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Simulation of historical temperatures using a multi‐site,multivariate block resampling algorithm with perturbation 
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下载免费PDF全文 Stochastic weather generators have evolved as tools for creating long time series of synthetic meteorological data at a site for risk assessments in hydrologic and agricultural applications. Recently, their use has been extended as downscaling tools for climate change impact assessments. Non‐parametric weather generators, which typically use a K‐nearest neighbour (K‐NN) resampling approach, require no statistical assumptions about probability distributions of variables and can be easily applied for multi‐site use. Two characteristics of traditional K‐NN models result from resampling daily values: (1) temporal correlation structure of daily temperatures may be lost, and (2) no values less than or exceeding historical observations can be simulated. Temporal correlation in simulated temperature data is important for hydrologic applications. Temperature is a major driver of many processes within the hydrologic cycle (for example, evaporation, snow melt, etc.) that may affect flood levels. As such, a new methodology for simulation of climate data using the K‐NN approach is presented (named KnnCAD Version 4). A block resampling scheme is introduced along with perturbation of the reshuffled daily temperature data to create 675 years of synthetic historical daily temperatures for the Upper Thames River basin in Ontario, Canada. The updated KnnCAD model is shown to adequately reproduce observed monthly temperature characteristics as well as temporal and spatial correlations while simulating reasonable values which can exceed the range of observations. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Sophia E. Fox Mirta Teichberg Ivan Valiela Leanna Heffner 《Estuaries and Coasts》2012,35(5):1193-1204
Understanding whether nutrient availability and grazing by consumers can control macroalgal growth is important to mitigate blooms. To assess the effect of long-term nitrogen loading on macroalgae, we ran a field experiment in which we measured growth of green and red macroalgae in estuaries where loads and eutrophication status differed. The relative abundances of consumers differed among estuaries with more grazers in non-eutrophied estuaries, an important interaction of bottom-up and top-down controls. In the estuary with the lowest nitrogen load, grazers controlled green macroalgal growth, but in higher nitrogen-loaded estuaries, where grazing was lower, growth of green macroalgae overwhelmed potential grazer control. The red macroalga was not controlled by grazers, even in the estuary where grazing pressure was highest. In the low-loaded estuary, invertebrate predators exerted top-down control over grazers, but predation effects did not cascade to macroalgae. Bottom-up mechanisms dominated control of macroalgae through an interaction of direct stimulation of growth and indirect alteration of consumer abundances, and thus, long-term nutrient regimes are likely determining potential for bloom formation in Waquoit Bay. 相似文献
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Ben K. Odhiambo Virginia Brown Gayle Armentrout Leanna C. Giancarlo Chelsea Wegner 《Environmental Earth Sciences》2013,69(6):2103-2117
Damming of the North Anna River in 1972 created Lake Anna, a cooling water source for the Dominion nuclear power plant as well as a popular recreation site in Spotsylvania and Orange counties, Virginia, USA. Previously dated (210-Pb) sediment cores from seven locations within the lake and three locations in the adjoining Waste Heat Treatment Facilities (WHTF) were analyzed for trace metals (Al, Ba, Zn, Cd, Cu, Fe, Mn and Pb) and polychlorinated biphenyls (PCBs) to examine the environmental evolution of the reservoir system. The reservoir has a history of mining activities in its watershed and unusually elevated concentrations of PCBs were found in fish tissues from previous studies. Therefore, dated sediment cores provided the framework for both the temporal and spatial analysis of possible sources and flux histories for both trace metals and PCBs. The trace metals results suggest that, though the upper reaches are relatively less impacted, the old mine tailings from the now ceased mining activities in the watershed of Contrary Creek tributary continue to dominate the sediment chemistry of the lower portion of the lake basin, signified by sediment enrichment of Pb, Cd, Cu, and Zn. Lagoon-2 of the WHTF also seems to be receiving unusually high loadings of Cd (12.5 ± 1.07 μg/g) that is probably associated with waste materials from the nuclear power plant that maintains the lagoons. PCB sediment concentrations were relatively low in the lower sections of the basins with values typically being <3.5 ng/g. The upper reaches of the basin had several PCB hotspots, with the surface sediments of Terry’s Run tributary having values as high as 53.13 ng/g. The spatial distribution of PCBs seems to suggest the upper reaches of the basin as the probable source, with the unusually high concentrations near bridges suggesting a possible link between the PCBs and old bridge fill materials. The oldest lacustrine sediments also had relatively high trace metals and PCB values signifying a probable role of soil disruption and sediment reconcentration during reservoir construction. 相似文献
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The Groundwater Monitoring Program at the Savannah River Plant currently consists of more than 700 wells at more than 70 sites, and growth is projected. The organization and operation of the program has been designed to support an active drilling program, the acquisition of a large amount of repetitive data, the generation of numerous reports, associated QA/QC controls, and provisions for additional growth. The design is centered around two key features—modular components and computer usage.
The modular component concept is an organizational tool that gives one group responsibility for a specific portion of the program. This responsibility includes the operation of its segment and the coordination of operations with the other groups in the program.
Computers, the associated software programs, and a simple set of rules (the sampling guide) enables the program to accommodate large amounts of repetitive data in a timely, uniform manner. Feedback loops are included to ensure that new data are incorporated into future program decisions (new sample schedules and well locations). The highly automated system determines new sample schedules, collates/reviews incoming data, and generates various reports. Six reports are issued on a regular basis, from quarterly to annually, to ensure that the program is adequately documented.
The program has been in successful operation for more than a year and has accommodated the expected growth. 相似文献
The modular component concept is an organizational tool that gives one group responsibility for a specific portion of the program. This responsibility includes the operation of its segment and the coordination of operations with the other groups in the program.
Computers, the associated software programs, and a simple set of rules (the sampling guide) enables the program to accommodate large amounts of repetitive data in a timely, uniform manner. Feedback loops are included to ensure that new data are incorporated into future program decisions (new sample schedules and well locations). The highly automated system determines new sample schedules, collates/reviews incoming data, and generates various reports. Six reports are issued on a regular basis, from quarterly to annually, to ensure that the program is adequately documented.
The program has been in successful operation for more than a year and has accommodated the expected growth. 相似文献
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Leanna Woods Pan Robert L. Siegrist Michelle Crimi 《Ground Water Monitoring & Remediation》2012,32(2):96-105
In situ remediation technologies have the potential to alter subsurface properties such as natural organic matter (NOM) content or character, which could affect the organic carbon‐water partitioning behavior of chlorinated organic solvents, including dense nonaqueous phase liquids (DNAPLs). Laboratory experiments were completed to determine the nature and extent of changes in the partitioning behavior of trichloroethene (TCE) caused by in situ chemical oxidation or in situ surfactant flushing. Sandy porous media were obtained from the subsurface at a site in Orlando, Florida. Experiments were run using soil slurries in zero‐headspace reactors (ZHRs) following a factorial design to study the effects of porous media properties (sand vs. loamy sand with different total organic carbon [TOC] contents), TCE concentration (DNAPL presence or absence), and remediation agent type (potassium permanganate vs. activated sodium persulfate, Dowfax 8390 vs. Tween 80). Results revealed that the fraction of organic carbon (foc) of porous media after treatment by oxidants or surfactants was higher or lower relative to that in the untreated media controls. Isotherm experiments were run using the treated and control media to measure the distribution coefficient (Kd) of TCE. Organic carbon‐water partitioning coefficient values (Koc) calculated from the experimental data revealed that Koc values for TCE in the porous media were altered via treatment using oxidants and surfactants. This alteration can affect the validity of estimates of contaminant mass remaining after remediation. Thus, potential changes in partitioning behavior should be considered to help avoid decision errors when judging the effectiveness of an in situ remediation technology. 相似文献
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Florence V. Dunkel Leanna M. Hansen Sarah J. Halvorson Arthur Bangert 《GeoJournal》2017,82(4):841-865
We assess women’s perceptions of health risks in relation to quality of life concerns, with attention to variables viewed as central to maintaining or improving health and well-being. In this paper, we specifically underscore how a life-threatening disease—malaria—is experienced and bio-cyclically understood and managed in relation to seasonal hunger, food insecurities, and livelihood vulnerabilities. The study, conducted June–July 2013, draws on field data and interviews with 60 women farmers of the Luhya community along the Yala River in Kakamega County, Western Province, Kenya. Major findings suggest the following: (1) women’s perceived desired quality of life is shaped by priorities for children’s education, nutrition, food security, and economic security in their rural communities; (2) malaria emerged as a challenging household health problem that curtails livelihood opportunities for most study participants; and (3) local understandings of malaria transmission, particularly how and when female mosquitoes become infected with malaria-causing protozoans, was low, but malaria symptoms were relatively well-understood. The interest and motivation to institute new malaria risk reduction practices at the community level are explored, including attention to building upon the Luhya tradition of oral storytelling in order to promote actions to eliminate malaria. This analysis of local narratives of health risks illustrates these points and demonstrates how women’s constructions of health risks and well-being provide a basis for developing interventions targeting income generation and microloan opportunities that could support Kenyan women in their intersecting approaches to malaria, securing nutritious diets, and enhancing the local health environment. 相似文献
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Autumn Oczkowski Courtney Schmidt Emily Santos Kenneth Miller Alana Hanson Donald Cobb Jason Krumholz Adam Pimenta Leanna Heffner Sandra Robinson Joaquín Chaves Rick McKinney 《Estuaries and Coasts》2018,41(8):2260-2276
Over the past decade, nitrogen (N) loads to Narragansett Bay have decreased by more than 50%. These reductions were, in large part, the direct result of multiple wastewater treatment facility upgrades to tertiary treatment, a process which employs N removal. Here, we document ecosystem response to the N reductions and assess how the distribution of sewage N in Narragansett Bay has changed from before, during, and shortly after the upgrades. While others have observed clear responses when data were considered annually, our seasonal and regional comparisons of pre- and post-tertiary treatment dissolved inorganic nitrogen (DIN) concentrations and Secchi depth data, from bay-wide surveys conducted periodically from the early 1970s through 2016, resulted in only a few subtle differences. Thus, we sought to use stable isotope data to assess how sewage N is incorporated into the ecology of the Bay and how its distribution may have changed after the upgrades. The nitrogen (δ15N) and carbon (δ13C) stable isotope measurements of particulate matter served as a proxy for phytoplankton, while macroalgae served as short-term integrators of water column bio-available N, and hard clams (Mercenaria mercenaria) as integrators of water column production. In contrast to other estuarine stable isotope studies that have observed an increased influence of isotopically lower marine N when sewage N is reduced, the opposite has occurred in Narragansett Bay. The tertiary treatment upgrades have increased the effluent δ15N values by at least 2‰. The plants and animals throughout Narragansett Bay have similarly increased by 1–2‰, on average. In contrast, the δ13C values measured in particulate matter and hard clams have declined by about the same amount. The δ15N results indicated that, even after the N reductions, sewage N still plays an important role in supporting primary and secondary production throughout the bay. However, the δ13C suggests that overall net production in Narragansett Bay has decreased. In the 5 years after the major wastewater treatment facilities came on-line for nutrient removal, oligotrophication has begun but sewage remains the dominant source of N to Narragansett Bay. 相似文献
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