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At least 19 recordsLinked to original sources

Food security in a changing climate

By 2080 the effects of climate change—on heat waves, floods, sea level rise, and drought—could push an additional 600 million people into malnutrition and increase the number of people facing water scarcity by 1.8 billion. The precise impacts will, however, strongly depend on socioeconomic conditions such as local markets and food import dependence. In the near term, two factors are also changing the nature of food security: (1) rapid urbanization, with the proportion of the global population living in urban areas expanding from 13 percent in 1975 to greater than 50 percent at present, and (2) trade and domestic market liberalization since 1993, which has promoted removal of import controls, deregulation of prices, and the loss of preferential markets for many small economies. Over the last two years, the worst drought in decades has devastated eastern Africa. The resulting food-security crisis has affected roughly 13 million people and has reminded us that there is still a long way to go in addressing current climate-related risks. In the face of such profound changes and uncertainties, our approaches to food security must evolve. In this article, we describe four key elements that, in our view, will be essential to the success of efforts to address the linked challenges of food security and climate change.

Solutions Journal↗

Managing conflicts in the River of Grass

Chances are, you would not pack up and move to a new home without first researching the neighborhood, reviewing your finances, and maybe investigating schools nearby. Similarly, you would not buy the first car you find on a magazine cover without first reviewing the technical specifications, exploring your options, and perhaps taking a test drive. Even when making simple purchases online, you probably shop around, check out customer reviews, and scan seller feedback ratings. Rarely do we act on impulse alone when faced with decisions. Rather, we typically start with a vision of what we want before gathering the necessary information, weighing our options, prioritizing our values, and evaluating possible tradeoffs. In making choices that range from lighthearted to life-changing, we use this commonsense strategy every day of our lives. Environmental decision-making is no different. For decades, natural resource managers faced with complicated problems have made decisions by breaking them into smaller components that are easier to approach. And like our day-to day decisions, the process is ideally guided by a shared vision of the future. However, it can become complicated when multiple, seemingly disparate views on what the future should hold emerge. As Lewis Carroll once wrote, “If you don’t know where you are going, any road will get you there.” Divining a vision of the future for the Florida Everglades and making supporting decisions is a complex undertaking. But unlike Alice thrust through the looking glass, we have tools and techniques to help us make sense of it all. The application of tools to help decision-making can move us closer to the successful restoration of this imperiled landscape.

Florida↗

Tropical wetlands in the Anthropocene: The critical role of wet-dry cycles

In the face of climate change and increasing human water demands for agriculture, industry, and cities, the fate of wetland ecosystems in tropical wet-dry climates is threatened. To maximize biodiversity and ecological resilience, the value of the ecosystem services provided by tropical wetlands can be incorporated into regional land use and water management decisions. Environmental planners and resource managers can work to protect both the “dry” and “wet” phases of the wet-dry hydrologic cycles. These cycles have shaped and maintained these ecosystems in the past and they can be used to maximize biodiversity and resilience in the future.

Solutions Journal↗

Turning on the faucet to a healthy coast

Coastal re-engineering and freshwater extraction have reduced water flow into the estuaries of the world. Because of these activities, stressed coastal vegetation is especially vulnerable to die-off during droughts, contributing to a loss of human services related to storm protection, fisheries and water quality. The subsequent collapse of vegetation is often as related to the loss of flow as to the rise in salinity. The solution to the problem in regions with rapidly expanding human populations may be to apply strategically timed freshwater releases to estuaries. To be successful, the water requirements of both humans and natural environments need careful assessment. Flow management projects have been successful in reviving vegetation in a number of settings including The Everglades, Murray River, Mississippi River and Nueces River. These projects can be contentious, for example, if the projects have caused negative impacts to the oyster industry. Beyond the human services provided, flowing water has an intrinsic personal value for which many people are willing to pay.

Solutions Journal↗

An investigation of the critical liquid-vapor properties of dilute KCl solutions

The three parameters that define the critical point, temperature, pressure, and volume have been experimentally determined by means of filling studies in a platinum-lined system for five KCl solutions ranging from 0.006 to 0.568 m . The platinum-lined vessels were used to overcome the problems with corrosion experienced by earlier workers. The critical temperature ( t c ), pressure ( P c ), and volume ( V c ) were found to fit the equations t c = 374.14   +   16.602 m   +   41.740 m  ± 0.5 ∘ C P c = 220.9   +   135.164 m  +   41.173 m 2   ±   0.5 b a r s V c = 3.155   −   1.373 m   +   0.507 m  ±   0.008 c m 3 − g − 1 "> t c = 374.14 + 16.602 m −−√ + 41.740 m ± 0.5 ∘ C P c = 220.9 + 135.164 m + 41.173 m 2 ± 0.5 b a r s V c = 3.155 − 1.373 m −−√ + 0.507 m ± 0.008 c m 3 − g − 1 tc=374.14 + 16.602m + 41.740m ±0.5∘CPc=220.9 + 135.164m + 41.173m2 ± 0.5barsVc=3.155 − 1.373m + 0.507m ± 0.008cm3−g−1 from infinite dilution to 1.0 m .

Journal of Solution Chemistry↗

The solubility of the noble gases He, Ne, Ar, Kr, and Xe in water up to the critical point

The solubility of the noble gases Ar, He, Ne, Kr, and Xe in pure water was measured from 298 to 561??K. These data in turn were extrapolated to the critical point of water, thus providing a complete set of Henry's law constants from 274 to 647??K when combined with the existing literature data. Equations describing the behavior of the Henry's law constants over this temperature range are also given. The data do not confirm extrapolations of empirical correlations based on low-temperature solubility data. ?? 1978 Plenum Publishing Corporation.

Journal of Solution Chemistry↗

The Unified Lunar Control Network 2005

This report documents a new general unified lunar control network and lunar topographic model based on a combination of Clementine images and a previous network derived from Earth-based & Apollo photographs, and Mariner 10, & Galileo images. This photogrammetric network solution is the largest planetary control network ever completed. It includes the determination of the 3-D positions of 272,931 points on the lunar surface and the correction of the camera angles for 43,866 Clementine images, using 546,126 tie point measurements. The solution RMS is 20 μm (= 0.9 pixels) in the image plane, with the largest residual of 6.4 pixels. The explanation given here, along with the accompanying files, comprises the release of the network information and of global lunar digital elevation models (DEMs) derived from the network. A paper that will describe the solution and network in further detail will be submitted to a refereed journal, and will include additional background information, solution details, discussion of accuracy and precision, and explanatory figures.

Open-File Report↗

Finite volume model for two-dimensional shallow environmental flow

This paper presents the development of a two-dimensional, depth integrated, unsteady, free-surface model based on the shallow water equations. The development was motivated by the desire of balancing computational efficiency and accuracy by selective and conjunctive use of different numerical techniques. The base framework of the discrete model uses Godunov methods on unstructured triangular grids, but the solution technique emphasizes the use of a high-resolution Riemann solver where needed, switching to a simpler and computationally more efficient upwind finite volume technique in the smooth regions of the flow. Explicit time marching is accomplished with strong stability preserving Runge-Kutta methods, with additional acceleration techniques for steady-state computations. A simplified mass-preserving algorithm is used to deal with wet/dry fronts. Application of the model is made to several benchmark cases that show the interplay of the diverse solution techniques.

Journal of Hydraulic Engineering↗

Analysis of slump slip lines and deformation fabric in slumped Pleistocene lake beds

Slumped glacial delta sands and silts exhibit flexural slip folds and low-angle thrust faults where the beds remained coherent during slump deformation. Alternating cross-cutting relationships between f (sub l ) and f (sub r ) fold axial planes indicate that these fold groups are conjugate sets, related to the same slump movement. Analysis of slump fold axis orientations by the separation-angle method yields the fold slip plane and fold slip line. A deformation fabric reference diagram, deduced from fold and thrust fault data, shows a vertical deformation plane that is defined by the pole to the f (sub l ) and f (sub r ) fold slip planes, pole to rotated bedding, pole to thrust faults, and the fold slip lines. Central tendency estimators, Theta , Theta , and P 50 , of distributions of fold azimuths show close agreement, as do dispersion indicators sigma , derived from L values, and (P 84 -P 16 )/2. Fold axis orientations in the slumped mass are normally distributed, but the perpendiculars to deduced slip lines have consistently higher azimuth values than other central tendency values. These results may indicate that the sampling plain biased the populations. In this case, the vector mean is not perpendicular to the deduced slip line. Silt intraclast breccias, containing slump overfolds, appear to have been deposited as noncoherent grain flows in the slump depression subsequent to slump deformation. The distribution of overfold axis orientations is not significantly different from random distributions. Separation-angle analysis of the same lower breccia data yields a valid slip line solution.

New Hampshire↗

Perched silica minerals on mordenite fiber

Ellipsoidal quartz grains and spherulitic chalcedony are perched on mordenite fibers in geodes from Chihuahua, Mexico. Examination of samples of fibrous mordenite from six additional localities indicated that most mordenites have perched quartz crystals. A linear relationship exists between the Si:Al ratios and the refractive indices of the mordenites. The pH of the mineralizing solutions appears to be the primary factor controlling the presence of perched silica minerals (the lower the pH, the higher the Si:Al ratios and the lower the probability of precipitating quartz). Other factors that may affect the presence of lurched silica minerals are (1) the compactness of the mordenite fibers, (2) the morphology of the fibers, and (3) the concentration of Al, Ca, Na, and K in the mineralizing solutions.

Journal of Research of the U.S. Geological Survey↗

Radiochemical determination of very low concentrations of nickel in rocks and minerals

A radiochemical procedure has been developed for the determination of very low concentrations of nickel in rocks and minerals. Sensitivity is 0.01 μ g Ni. Accuracy and precision is estimated to be ±5 percent to levels as low as 0.1 μ g Ni a marked improvement over other analytical techniques. Samples are irradiated, combined with nickel carrier, and treated by a series of chemical procedures: (1) collection of nickel in a lead bead using a fire-assay technique, (2) refusion of the lead bead and precipitation of basic element hydroxides, (3) anion-exchange chromatography, and (4) precipitation of nickel dimethylglyoxime. The nickel precipitate is weighed to determine chemical yield and counted for β activity of Ni 65 along with a precipitate from irradiated nickel standard solution.

Journal of Research of the U.S. Geological Survey↗

Application of a hollow-fiber, tangential-flow device for sampling suspended bacteria and particles from natural waters

The design and application of a hollow-fiber tangential-flow filtration device has been used to concentrate bacteria and suspended particles from large volume surface water and groundwater samples (i.e., hundreds of liters). Filtrate tlux rates (4–8 L min −1 ) are equal to or faster than those of other devices that are based on continuous flow centrifugation and plate and frame filtration. Particle recovery efficiencies for inorganic particles (approximately 90%) were similar to other dewatering devices, but microbial cell recoveries (30–90%) were greatly improved by this technique relative to other currently available methods. Although requirements for operation and maintenance of the device are minimal, its size, as with other dewatering devices, limits its applicability at remote sample sites. Nevertheless, it has proven useful for sample collection in studies involving microbial transport and analysis of particle-associated trace inorganic solutes.

Journal of Environmental Quality↗

Aquifer response to stream-stage and recharge variations. I. Analytical step-response functions

Laplace transform step-response functions are presented for various homogeneous confined and leaky aquifer types and for anisotropic, homogeneous unconfined aquifers interacting with perennial streams. Flow is one-dimensional, perpendicular to the stream in the confined and leaky aquifers, and two-dimensional in a plane perpendicular to the stream in the water-table aquifers. The stream is assumed to penetrate the full thickness of the aquifer. The aquifers may be semi-infinite or finite in width and may or may not be bounded at the stream by a semipervious streambank. The solutions are presented in a unified manner so that mathematical relations among the various aquifer configurations are clearly demonstrated. The Laplace transform solutions are inverted numerically to obtain the real-time step-response functions for use in the convolution (or superposition) integral. To maintain linearity in the case of unconfined aquifers, fluctuations in the elevation of the water table are assumed to be small relative to the saturated thickness, and vertical flow into or out of the zone above the water table is assumed to occur instantaneously. Effects of hysteresis in the moisture distribution above the water table are therefore neglected. Graphical comparisons of the new solutions are made with known closed-form solutions.Laplace transform step-response functions are presented for various homogeneous confined and leaky aquifer types and for anisotropic, homogeneous unconfined aquifers interacting with perennial streams. Flow is one-dimensional, perpendicular to the stream in the confined and leaky aquifers, and two-dimensional in a plane perpendicular to the stream in the water-table aquifers. The stream is assumed to penetrate the full thickness of the aquifer. The aquifers may be semi-infinite or finite in width and may or may not be bounded at the stream by a semipervious streambank. The solutions are presented in a unified manner so that mathematical relations among the various aquifer configurations are clearly demonstrated. The Laplace transform solutions are inverted numerically to obtain the real-time step-response functions for use in the convolution (or superposition) integral. To maintain linearity in the case of unconfined aquifers, fluctuations in the elevation of the water table are assumed to be small relative to the saturated thickness, and vertical flow into or out of the zone above the water table is assumed to occur instantaneously. Effects of hysteresis in the moisture distribution above the water table are therefore neglected. Graphical comparisons of the new solutions are made with known closed-form solutions.

Journal of Hydrology↗

Loss of nitrogenous dissolved organic matter from small lakes

To determine how much organic nitrogen is lost from lakes during winter by natural processes, we collected water in fall and winter from six small lakes (area, 5-822 hectares) and separated organic matter dissolved in the water with n-butanol into three fractions--yellow organic acids, a white precipitate, and aqueous (nonextractable) organic matter. The nitrogen content of each fraction was measured by ultraviolet photolysis. About 25-30% of the yellow acid and white precipitate fractions were lost from the water column in each of the lakes during winter. More than 80% of the organic nitrogen dissolved in the lake water samples was found in the aqueous fraction. We believe the white precipitate is part of the humin material in lake waters because it was relatively insoluble in acidic and alkaline solutions.

Journal of Freshwater Ecology↗

Adsorption and desorption of hexavalent chromium in an alluvial aquifer near Telluride, Colorado

A laboratory investigation of reactions between hexavalent chromium [Cr(VI)] and alluvium was conducted to evaluate reactions of Cr(VI) contaminating an alluvial aquifer near Telluride, CO and to determine the mechanisms responsible for these reactions. Uncontaminated alluvium and groundwater (spiked with CrO 4 2− ) from the study site were used in batch and column experiments. Results of these experiments show that Cr(VI) was adsorbed by the alluvium. Distribution coefficients from batch experiments ranged from 52 L/kg at an equilibrium CrO 4 2− concentration of 0.4 µ mol/L to 1.7 L/kg at an equilibrium concentration of 1400 µ mol/L. The zero point of charge for the alluvium was approximately 8.3, and the alluvium had a positive net charge at the groundwater pH of 6.8. Visual and chemical evidence indicated that Fe oxide and hydroxide coatings on the alluvial particles principally were responsible for the adsorption of Cr(VI). During column experiments, Cr(VI) initially was desorbed easily from the alluvium by Cr‐free groundwater; however, the rate of desorption decreased rapidly, and > 60 pore volumes of groundwater were required to decrease the effluent concentration of Cr(VI) to 3 µ mol/L [drinking water standard for Cr(VI) = 1 µ mol/L]. The quantity of Cr(VI) adsorbed varied with the type and concentration of other anions in solution.

Colorado↗