29 Search Results

The effectiveness of laser-induced nuclear orientation in the study of short-lived unstable nuclei using radiation detection has been increased by the use of saturation spectroscopy to produce sub-Doppler resolved changes in the anisotropic spatial distribution of the 514-keV gamma rays from the 1 - mu-s isomer Rb(85m). The width (HWHM) of these change signals is about 60 MHz, a factor of ten better than Doppler-broadened signals previously obtained. This technique has been used to study the D1 and D2 transitions for the isomer. Precise values of the hyperfine A and B coefficients have been determined, and used to extract a value for the nuclear magnetic dipole moment (6.043 + or - .005) mu sub N, and, for the first time, a measured value of the nuclear quadrupole moment (-.73 + or - .17)b. Additionally, and a new, more accurate value for the isomer shift (-113 + or - 5)MHz has been determined.

Measurements were made in mud-flat sediments from Flax Pond salt marsh to characterize the rates and mechanisms of sulfur cycling in an organic-rich coastal marine environment. Approximately 13 mmoles/m{sup 2} of reduced sulfur are generated annually in the mud flat and the dominant solid-phase product is pyrite. Ion activity products involving dissolved iron and sulfide species indicate approximate saturation with respect to metastable iron sulfide phases, showing that pyrite is not likely to be the first-formed Fe-bearing sulfide. Comparison of {Sigma}H{sub 2}S vs. SO{sup =}{sub 4} relationships in anoxic incubation experiments with those occurring in the undisturbed sediment permits evaluation of possible mechanisms involved in the transformation of metastable iron monosulfides to pyrite. Oxidants (e.g. MnO{sub 2}) that are introduced into the surface sediment, either by animal activity or physical events, are apparently necessary to cause major oxidation of FeS and {Sigma}H{sub 2}S to pyrite and sulfate. Solid-phase sulfur analyses and net {Sigma}H{sub 2}S accumulation in sediment pore waters are consistent with major sulfide oxidation, indicating that approximately 95% of the sulfide generated in the mud flat is reoxidized to sulfate and roughly half of this oxidation involves dissolved sulfide. The major factors limiting reduced sulfur burial are physical and biological disturbances and a low abundance of reactive solid-phase iron (2 wt%).

Recent research asked the question: Why do some people make home energy conservation a priority while others ignore it In order to answer this question, a residential energy conservation survey was conducted in 220 households from varying locations and social groups. The single most important factor for employing energy conservation measures in the home was the completion of a home energy audit. Home energy audits are offered by many utility companies at no cost to the consumer. Other factors found to be significant were age, with the middle-aged households the most energy conscious, and income, with the lower income households more likely to make changes in order to save money.

Hazardous wastes are everywhere, including the average American household.Some cleaners, automobile products, pesticides and paint products can be potentially hazardous substances. Such products may contain solvents, petroleum products, heavy metals, or other toxic chemicals. Chemicals found in the kitchen, bathroom, garage, garden shed to workshop can poison, corrode, explode, or burst into flames if improperly handled. If improperly discarded, they can injure people and pollute the environment. The author then lists the major classes of household wastes and outlines their proper use, storage, and disposal.

Sedimentary solute distributions and fluxes are determined in part by the kinetics of production/consumption reactions in a deposit. It is possible to estimate rates and investigate kinetic relations in undisturbed or manipulated sediments by documenting build-up or depletion patterns of solutes allowed to diffuse either between relatively thin sections of sediment and a well-stirred water reservoir or through a large section of sediment without an overlying reservoir. The time-dependent concentrations in the sediment in both cases depend on reaction rates, kinetics, diffusion coefficients, and geometric scaling of the sediment and contacting reservoir. The water reservoir size and sediment thickness can be altered to allow rapid estimates of reaction rates at near steady-state or to examine nonsteady-state behavior. Nonsteady-state models are always required for the whole-core incubation method, which has the advantages that it is less labor-intensive than many other rate measurement methods and the incubations can be performed in situ. Experimental comparisons between open-incubation and more traditional closed-incubation estimates of reaction rates show good agreement for solutes such as HN{sub 4}(+), SO4(--), HPO{sub 4}(-) and I(-). In some cases, e.g., Mn(++), Fe(++), and HPO{sub 4}(-) production, where major back-reactions with sediment occur, open-incubations without substantial build-up of solutes may provide the most accurate method for estimating production rates. In principle, the open incubation methods described can be used for any diffusable species. 31 refs., 19 figs., 1 tab.

Using laser-induced nuclear-orientation and optical-saturation techniques, we have produced sub-Doppler changes in the anisotropy of the angular distribution of the 514-keV {gamma} rays from the 1-{mu}s isomer {sup 85}Rb{sup {ital m}}. This permits high-resolution measurements of {ital D}1 and {ital D}2 hyperfine transitions of atoms of the isomer, which give the isomer's nuclear electric quadrupole moment, {minus}0.73{plus minus}0.17 b, and its nuclear magnetic dipole moment, (6.043{plus minus}0.005){mu}{sub {ital N}}. The isomer shift, {minus}113{plus minus}8 MHz relative to the ground state of {sup 85}Rb, corresponds to a change in the mean-square charge radius of +0.174{plus minus}0.008 fm{sup 2}.

The present investigation tests a model to explain the behavior of dissolved Si during early diagenesis in sediments. The model assumes that low-Fe clays and other minerals can be treated simply as Al hydroxides, having attached silica. When the minerals are placed in seawater solutions, Si is released, causing exposure of fresh Al-octahedra, which are reactive toward Si and other elements in solution. Standard clays (kaolinite, montmorillonite) and solid silicic acid were suspended in seawater solutions in various combinations, and dissolved Al, Si, Ca, pH and alkalinity were determined as a function of time. The theoretical model correctly predicts the behavior of Si in mixtures of the different minerals, based upon the dissolution behavior of the minerals in suspension alone. Further, the decrease in the alkalinity of kaolinite-containing seawater solutions, where carbonate dissolution, organic matter decomposition and reduced sulfur oxidation are apparently unimportant, can be predicted from a simple extrapolation of the silica model results. The alkalinity changes observed in this study, as well as the pH changes observed in standard clay suspensions by other researchers, can be explained simply by equilibration of the charge on exposed Al-octahedra with the pH of the surrounding waters. The results of this study indicate that theoretical models of Si diagenesis in sediments should have general usefulness for predicting the effects of clay dissolution on sediment properties.

Particulate and dissolved phase concentrations of heavy metals (Fe, Mn, Cu, and Ni) and organic carbon were determined in surface microlayer and subsurface (1m) samples collected in the vicinity of a river plume. Observed variations in dissolved Ni and Mn concentrations are attributed to mixing between river and lake waters. Heavy metal concentrations in the particulate organic carbon show a progressive decrease between the river mouth, a down-plume station, and the open lake area outside the river plume. These trends are due to segregation between mineralized and organic particulates as well as differential transport of different mineralogical groups. The pronounced influence that these physical processes have on the composition of the surface microlayer raised a serious doubt concerning our ability to identify compositional variations due to strictly chemical processes within the microlayer.

Principal environmental problem areas of importance to the Department of Defense were identified and possible approaches to advanced research projects directed toward solutions of these problems were suggested to provide partial source material in support of ARPA's research program planning. Topics regarding environmentsl impact analysis, resources management, air quality, water quality, materials handling and disposal, data management, and special problems were included. For each topic, information was organized according to statement of the problem, state of the art, present activities and organization, implications for the DoD, and recommendations for further studies. (GRA)

Natural seawater was required for use in experiments designed to determine the dissolution rate of certain nuclear fuel materials. A method was devised for the collection, storage, and analysis of the water. The method stipulates: off-shore collection of surface water in polyethylene carboys, which are subsequently stored, at a reduced temperature, in a dark location; and monitoring biological and chemical composition via microfiltration, chlorinity, oxygen, alkalinity, phosphate, and nitrate analyses. (auth)