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201.
Ann Salomon Bleed 《Journal of the American Water Resources Association》1987,23(6):1173-1178
ABSTRACT: Today most rivers are not freely flowing but are highly regulated to meet both human and wildlife needs. Several models allow the determination of instream flows that are needed to meet wildlife demands. However, these models are based on assumptions that limit their applicability to certain types of rivers. While these limitations do not preclude the use of the models on other types of rivers, like the Platte River in Nebraska, their limitations should be considered and accommodated by those making instream flow planning and management decisions. Other factors affecting channel morphology and its associated wildlife habitat, such as threshold values and vegetation are not adequately considered by current concepts. If rivers are to be managed to provide wildlife habitat, these factors will have to be addressed. 相似文献
202.
Characterization of Infiltration Rates from Landfills: Supporting Groundwater Modeling Efforts 总被引:4,自引:0,他引:4
Moo-Young H Johnson B Johnson A Carson D Lew C Liu S Hancocks K 《Environmental monitoring and assessment》2004,96(1-3):283-311
The purpose of this paper is to review the literature to characterize infiltration rates from landfill liners to support groundwater modeling efforts. The focus of this investigation was on collecting studies that describe the performance of liners 'as installed' or 'as operated'. This document reviews the state of the science and practice on the infiltration rate through compacted clay liner (CCL) for 149 sites and geosynthetic clay liner (GCL) for 1 site. In addition, it reviews the leakage rate through geomembrane (GM) liners and composite liners for 259 sites. For compacted clay liners (CCL), there was limited information on infiltration rates (i.e., only 9 sites reported infiltration rates.), thus, it was difficult to develop a national distribution. The field hydraulic conductivities for natural clay liners range from 1 x 10(-9) cm s(-1) to 1 x 10(-4) cm s(-1), with an average of 6.5 x 10(-8) cm s(-1). There was limited information on geosynthetic clay liner. For composite lined and geomembrane systems, the leak detection system flow rates were utilized. The average monthly flow rate for composite liners ranged from 0-32 lphd for geomembrane and GCL systems to 0 to 1410 lphd for geomembrane and CCL systems. The increased infiltration for the geomembrane and CCL system may be attributed to consolidation water from the clay. 相似文献
203.
Ann Verdoodt Stephen M. Mureithi Liming Ye Eric Van Ranst 《Agriculture, ecosystems & environment》2009,129(1-3):332-339
The establishment of enclosures has become an important measure to combat land degradation in many of the world's semi-arid rangelands. In view of the increased pressure exerted by this land reclamation strategy on the neighbouring agricultural lands, knowledge of the time required for restoring vegetation cover and soil health, and of the potential positive impact of an adapted management strategy, is highly required. This paper assesses the vegetation and soil rehabilitation in a 23-year chronosequence of two different enclosure management types. In the severely degraded, semi-arid Njemps Flats plain of the Lake Baringo Basin in Kenya communal enclosures characterised by high quality inputs and strict control, and private enclosures managed by individual farmers, were installed since the 1980s. Six communal enclosures (3–17 years since establishment) and six private enclosures (13–23 years since establishment) were selected. Vegetation cover was estimated along three 50 m transects set within each enclosure and in the adjacent open grazing area using the point-to-line transect method. Five 0.5 m2 quadrats systematically placed alongside each transect were sampled for herbaceous standing biomass and topsoil physical, chemical and biological analyses. Grass cover and herbaceous biomass production proved to be the most responsive biotic parameters under both management types, whereas the recovery of the forbs was unsuccessful. Under communal management, the biomass production fully recovered up to its optimal level as recorded in the neighbouring nature reserves. Within private enclosures however, the adopted management strategies seriously restricted biomass production to a significantly lower level. Soil quality generally recovered more slowly with time. Significant improvements compared to the open rangeland were recorded in topsoil bulk density, organic C and total N stocks, and microbial biomass C and N stocks of the communal enclosures. Unlike the communal enclosures, only topsoil bulk density and the microbial biomass C stock showed a significant difference in the private enclosures. With respect to C and total N stocks, and the microbial biomass N a non-significant improving trend was recorded. The level of chemical and biological soil quality obtained under both management types is still low and draws the attention to the importance of careful monitoring of grazing and grass cutting activities under both enclosure management strategies. The chronosequences further highlight the potential of some well-managed private enclosures, whereas intrinsic soil properties such as high alkalinity, as well as changes in management, limit the rehabilitation of some other private as well as communal enclosures. 相似文献
204.
Ann M. Bailey Timothy L. McMurry Gerald S. Poplin Robert S. Salzar Jeff R. Crandall 《Traffic injury prevention》2015,16(7):S96-S102
Objectives: Understanding how lower extremity injuries from automotive intrusion and underbody blast (UBB) differ is of key importance when determining whether automotive injury criteria can be applied to blast rate scenarios. This article provides a review of existing injury risk analyses and outlines an approach to improve injury prediction for an expanded range of loading rates. This analysis will address issues with existing injury risk functions including inaccuracies due to inertial and potential viscous resistance at higher loading rates.Methods: This survival analysis attempts to minimize these errors by considering injury location statistics and a predictor variable selection process dependent upon failure mechanisms of bone. Distribution of foot/ankle/leg injuries induced by axial impact loading at rates characteristic of UBB as well as automotive intrusion was studied and calcaneus injuries were found to be the most common injury; thus, footplate force was chosen as the main predictor variable because of its proximity to injury location to prevent inaccuracies associated with inertial differences due to loading rate. A survival analysis was then performed with age, sex, dorsiflexion angle, and mass as covariates. This statistical analysis uses data from previous axial postmortem human surrogate (PMHS) component leg tests to provide perspectives on how proximal boundary conditions and loading rate affect injury probability in the foot/ankle/leg (n = 82).Results: Tibia force-at-fracture proved to be up to 20% inaccurate in previous analyses because of viscous resistance and inertial effects within the data set used, suggesting that previous injury criteria are accurate only for specific rates of loading and boundary conditions. The statistical model presented in this article predicts 50% probability of injury for a plantar force of 10.2 kN for a 50th percentile male with a neutral ankle position. Force rate was found to be an insignificant covariate because of the limited range of loading rate differences within the data set; however, compensation for inertial effects caused by measuring the force-at-fracture in a location closer to expected injury location improved the model's predictive capabilities for the entire data set.Conclusions: This study provides better injury prediction capabilities for both automotive and blast rates because of reduced sensitivity to inertial effects and tibia–fibula load sharing. Further, a framework is provided for future injury criteria generation for high rate loading scenarios. This analysis also suggests key improvements to be made to existing anthropomorphic test device (ATD) lower extremities to provide accurate injury prediction for high rate applications such as UBB. 相似文献
205.
Ann Hedlund Author Vitae Mattias Åteg Author VitaeAuthor Vitae Gunnar Rosén Author Vitae 《Journal of Safety Research》2010,41(2):145-151
Problem
Workers' motivation to actively take part in improvements to the work environment is assumed to be important for the efficiency of investments for that purpose. That gives rise to the need for a tool to measure this motivation.Method
A questionnaire to measure motivation for improvements to the work environment has been designed. Internal consistency and test-retest reliability of the domains of the questionnaire have been measured, and the factorial structure has been explored, from the answers of 113 employees.Results
The internal consistency is high (0.94), as well as the correlation for the total score (0.84). Three factors are identified accounting for 61.6% of the total variance.Discussion
The questionnaire can be a useful tool in improving intervention methods.Impact on Industry
The expectation is that the tool can be useful, particularly with the aim of improving efficiency of companies' investments for work environment improvements. 相似文献206.
Mary Ann Thomas 《Journal of the American Water Resources Association》2000,36(5):1023-1038
ABSTRACT: Two water‐quality studies were done on the outskirts of the Detroit metropolitan area to determine how recent residential development has affected ground‐water quality. Pairs of monitor and domestic wells were sampled in areas where residential land use overlies glacial outwash deposits. Young, shallow waters had significantly higher median concentrations of nitrate, chloride, and dissolved solids than older, deeper waters. Analysis of chloride/bromide ratios indicates that elevated salinities are due to human activities rather than natural factors, such as upward migration of brine. Trace concentrations of volatile organic compounds were detected in samples from 97 percent of the monitor wells. Pesticides were detected infrequently even though they are routinely applied to lawns and roadways in the study area. The greatest influence on ground‐water quality appears to be from septic‐system effluent (domestic sewage, household solvents, water‐softener backwash) and infiltration of storm‐water runoff from paved surfaces (road salt, fuel residue). No health‐related drinking‐water standards were exceeded in samples from domestic wells. However, the effects of human activities are apparent in 76 percent of young waters, and at depths far below 25 feet, which is the current minimum well‐depth requirement. 相似文献
207.
Carin Jantzen Christian Wild Mohammed El-Zibdah Hilly Ann Roa-Quiaoit Christoph Haacke Claudio Richter 《Marine Biology》2008,155(2):211-221
Two species of giant clams, Tridacna maxima and T. squamosa, coexist in the Red Sea, but exhibit distinctly different depth distributions: T. maxima mostly occurs in shallow waters (reef flat and edge), while T. squamosa may occur down to the lower fore-reef slope. Giant clams have been described as mixotrophic, capable of both filter-feeding
and photosynthesis due to algal symbionts (zooxanthellae), therefore, observed depth preferences were investigated in relation
to possible differences in autotrophy vs. heterotrophy. This study was conducted from April to June 2004, at the reef near
the Marine Science Station, Aqaba, Gulf of Aqaba, Red Sea, and in May 2007, at a reef near Dahab, Sinai Peninsula, Egypt.
In situ measurements using a submersible pulse amplitude modulated fluorometer (Diving PAM), revealed no significant differences
in effective PSII quantum yield (ΔF/Fm′) and relative electron transport rates (ETR) between the two species; but rapid light curves (ETR vs. light, photosynthetically
active irradiance, PAR) showed significant differences in maximum photosynthetic rates (ETRmax), with 20% higher values in T. maxima. Chamber incubations displayed higher net and gross oxygen production by T. maxima (88.0 and 120.3 μmol O2 cm−2 mantle area day−1) than T. squamosa (56.7 and 84.8 μmol O2 cm−2 mantle area day−1); even under shading conditions (simulated depth of 20 m) T. maxima still achieved 93% of the surface gross O2 production, whereas T. squamosa reached only 44%. A correlation was found between ETR and net photosynthesis measured as oxygen production (T. maxima: R
2 = 0.53; T. squamosa: R
2 = 0.61). Calculated compensation depth (CD) (gross photosynthesis equals respiration) in T. maxima (16 m) matches the maximum depth of occurrence in this study (17 m). By contrast, the CD of T. squamosa (9 m) was much shallower than the maximum vertical range (42 m). Findings suggest T. maxima is a strict functional photoautotroph limited by light, whereas T. squamosa is a mixotroph whose photoautotrophic range is extended by heterotrophy.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
208.
Yamagishi Kafferine Ocampo Lanndon Abellana Dharyll Prince Tanaid Reciel Ann Tiu Ann Myril Medalla Maria Esther Selerio Egberto Go Chrisalyn Olorvida Rey Cesar Maupo Amalia Maskariño Dearielyn Tantoo Emilyn 《Environment, Development and Sustainability》2021,23(10):14998-15030
Environment, Development and Sustainability - The current literature has espoused the role of social media platforms in promoting tourism destinations. Despite such advances, limited works are... 相似文献
209.
Hannelore Mees Ann Crabbé Peter P.J. Driessen 《Journal of Environmental Policy & Planning》2017,19(6):827-842
Across Europe, there is an increasing trend towards citizen involvement in the implementation of flood risk governance. Policy-makers increasingly advocate co-produced flood risk governance (FRG), whereby citizens are actively engaged in the implementation of flood risk policy, for example, by taking property-level protection measures. In doing so, they aim to make FRG more resilient, efficient and legitimate [Mees, H., Crabbé, A., Alexander, M., Kaufmann, M., Bruzzone, L., Levy, L., & Lewandowski, J. (2016a). Coproducing flood risk management through citizen involvement: Insights from cross-country comparison in Europe. Ecology and Society, 21(3), 7. http://dx.doi.org/10.5751/ES-08500-210307]. Co-production, however, also raises important questions concerning these aims. In this paper, the opportunities and limitations of and barriers to citizen co-production in FRG in terms of resilience, efficiency and legitimacy are investigated by an extensive review of literature on citizen co-production in other public services and on individual and community-based climate change adaptation and FRG. Based on this, a tentative framework is developed on the required conditions to enable co-produced FRG, which benefits both the resilience, efficiency and legitimacy of FRG. 相似文献
210.
Determination of steroidal estrogens in flushed dairy manure wastewater by gas chromatography-mass spectrometry 总被引:1,自引:0,他引:1
Hanselman TA Graetz DA Wilkie AC Szabo NJ Diaz CS 《Journal of environmental quality》2006,35(3):695-700
There is a critical need to accurately measure the concentrations of natural steroidal estrogens in flushed dairy manure wastewater (FDMW) to assess any potential risk of waterway contamination resulting from land application. Estrogens are a concern because low concentrations (10-100 ng L-1) in water can adversely affect aquatic vertebrate species such as fish, turtles, and frogs by disrupting the normal function of their endocrine systems. The objective of this study was to develop a sample preparation method that permits the quantification of four natural steroidal estrogens (17alpha-estradiol, 17beta-estradiol, estrone, and estriol) in FDMW by gas chromatography-mass spectrometry (GC-MS). Solid-phase extraction with graphitized carbon black was used for the bulk extraction of estrogens from FDMW and additional sample purification was accomplished with C-18. The sample preparation method allowed estrogens to be detected accurately by GC-MS in FDMW. Spiked recovery experiments indicated that the method is satisfactory for measuring the estrogens of interest in FDMW with average recovery of >90%. As expected in FDMW, characterization of the estrogen profile revealed a large abundance of 17alpha-estradiol relative to 17beta-estradiol and estrone. Estriol was not detected in FDMW. The methodology developed in this research helps provide an analytical foundation for the quantification of steroidal estrogens in FDMW by GC-MS. 相似文献