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881.
The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones. 相似文献
882.
We predict the decadal change in position of three American Samoa mangroves from analysis of a time series of remotely sensed
imagery, a geographic information system, tide gauge data, and projections for change in sea-level relative to the mangrove
surface. Accurate predictions of changes to coastal ecosystem boundaries, including in response to projected relative sea-level
rise, enable advanced planning to minimize and offset anticipated losses and minimize social disruption and cost of reducing
threats to coastal development and human safety. The observed mean landward migration of three mangroves' seaward margins
over four decades was 25, 64, and 72mma−1, 12 to 37 times the observed relative sea-level rise rate. Two of the sites had clear trends in reductions in mangrove area,
where there was a highly significant correlation between the change in position of the seaward mangrove margin and change
in relative sea-level. Here it can be inferred that the force of sea-level rise relative to the mangrove surface is causing
landward migration. Shoreline movement was variable at a third site and not significantly correlated with changing sea-level,
where it is likely that forces other than change in relative sea-level are predominant. Currently, 16.5%, 23.4%, and 68.0%
of the three mangroves' landward margins are obstructed by coastal development from natural landward migration. The three
mangroves could experience as high as a 50.0% reduction in area by the year 2100. A 12% reduction in mangrove area by the
year 2100 is possible in the Pacific islands region. 相似文献
883.
Sage M Coeurdassier M Defaut R Lucot E Barbier B Rieffel D Berny P Giraudoux P 《Environmental pollution (Barking, Essex : 1987)》2007,148(1):372-379
We aimed to evaluate whether environmental factors affect the persistence of bromadiolone in baits in field treatment. Baits were distributed in three soils according to two types of distribution: (1) artificial galleries conform to agricultural practices; (2) storage cavities to mimic bait storage by voles. Persistence was evaluated for 30 days in galleries and 80 days in storage cavities in autumn and spring. The decrease of bromadiolone concentrations was described by a first-order kinetic model. In galleries, the half-lives ranged from 3.0 to 5.1 days in autumn and from 5.4 to 6.2 days in spring. The half-lives were similar between soils and seasons but the pattern of persistence differed lightly for two soils between seasons. Half-lives in storage cavities, 42.7 and 24.6 days in autumn and spring respectively, were longer than in galleries. To conclude, both soil characteristics and climatic conditions weakly influence persistence, while bait storage lengthens it dramatically. 相似文献
884.
Lopez-Zamora I Bliss C Jokela EJ Comerford NB Grunwald S Barnard E Vasquez GM 《Environmental pollution (Barking, Essex : 1987)》2007,147(1):101-111
Pitch canker disease (Fusarium circinatum Nirenberg & O'Donnell) causes serious shoot dieback, reduced growth and mortality in pines found in the southern and western USA, and has been linked to nutrient imbalances. Poultry houses with forced-air ventilation systems produce nitrogen (N) emissions. This study analyzed spatial correlations between pitch canker disease and foliar, forest floor, soil, and throughfall N in a slash pine (Pinus elliottii var. elliottii Engelm.) plantation adjacent to a poultry operation in north Florida, USA. Tissue and throughfall N concentrations were highest near the poultry houses and remained elevated for 400 m. Disease incidence ranged from 57-71% near the poultry houses and was spatially correlated with N levels. Similarly, stem mortality ranged from 41-53% in the most heavily impacted area, and declined to 0-9% at distances greater than 400 m. These results suggest that nutritional processes exacerbate changes in disease susceptibility and expression in slash pine. 相似文献
885.
Humans sometimes forage or distribute the products of foraging in ways that do not maximize individual energetic return rates. As an alternative to hypotheses that rely on reciprocal altruism to counter the costs of inefficiency, we suggest that the cost itself could be recouped through signal benefit. Costly signaling theory predicts that signals can provide fitness benefits when costs are honestly linked to signaler quality, and this information is broadcast to potential mates and competitors. Here, we test some predictions of costly signaling theory against empirical data on human food acquisition and sharing patterns. We show that at least two types of marine foraging, turtle hunting and spearfishing, as practiced among the Meriam (a Melanesian people of Torres Strait, Australia) meet key criteria for costly signaling: signal traits are (1) differentially costly or beneficial in ways that are (2) honestly linked to signaler quality, and (3) designed to effectively broadcast the signal. We conclude that relatively inefficient hunting or sharing choices may be maintained in a population if they serve as costly and reliable signals designed to reveal the signaler's qualities to observers. 相似文献
886.
The choice of spatial and temporal scale used in environmental assessments may influence the observed results. One method
of assessing the impact of stream habitat alterations involves the comparison of response variables among treatment categories
(i.e., impacted and unimpacted sites). The influence of spatial resolution on patterns of response variables among treatment
categories in assessments of stream channelization and other types of habitat alterations has not been evaluated. We examined
how patterns of 10 community response variables among channel types and our interpretations of channelization impacts on fish
and macroinvertebrate communities differed among three spatial resolutions in a warmwater stream in Mississippi and Alabama.
Four fish and three macroinvertebrate community response variables exhibited different patterns among channel types at different
spatial resolutions. Our interpretations of the impacts of channelization on fish and macroinvertebrate communities differed
among spatial resolutions. Channelization had a negative influence on fish communities either with or without evidence of
potential community recovery in one channel type. Channelization impacts on macroinvertebrate communities ranged from a negative
influence to no effect. Our results suggest that spatial resolution can influence the observed results and interpretations
derived from assessments of stream habitat alterations. 相似文献
887.
M. Jason Todd Parker J. Wigington Jr. Eric A. Sproles 《Journal of the American Water Resources Association》2017,53(5):1008-1031
Hydrologic landscapes (HLs) have proven to be a useful tool for broad scale assessment and classification of landscapes across the United States as they help organize larger geographical areas into areas of similar hydrologic characteristics. We developed a HL classification for the Bristol Bay watershed of southwest Alaska that incorporates indices of annual climate and seasonality, terrain, geology, and the influences of large lakes and glaciers. A HL classification is particularly useful in this large watershed because of its hydrologic and landscape variability, important salmon fishery, variety of environmental and potential anthropogenic stressors, and lack of widespread hydrologic data. Following creation of Bristol Bay basin‐wide HL classes, we compared the HL distributions within watersheds grouped by two calculated runoff parameters derived from available long‐term streamflow records and found HL distributions within these groups provided predictive insight on hydrologic behavior. Using these developed runoff groups, we estimated expected hydrologic behavior in watersheds across the larger Bristol Bay watershed that lacked gauged streamflow records. The HL approach provides a scientific basis for estimating the first‐order hydrologic behavior of watersheds and landscapes that lack detailed hydrologic information. 相似文献
888.
Distribution of Selected Soil and Water Conservation Practices in the U.S. as Identified with Google Earth 下载免费PDF全文
Michael White Leighton Haglund Marcus Gloe Katrin Bieger Brandon Namphong Marilyn Gambone Eric Hardy Jungang Gao Haw Yen Jeff Arnold 《Journal of the American Water Resources Association》2017,53(5):1229-1240
The proper representation of conservation practices on agricultural lands is an important factor in large‐scale assessments of water quality in the United States. Unfortunately, there are few publicly available data sources at the local level and even fewer at the national scale. In this research, randomly selected points within agricultural lands were examined for selected conservation practices using Google Earth aerial imagery by a team of interpreters. In total, 13,530 points had field boundaries digitized, and were subsequently examined and classified. The presence of terraces, grassed waterways, contour farming, center pivot irrigation, strip cropping, ponds, riparian vegetation, filter strips, and land cover were noted. Subjectivity among interpreters was evaluated using duplicate samples and was found to be similar to image misclassification rates in other research. Conservation practice adoption rates for selected major river basins compared favorably with data collected by the Conservation Effects Assessment Project. The frequency of occurrence of each conservation practice was summarized and presented by ecoregion. To facilitate future research, point level data and software source code developed in this research are available via the web at http://nlet.brc.tamus.edu/Conservation . Aerial imagery was found to be a powerful, inexpensive, and easily accessible tool to assess large‐scale conservation practice implementation for certain conservation practices. 相似文献
889.
George F. Antonious Eric T. Turley Mutari Abubakari John C. Snyder 《Journal of environmental science and health. Part. B》2017,52(4):251-255
The persistence and fate of chlorpyrifos and its two metabolites, chlorpyrifos-oxon and the 3, 5, 6-trichloro-2-pyridinol (TCP) break-down product were investigated on kale and collard leaves under field conditions. A simultaneous extraction and quantification procedure was developed for chrorpyrifos and its two main metabolites. Residues of chlorpyrifos, chlorpyrifos oxon, and TCP were determined using a gas chromatograph (GC) equipped with an electron capture detector (GC/ECD). Chlorpyrifos metabolites were detectable up to 23 days following application. Residues were confirmed using a GC equipped with a mass selective detector (GC/MSD) in total ion mode. Initial residues of chlorpyrifos were greater on collard (14.5 µg g?1) than kale (8.2 µg g?1) corresponding to half-lives (T1/2) values of 7.4 and 2.2 days, respectively. TCP, the hydrolysis product, was more persistent on collards with an estimated T1/2 of 6.5 days compared to kale (T1/2 of 1.9 days). 相似文献
890.
Bour Agathe Mouchet Florence Cadarsi Stéphanie Silvestre Jérôme Baqué David Gauthier Laury Pinelli Eric 《Environmental science and pollution research international》2017,24(20):17081-17089
Environmental Science and Pollution Research - We studied the fate and toxicity of two types of CeO2 NPs (bare or citrate-coated) in environmentally relevant conditions, using large indoor... 相似文献