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Environmental Scientists (environmental + scientists)
Selected AbstractsNanomaterials in the environment: Behavior, fate, bioavailability, and effects,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2008Stephen J. Klaine Abstract The recent advances in nanotechnology and the corresponding increase in the use of nanomaterials in products in every sector of society have resulted in uncertainties regarding environmental impacts. The objectives of this review are to introduce the key aspects pertaining to nanomaterials in the environment and to discuss what is known concerning their fate, behavior, disposition, and toxicity, with a particular focus on those that make up manufactured nanomaterials. This review critiques existing nanomaterial research in freshwater, marine, and soil environments. It illustrates the paucity of existing research and demonstrates the need for additional research. Environmental scientists are encouraged to base this research on existing studies on colloidal behavior and toxicology. The need for standard reference and testing materials as well as methodology for suspension preparation and testing is also discussed. [source] Why environmental scientists are becoming BayesiansECOLOGY LETTERS, Issue 1 2005James S. Clark Abstract Advances in computational statistics provide a general framework for the high-dimensional models typically needed for ecological inference and prediction. Hierarchical Bayes (HB) represents a modelling structure with capacity to exploit diverse sources of information, to accommodate influences that are unknown (or unknowable), and to draw inference on large numbers of latent variables and parameters that describe complex relationships. Here I summarize the structure of HB and provide examples for common spatiotemporal problems. The flexible framework means that parameters, variables and latent variables can represent broader classes of model elements than are treated in traditional models. Inference and prediction depend on two types of stochasticity, including (1) uncertainty, which describes our knowledge of fixed quantities, it applies to all ,unobservables' (latent variables and parameters), and it declines asymptotically with sample size, and (2) variability, which applies to fluctuations that are not explained by deterministic processes and does not decline asymptotically with sample size. Examples demonstrate how different sources of stochasticity impact inference and prediction and how allowance for stochastic influences can guide research. [source] Acute and chronic toxicity of five selective serotonin reuptake inhibitors in Ceriodaphnia dubiaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2004Theodore B. Henry Abstract Contamination of surface waters by pharmaceutical chemicals has raised concern among environmental scientists because of the potential for negative effects on aquatic organisms. Of particular importance are pharmaceutical compounds that affect the nervous or endocrine systems because effects on aquatic organisms are possible at low environmental concentrations. Selective serotonin reuptake inhibitors (SSRIs) are drugs used to treat clinical depression in humans, and have been detected in low concentrations in surface waters. In this investigation, the acute and chronic toxicity of five SSRIs (fluoxetine, Prozac®; fluvoxamine, Luvox®; paroxetine, Paxil®; citalopram, Celexa®; and sertraline, Zoloft®) were evaluated in the daphnid Ceriodaphnia dubia. For each SSRI, the 48-h median lethal concentration (LC50) was determined in three static tests with neonate C. dubia, and chronic (8-d) tests were conducted to determine no-observable-effect concentrations (NOEC) and lowest-observable-effect concentrations (LOEC) for reproduction endpoints. The 48-h LC50 for the SSRIs ranged from 0.12 to 3.90 mg/L and the order of toxicity of the compounds was (lowest to highest): Citalopram, fluvoxamine, paroxetine, fluoxetine, sertraline. Mortality data for the 8-d chronic tests were similar to the 48-h acute data. The SSRIs negatively affected C. dubia reproduction by reducing the number of neonates per female, and for some SSRIs, by reducing the number of broods per female. For sertraline, the most toxic SSRI, the LOEC for the number of neonates per female was 0.045 mg/L and the NOEC was 0.009 mg/L. Results indicate that SSRIs can impact survival and reproduction of C. dubia; however, only at concentrations that are considerably higher than those expected in the environment. [source] Living under an atomic force microscopeGEOBIOLOGY, Issue 3 2005An optimized approach for in vivo investigations on surface alterations towards biomineral nucleation on cyanobacterial cells ABSTRACT An approach for long-term in vivo investigations on cyanobacterial cell surface changes at high spatial resolution by Atomic Force Microscopy (AFM) was developed in this study. Until recently, changes of bacterial cell surfaces due to changes of the chemical environment could neither be investigated in situ nor in vivo. However, in vivo investigations give insights into kinetics of cell response to environmental changes and mineral nucleation at the cell's surface. Continuously cultured cyanobacteria of the representative freshwater strain Synechococcus leopoliensis (PCC 7942) were washed and artificially immobilized on poly-l-lysine-coated glass slides. Both immobilization and environmental conditions were optimized in order to facilitate long-term experiments (> 100 h) with living cells. AFM samples were investigated in situ in two different solutions: Culture medium was used for cultivation experiments and nutrient-free NaHCO3/CaCl2 solutions (supersaturated with respect to calcite) for long-term characterizations of the changes in cell surface topography. Cell viability under these conditions was investigated by AFM, TEM and epifluorescence microscopy, independently. No indications for extended starvation were found within the relevant timescales. Analysing the influence of Ca2+ on the surface of S. leopoliensis, we found significant changes compared to a Ca-free solution. Few hours after CaCl2 was added to the circumfluent solution, small protuberances were observed on the cell surface. These are promising results to environmental scientists for a wide range of applications, as cell response to environmental changes can now be monitored online and in vivo at timescales, which are relevant for natural processes. Most especially studies of biomineralization and mineral nucleation on bacterial cell surfaces will profit from this new approach. [source] The Local Shape of Revolution: Reflections on Quantitative Geography at Cambridge in the 1950s and 1960sGEOGRAPHICAL ANALYSIS, Issue 3 2008Peter Haggett The "quantitative revolution" in human geography which swept across so many universities in the 1950s and 1960s had its main diffusion centers in a few locations which were to have global significance. Two critical early centers were the University of Washington in the Pacific Northwest and Lund University in southern Sweden. But the experience of change was different in different locations as the general forces of perturbation sweeping around academia were translated into local eddies with local repercussions. Here, small and somewhat random quirks at the outset, led eventually to fundamental divergences between adoption and rejection. The theme is illustrated by reference to changes which occurred at Cambridge, one of England's two oldest universities, as seen from the perspective of someone who,as undergraduate, graduate student, and later, faculty member,was caught up in these changes and took some small part in propagating them. Special attention is given to the role of two environmental scientists, Vaughan Lewis and Richard Chorley, in introducing changes and the way in which later developments in human geography drew on preceding experiences in physical geography. The reasons behind the "Cambridge variant" and the questions of how intellectual DNA is passed across the generations are discussed. [source] Ideas and Environmental Standard-Setting: A Comparative Study of Regulation of the Pulp and Paper IndustryGOVERNANCE, Issue 1 2002Kathryn Harrison This article examines the policy responses of Canada, Sweden, and the United States to the discovery of dioxins in pulp mill effluents and paper products, with particular attention to the impact of science and the scientific community on national environmental standards. Important areas of policy divergence were found, despite considerable scientific consensus among environmental scientists in the three jurisdictions, as the potential force of shared causal knowledge was undermined by competing domestic interests and different institutional contexts for decision-making. This analysis challenges the emphasis of the epistemic community literature on the role of scientists in promoting policy convergence, underscoring the importance of the interaction of ideas, interest group politics, and institutions in public policy-making. [source] Interacting effects of management and environmental variability at multiple scales on invasive species distributionsJOURNAL OF APPLIED ECOLOGY, Issue 6 2009Jeffrey M. Diez Summary 1. The distribution and abundance of invasive species can be driven by both environmental variables and land management decisions. However, understanding these relationships can be complicated by interactions between management actions and environmental variability, and differences in scale among these variables. The resulting ,context-dependence' of management actions may be well-appreciated by ecologists and land managers, but can frustrate attempts to apply general management principles. 2. In this study, we quantify the effects of land management and environmental variability at different scales on the occurrence and abundance of Hieracium pilosella, a major agricultural weed in New Zealand. We used a hierarchical study design and analysis to capture relevant scales of variation in management actions and environmental heterogeneity, and test hypotheses about how these factors interact. 3. We show that fertilizing and grazing interact with environmental gradients at the scale of management application (farm paddocks) to influence the establishment and local abundance of H. pilosella. 4. We further show that H. pilosella's relationships with fine-scale abiotic and biotic factors are consistent with expected mechanisms driven by larger-scale management actions. Using data on occurrence and local abundance, we tease apart which factors are important to establishment and subsequent local spread. 5.Synthesis and applications. A major challenge for environmental scientists is to predict how invasive species may respond to ongoing landscape modifications and environmental change. This effort will require approaches to study design and analysis that can accommodate complexities such as interacting management and environmental variables at different scales. Management actions will be more likely to succeed when they explicitly account for variation in environmental context. [source] Pesticide soil sorption parameters: theory, measurement, uses, limitations and reliability,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 5 2002R Don Wauchope Abstract The soil sorption coefficient Kd and the soil organic carbon sorption coefficient KOC of pesticides are basic parameters used by environmental scientists and regulatory agencies worldwide in describing the environmental fate and behavior of pesticides. They are a measure of the strength of sorption of pesticides to soils and other geosorbent surfaces at the water/solid interface, and are thus directly related to both environmental mobility and persistence. KOC is regarded as a ,universal' parameter related to the hydrophobicity of the pesticide molecule, which applies to a given pesticide in all soils. This assumption is known to be inexact, but it is used in this way in modeling and estimating risk for pesticide leaching and runoff. In this report we examine the theory, uses, measurement or estimation, limitations and reliability of these parameters and provide some ,rules of thumb' for the use of these parameters in describing the behavior and fate of pesticides in the environment, especially in analysis by modeling. © 2002 Society of Chemical Industry [source] | |||||||||||||