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1.
Mark A. Engle Michael T. Tate David P. Krabbenhoft Allan Kolker Mark L. Olson Eric S. Edgerton John F. DeWild Ann K. McPherson 《Applied Geochemistry》2008
Concentrations of atmospheric Hg species, elemental Hg (Hg°), reactive gaseous Hg (RGM), and fine particulate Hg (Hg-PM2.5) were measured at a coastal site near Weeks Bay, Alabama from April to August, 2005 and January to May, 2006. Mean concentrations of the species were 1.6 ± 0.3 ng m−3, 4.0 ± 7.5 pg m−3 and 2.7 ± 3.4 pg m−3, respectively. A strong diel pattern was observed for RGM (midday maximum concentrations were up to 92.7 pg m−3), but not for Hg° or Hg-PM2.5. Elevated RGM concentrations (>25 pg m−3) in April and May of 2005 correlated with elevated average daytime O3 concentrations (>55 ppbv) and high light intensity (>500 W m−2). These conditions generally corresponded with mixed continental-Gulf and exclusively continental air mass trajectories. Generally lower, but still elevated, RGM peaks observed in August, 2005 and January–March, 2006 correlated significantly (p < 0.05) with peaks in SO2 concentration and corresponded to periods of high light intensity and lower average daytime O3 concentrations. During these times air masses were dominated by trajectories that originated over the continent. Elevated RGM concentrations likely resulted from photochemical oxidation of Hg° by atmospheric oxidants. This process may have been enhanced in and by the near-shore environment relative to inland sites. The marine boundary layer itself was not found to be a significant source of RGM. 相似文献
2.
Mark A. Engle Fraser Goff David G. Jewett Gregory J. Reller Joel B. Bauman 《Hydrogeology Journal》2008,16(3):559-573
Boron, chloride, sulfate, δD, δ18O, and 3H concentrations in surface water and groundwater samples from the Sulphur Bank Mercury Mine (SBMM), California, USA were
used to examine geochemical processes and provide constraints on evaporation and groundwater flow. SBMM is an abandoned sulfur
and mercury mine with an underlying hydrothermal system, adjacent to Clear Lake, California. Results for non-3H tracers (i.e., boron, chloride, sulfate, δD, and δ18O) identify contributions from six water types at SBMM. Processes including evaporation, mixing, hydrothermal water input
and possible isotopic exchange with hydrothermal gases are also discerned. Tritium data indicate that hydrothermal waters
and other deep groundwaters are likely pre-bomb (before ~1952) in age while most other waters were recharged after ~1990.
A boron-based steady-state reservoir model of the Herman Impoundment pit lake indicates that 71–79% of its input is from meteoric
water with the remainder from hydrothermal contributions. Results for groundwater samples from six shallow wells over a 6–month
period for δD and δ18O suggests that water from Herman Impoundment is diluted another 3% to more than 40% by infiltrating meteoric water, as it
leaves the site. Results for this investigation show that environmental tracers are an effective tool to understand the SBMM
hydrogeologic regime.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Résumé Les concentrations en bore, chlorure, sulfate, δD, δ18O, et 3H d’échantillons d’eaux de surface et souterraine prélevés dans le banc de soufre de la mine de mercure (SBMM en anglais) en Californie, USA, ont été utilisées pour étudier les processus géochimiques et pour fournir des contraintes à l’évaporation et à l’écoulement des eaux souterraines. La SBMM est une mine de soufre et de mercure abandonnée, adjacente au lac Clear en Californie et sous laquelle se trouve un système hydrothermal.Les résultats des traceurs autres que le tritium (bore, chlorure, sulfate, δD, et δ18O) ont permis d’identifier des contributions de six types d’eaux à SBMM. Des processus tels que l’évaporation, le mélange, l’entrée d’eau hydrothermale et de possibles échanges isotopiques avec des gaz hydrothermaux ont également été identifiés. Les données de tritium montrent que les eaux hydrothermales et d’autres eaux profondes sont probablement d’age antérieure à la bombe (avant ~1952), alors que la plupart des autres eaux sont issues de la recharge après ~1990. Un modèle de réservoir représentant le lac situé dans la partie Herman Impoundment de l’ancienne mine, en régime permanent et basé sur le bore, montre que 71–79% de l’eau provient des précipitations, le reste provenant de contributions hydrothermales. Les résultats de δD et δ18O pour des échantillons d’eau souterraine de six puits peu profonds sur une période de 6 mois suggèrent que l’eau de Hermann Impoundment est encore diluée entre 3% jusqu’à plus de 40% lorsqu’elle quitte le site du fait de l’infiltration d’eau météorique. Les résultats de cette étude montrent que les traceurs environnementaux constituent un outil efficace pour comprendre le régime hydrogéologique de la SBMM.
Resumen Se han utilizado datos de concentraciones de boro, cloruros, sulfatos, δD, δ18O, y 3H en muestras de aguas superficiales y subterráneas procedentes de la Mina de Mercurio Sulphur Bank (SBMM), California, USA, para estudiar los procesos geoquímicos y caracterizar la evaporación y el flujo del agua subterránea. SBMM es una mina abandonada de azufre y mercurio con un sistema hidrotermal subyacente, cercano al Lago Clear, California.Los resultados de los trazadores que no son 3H (por ejemplo, boro, cloruros, sulfatos δD, y δ18O) identifican las contribuciones de seis tipos de agua en la SBMM. Se han identificado diversos procesos, como evaporación, mezcla, entrada de agua hidrotermal y la posibilidad de intercambios isotópicos con gases hidrotermales. Los datos de tritio indican que las aguas hidrotermales y otras aguas subterráneas profundas son probablemente pre-bombas (previas a ~1952) en edad mientras que la mayoría de las otras aguas se han recargado después de ~1990. Un modelo estacionario basado en el boro de la fosa del lago Herman Impoundment indica que el 71–79% de su entrada procede de agua meteórica con restos de contribución hidrotermal. Los resultados para las muestras de aguas subterráneas procedentes de seis pozos superficiales en un periodo de 6 meses para δD y δ18O sugieren que el agua procedente de Herman Impoundment se diluye en otro 3% hasta más del 40% debido a la infiltración de agua meteórica., que sale del sitio. Los resultados de esta investigación muestran que los trazadores ambientales son una herramienta efectiva para entender el régimen hidrogeológico de la SBMM.相似文献
3.
J. C. Kurtz N. D. Detenbeck V. D. Engle K. Ho L. M. Smith S. J. Jordan D. Campbell 《Estuaries and Coasts》2006,29(1):107-123
Coastal ecosystems are ecologically and commercially valuable, productive habitats that are experiencing escalating compromises
of their structural and functional integrity. The Clean Water Act (USC 1972) requires identification of impaired water bodies
and determination of the causes of impairment. Classification simplifies these determinations, because estuaries within a
class are more likely to respond similarly to particular stressors. We reviewed existing classification systems for their
applicability to grouping coastal marine and Great Lakes water bodies based on their responses to aquatic stressors, including
nutrients, toxic substances, suspended sediments, habitat alteration, and combinations of stressors. Classification research
historically addressed terrestrial and freshwater habitats rather than coastal habitats. Few efforts focused on stressor response,
although many well-researched classification frameworks provide information pertinent to stressor response. Early coastal
classifications relied on physical and hydrological properties, including geomorphology, general circulation patterns, and
salinity. More recent classifications sort ecosystems into a few broad types and may integrate physical and biological factors.
Among current efforts are those designed for conservation of sensitive habitats based on ecological processes that support
patterns of biological diversity. Physical factors, including freshwater inflow, residence time, and flushing rates, affect
sensitivity to stressors. Biological factors, such as primary production, grazing rates, and mineral cycling, also need to
be considered in classification. We evaluate each existing classification system with respect to objectives, defining factors,
extent of spatial and temporal applicability, existing sources of data, and relevance to aquatic stressors. We also consider
classification methods in a generic sense and discuss their strengths and weaknesses for our purposes. Although few existing
classifications are based on responses to stressors, may well-researched paradigms provide important information for improving
our capabilities for classification, as an investigative and predictive management tool. 相似文献
4.
Alteration of hydrological processes and streamflow with juniper (Juniperus virginiana) encroachment in a mesic grassland catchment 
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下载免费PDF全文 Chris B. Zou Donald J. Turton Rodney E. Will David M. Engle Sam D. Fuhlendorf 《水文研究》2014,28(26):6173-6182
To understand the effect of woody plant encroachment on hydrological processes of mesic grasslands, we quantified infiltration capacity in situ, the temporal changes in soil water storage, and streamflow of a grassland catchment and a catchment heavily encroached by juniper (Juniperus virginiana, eastern redcedar) in previously cultivated, non‐karst substrate grasslands in north‐central Oklahoma for 3 years. The initial and steady‐state infiltration rates under the juniper canopy were nearly triple to that of the grassland catchment and were intermediate in the intercanopy spaces within the encroached catchment. Soil water content and soil water storage on the encroached catchment were generally lower than on the grassland catchment, especially when preceding the seasons of peak rainfall in spring and fall. Frequency and magnitude of streamflow events were reduced in the encroached catchment. Annual runoff coefficients for the encroached catchment averaged 2.1%, in contrast to 10.6% for the grassland catchment. Annual streamflow duration ranged from 80 to 250 h for the encroached catchment compared with 600 to 800 h for the grassland catchment. Our results showed that the encroachment of juniper into previously cultivated mesic grasslands fundamentally alters catchment hydrological function. Rapid transformation of mesic grassland to a woodland state with juniper encroachment, if not confined, has the potential to drastically reduce soil water, streamflow and flow duration of ephemeral streams in the Southern Great Plains. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
Unpacking governance: Building adaptive capacity to climate change of river basins in Brazil 总被引：1，自引：0，他引：1
Governance and institutions are critical determinants of adaptive capacity and resilience. Yet the make-up and relationships between governance components and mechanisms that may or may not contribute to adaptive capacity remain relatively unexplored empirically. This paper builds on previous research focusing on integrated water resources management in Brazil to ‘unpack’ water governance mechanisms that may shape the adaptive capacity of water systems to climatic change. We construct a river basin index to characterize governance approaches in 18 Brazilian river basins, apply a reliability test to assess the validity of these governance indicators, and use in-depth qualitative data collected in a subsample of the basins to explore the relationship between the governance indicators and adaptive capacity. The analysis suggests a positive relationship between integrated water governance mechanisms and adaptive capacity. In addition, we carry out a cluster analysis to group the basins into types of governance approaches and further unveil potential relationships between the governance variables and overall adaptive capacities. The cluster analysis indicates that tensions and tradeoffs may exist between some of the variables, especially with equality of decision making and knowledge availability; a finding that has implications for decision makers aiming to build adaptive capacity and resilience through governance and institutional means. 相似文献
6.
Late Pliocene Procynocephalus subhimalayanus from the Upper Siwaliks, India is known from only three specimens. The dietary proclivities of this taxon have implications for reconstructing the paleoecology of the Upper Siwaliks. The dental microwear texture properties of Procynocephalus are compared to those from extant tropical forest primates including Alouatta palliata (n = 11), Cebus apella (n = 13), Gorilla gorilla (n = 9), Lophocebus albigena (n = 15) and Trachypithecus cristatus (n = 12). Dental microwear textures are generated by scanning the surface enamel of Facet 9 using white-light confocal microscopy at 100x. Four variables were extracted from scale-sensitive fractal analysis, and the data were ranked before ANOVA with post-hoc tests of significance and multivariate analyses were performed. Procynocephalus clusters closest to Lophocebus, Cebus and some Gorilla specimens suggesting hard-object feeding characterized a portion of its diet. The dental microwear texture of Procynocephalus supports interpretations of widespread grasslands of the Late Pliocene Kansal Formation (Pinjor zone). The extreme enamel complexity characterizing Procynocephalus may derive from consumption of underground storage organs, or other foods with high grit loads. Foods consumed near ground level carry a heavy load of abrasive minerals possibly contributing to greater enamel surface complexity and textural fill volume. 相似文献
7.
Amongst the techniques discussed are (a) for univariate series, generalisations of Box-Jenkins auto-regressive-moving average models including intervention analysis, non-linear models, and models with time varying parameters; (b) for single output, multiple input situations, causality testing, and diagnostic testing of alternative specifications using Lagrange multiplier tests; and (c) for multivariate cases, vector autoregressive models, order-selection criteria, Bayesian priors, and factor models. Co-integration and error-correction models are also introduced.Some of these techniques are illustrated using a forecast comparison exercise concerning forecasts of monthly electricity demand per customer. 相似文献
8.
Refinement, validation, and application of a benthic condition index for Northern Gulf of Mexico estuaries 总被引：1，自引：0，他引：1
By applying discriminant analysis to benthic macroinvertebrate data, we have developed an indicator of benthic condition for northern Gulf of Mexico estuaries. The data used were collected by the United states Environmental Protection Agency’s Environmental Monitoring and Assessment Program (EMAP) in the Louisianian Province from 1991 to 1994. This benthic index represents a linear combination of the following weighted parameters: the proportion of expected species diversity, the mean abundance of tubificid oligochaetes, the percent of total abundance represented by capitellid polychaetes, the percent of total abundance represented by bivalve mollusks, and the percent of total abundance represented by amphipods. We successfully validated and retrospectively applied the benthic index to all of the benthic data collected by EMAP in the Louisianian Province. This benthic index was also calculated for independent data collected from Pensacola Bay, Florida, in order to demonstrate its flexibility and applicability to different estuarine systems within the same biogeographic region. The benthic index is a useful and valid indicator of estuarine condition that is intended to provide environmental managers with a simple tool for assessing the health of benthic macroinvertebrate communities. 相似文献
9.
In this paper we discuss some of the new and exciting developments in the study of binary stars. Recent technological advances (such as CCDs) now make it possible (even easy) to study faint, astrophysically important binaries that in the past could only be done with large 4 + meter class telescopes. Also, the panoramic nature of CCDs (and the use of mosaics), permit large numbers of stars to be imaged and studied. At this conference, most of the observational material discussed was secured typically with smaller aperture 0.5 – 2 m telescopes. Excellent examples are the discovery of over 104 new ～13 – 20 mag eclipsing (and interacting) binaries now found in nearby galaxies from the EROS, OGLE, MACHO and DIRECT programs. As briefly discussed here, and in more detail in several papers in this volume, a small fraction of these extragalactic eclipsing binaries are now serving as “standard candles” to secure accurate distances to the Magellanic Clouds, as well as to M31 and M33. Moreover, the discovery of increasingly larger numbers of eclipsing binaries has stimulated the development of automatic methods for reducing and analyzing the light curves of thousands of systems. In the near future, hundreds of thousands (possibly millions) of additional systems are expected to be discovered by Pan-STARRS, the Large Synoptic Survey Telescopes (LSST), and later by GAIA. Over the last decade, new classes of binary systems have also been found which contain Jupiter-size planets and binaries containing pulsating stars. Some examples of these important binaries are discussed. Also discussed are the increasing numbers (now eight) of eclipsing binary planet–star systems that have been found from high precision photometry. These systems are very important since the radii and masses of the hosted planets can be directly measured. Moreover, from the upcoming COROT and KEPLER missions hundreds of additional transiting planet-star systems are expected to be found. All in all, we hope in this paper to highlight some of the current developments and new directions in the “Brave New World” of binary star studies. 相似文献
10.
Martin D. Robards Michael L. SchoonChanda L. Meek Nathan L. Engle 《Global Environmental Change》2011,21(2):522-529
While a sustained flow of ecosystem services brings tangible benefits to humans, some ecosystem states and suites of services may be more desired by some people than others. Allocating or using the flow of services is loaded with asymmetries, complex power dynamics and political struggles between groups of people. We argue that the issues associated with such allocation and use questions are poorly integrated into the literatures of resilience, sustainability, and vulnerability. To illustrate this, we focus on three socially constructed factors that inhibit a fuller understanding about how to sustain the flow of ecosystem services: (1) rigidity/poverty traps; (2) power asymmetries; and (3) scientization of policy/politicization of science. These factors limit our ability to assess the sustainable flows of ecosystem services, and in particular to better understand the trade-offs and limits to aggregate human activity. We demonstrate that an improved understanding of the allocation trade-offs and limits to the flows of ecosystem services could result from more applied research that integrates the developing fields of deliberative democracy, pragmatic environmental philosophy, and legitimacy and rule compliance. Without the understanding that such integration would bring, researchers and policy makers risk underestimating the limits on flows of ecosystem services and how to accomplish their provision toward the greater collective - rather than individual - good. 相似文献