandy loam surface soil ranged from 0.5 to 1.8 d for initial concentrations ranging from 0.01 to 13.4 mmol/kg (1.4–2,000 mg/kg dry wt). Biodegradation was also measured in two different river waters, with an average half‐life (±1 SD) of 1.2 ± 0.5 d determined for initial triethanolamine concentrations of 0.67 and 3.28 μmol/L (99 and 489 μg/L). The kinetics of both primary biodegradation and mineralization were shown to be generally first‐order in triethanolamine and biomass concentrations (second‐order overall) for the matrices and range of triethanolamine concentrations tested. When these relatively short half‐lives are related to typical chemical residence times in various environmental compartments, it can be concluded that biodegradation would prevent accumulation of triethanolamine and its associated degradation products i

ISSN:0730-7268    

DOI:10.1002/etc.5620150410

出版商:Wiley Periodicals, Inc.    

年代:1996

数据来源: WILEY