3,452 research outputs found
The Geochemistry of Stream Sediments, Chagres River, Panama: Weathering in a Tropical Watershed
No full textChemical weathering of the earth’s surface is a primary process controlling landscape and soil development as well as the geochemistry of natural waters. In addition, chemical weathering of silicate minerals, which consumes atmospheric CO2, is a major control of long term climate variation. Although much has been published related to the rates and intensities of chemical weathering, very little data exist on chemical weathering in mountainous tropical regions.
The Chagres River is considered Panama’s most important river with a total runoff of 4.4x105 m3 per year during years of higher flow. The highest areas of the watershed rise to elevations of 275m. The high rainfall, warm temperatures (mean annual T° of ~19°C) and steep topography all increase rates of chemical weathering in the watershed relative to more temperate locations. In this study I will analyze a series of stream sediment samples from the Chagres River with the purpose of establishing the intensity of chemical weathering in this environment. These samples will be analyzed for both major and trace element composition and compared to the geochemistry of the surrounding bedrock lithologies as well as the upper continental crustal average where data are available. The data from these Panamanian sediments will be compared to other high rainfall mountainous regions in more temperate climates, such as Taiwan and New Zealand, to determine the relative intensity of weathering within the Chagres basin.
In addition to the sediment samples analyzed by me, I have compiled and interpreted a set of river samples that have been analyzed for dissolved silica (Si) by Dr. Lyons’ group at The Byrd Polar Research Center. Si is a major dissolved component of the chemical weathering of silicate minerals. The dissolved Si data will be normalized to chloride (Cl) in order to account for rainwater input, evaporation and evapo-transpiration so that the spatial locations of enhanced weathering (i.e. Si increase in the stream water) can be detected. These data are used to better confine the lithologic sources of more concentrated silicate mineral weathering within the watershed
Sex Addiction: the Chicken-and-Egg Dilemma of Diagnosis
No full textIn May 2013, the American Psychiatric Association will release the next version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V). Interestingly, sex addiction, despite significant attention from mainstream media, will be omitted from the manual. This omission presents a challenge to clinicians who treat sex addiction, and researchers aiming to further our understanding of the issue. This commentary outlines some of the reasons sex addiction was not included in the DSM-V, including a ‘chicken-and-egg’ conundrum, which makes it difficult to generate research without a clear diagnosis, and difficult to establish a definitive diagnosis without a supportive body of research
Letter from George W. Kimball, Tusayan National Forest, to Carl Hayden
No full textLetter from George W. Kimball to Carl Hayden with an enclosed map detailing the cattle and sheep allotments on the portion of the Tusyan Forest next to the Grand Canyon. Listed are names of permit holders in both stock and allotment that are most likely to trespass into the park. The names are: W. F. Griffin, W. W. Bass, H. R. Lauzon, Swanner and Griffin, Bankhead and Henderson, Martin Buggeln, Babbitt Brothers, Sanford Rowe, and P. D. Berry
Microbial diversity of an Antarctic subglacial community and high-resolution replicate sampling inform hydrological connectivity in a polar desert
No full textAntarctic subglacial environments host microbial ecosystems and are proving to be geochemically and biologically diverse. The Taylor Glacier, Antarctica, periodically expels iron-rich brine through a conduit sourced from a deep subglacial aquifer, creating a dramatic red surface feature known as Blood Falls. We used Illumina MiSeq sequencing to describe the core microbiome of this subglacial brine and identified previously undetected but abundant groups including the candidate bacterial phylum Atribacteria and archaeal phylum Pacearchaeota. Our work represents the first microbial characterization of samples collected from within a glacier using a melt probe, and the only Antarctic subglacial aquatic environment that, to date, has been sampled twice. A comparative analysis showed the brine community to be stable at the operational taxonomic unit level of 99% identity over a decade. Higher resolution sequencing enabled deconvolution of the microbiome of subglacial brine from mixtures of materials collected at the glacier surface. Diversity patterns between this brine and samples from the surrounding landscape provide insight into the hydrological connectivity of subglacial fluids to the surface polar desert environment. Understanding subice brines collected on the surfaces of thick ice covers has implications for analyses of expelled materials that may be sampled on icy extraterrestrial worlds
Analysis of Acid-Leachable Barium, Copper, Iron, Lead, and Zinc Concentrations in Taylor Valley, Antarctic Stream Sediments
No full textThe purpose of this study is to assess the concentrations of Barium (Ba), Copper (Cu), Iron (Fe), Lead (Pb), and Zinc (Zn) in sediment samples obtained from the Wales and Commonwealth streams located in Taylor Valley, Antarctica. These samples were collected at seven sample sites (three in Wales Glacier and four in Commonwealth Glacier) in 0 to 2 cm, 2 to 4 cm, 4 to 6 cm, and 6 to 8cm depth increments which resulted in 28 total samples. After the collection process, these samples underwent a volumetric 1:5 sediment: 10% HCl leach for 48 hours, filtration through 4-µm pore-size, cellulose acetate membrane filters, and inductively coupled plasma mass spectrometry (ICP-MS) analyses in the Trace Element Research Laboratory at The Ohio State University. Upon completion of the analyses, results showed that the Wales samples had a higher average concentration of every metal element overall and at each depth increment when compared to the Commonwealth samples. In addition to the weak-acid leachate metal analyses, a second aliquot of one sediment profile from each stream was analyzed at Villanova University for the 210Pb activity via gamma spectroscopy. This was done to estimate the sedimentation rates at each of these sites. From the sedimentation rates, sedimentation fluxes were calculated for each element for each sediment profile at each of these sites. The data demonstrated that Fe is the most abundant element while Pb is the least abundant. Lastly, upon examination of results, it was found that the concentrations of these metals are often higher in samples collected closer to the surface. These findings suggest these streams, and their sources, have had little, if any, impact by anthropogenic input of metals, and that metal fluxes to the sediments are low.NSF OPP 1115245Byrd Polar and Climate Research Center McKenzie-Brecher ScholarshipNo embargoAcademic Major: Earth Science
Comparing the Weathering Environment of Permian and Modern Antarctic Proglacial Lake Sediments: Mineralogical and Geochemical Study
No full textThe Antarctic continent has been in a polar to subpolar position since the Permian period. Although it has experienced milder climates over this time period as evidenced by corals in the fossil record, Antarctica did undergo extensive glaciation during the Permian. This is based on the abundance of Permian tillites (sedimentary rocks derived from glacier tills) found in the Transantarctic Mountains. In this research, I have compared Permian age proglacial lake sediments that are associated with tilites to modern proglacial lake siltstones and mudstones from Antarctica. This was done to determine the climate, especially the amount of glacier melt that occurred when these Permian sediments were deposited. The modern lake sediments are deposited in perennially ice-covered lakes by ephemeral streams that only flow 6 to 12 weeks a year. The geochemical analyses of the Permian samples and the modern sediments from Lake Hoare in the McMurdo Dry Valleys suggest that the Permian samples are more highly chemically weathered than the modern sediments. The mineralogy of Lake Hoare sediments contain more primary minerals than chemical weathering produced minerals in the Pagoda Formation rocks, thus supporting the geochemical analysis that the Pagoda Formation minerals have been more weathered. All these data suggest that the Permian lake samples were deposited in a warmer, more hydrogeologically active environment than were the modern lake sediments. These data support previously published sedimentological and paleontological data that the Pagoda samples were deposited under more temperate or warm-based proglacial conditions than what is observed in the McMurdo Dry Valleys today.No embargoAcademic Major: Earth Science
Evaluating Anthropogenic Impact on Water Quality of Ohio Rivers Over Time
No full textMany natural and anthropogenic factors affect the geochemistry of surface waters like rivers and streams in rural and urban areas. Much impact on fresh water in the United States comes from non-point sources, with population and land use playing an important role. Major components of input into surface waters are chloride and sodium, derived mostly from urban contributions such as road salt, and nitrate, largely from agricultural sources like fertilizers, as well as the burning of fossil fuels. Fresh water quality historical data exists for many Ohio rivers, however much of it has never been further utilized to observe ion concentration trends over past decades.
I have tabulated past data from state and federal sources such as USGS and data from Dr. Lyon’s research group from the 2000’s to identify long-term trends in ion concentrations in rivers at multiple locations throughout the greater Columbus area. In June, I sampled the same sites examined in the past and analyzed the filtered samples for major ions and nutrients. By comparing the summer 2012 samples to those from same sites in the past, the magnitude of the effects of urban and rural contributions on surface runoff and fresh water quality will be determined.Shell Exploration and Production Company 2012No embarg
The geochemistry of stream sediments, Panama: weathering in a tropical watershed
No full textChemical weathering of Earth's surface is the primary process controlling landscape and soil development, as well as the geochemistry of natural waters. In addition, chemical weathering of silicate minerals, which consumes atmospheric C02, is a major control of long-term climate variation. Although much has been published related to the rates and intensities of chemical weathering for temperate and high-latitude settings, few data exist on chemical weathering in mountainous tropical regions. This study focuses on the Rio Chagres watershed. The Rio Chagres is one of Panama's most important rivers. This 414 krn2 watershed produces a total runoff of 4.4xl 05 m3 per year during years of higher flow, supplying almost half the water required to operate the Panama Canal. The highest areas of the watershed rise to elevations of 1000m. The high rainfall (c.2000mm/yr), warm temperatures (mean annual T° ~ 19°C), and steep forested topography all increase rates of chemical weathering in the watersheds relative to more temperate geographic settings. Samples have been analyzed for the purpose of establishing the intensity of chemical weathering in this environment using X-Ray Fluorescence Spectroscopic (XRF) techniques for both major and trace element composition. Stream sediment geochemistry has been compared to the geochemistry of local bedrock lithologies and normalized to upper continental crust values. XRF analyses of sediments from the Rio Chagres headwaters demonstrate depletion in Ca2+, Sr2+, Ba2+, K+ and Rb+ relative to average upper continental crust, suggesting rapid loss of these elements. Grain-size analyses of the stream sediments suggest there is a positive relationship between sediment size, the rate of chemical weathering and the watershed geology. Watersheds draining mostly altered volcanic lithologies have mainly sand-size sediments by comparison to watersheds draining mainly intrusive mafic lithologies which tend to have coarser sediments. These data, combined with previously reported water geochemical data, suggest intensive weathering of the altered volcanic lithologies and that the intrusive mafic lithologies are not being weathered at the same rate or intensity as the volcanic lithologies.No embarg
Qualitative estimate of recharge in an unconsolidated glacial aquifer in Fulton County, Ohio
No full textCan High-Altitude Ice Masses in Temperate Areas Provide Useful Climatic Records?
No full textSince 1979 we have been conducting a program of glaciochemical sampling and analysis in selected portions of the Indian Himalayas. The primary purpose of this work has been the retrieval of data that are of specific use in assessing the signal expressed by the chemistry of air masses entering the Himalayas. The techniques used for this purpose provide data sets for the following: chloride, sodium, reactive iron, reactive silicate, reactive phosphate, nitrite-plus-nitrate, ammonium, pH, oxygen isotopes, deuterium, microparticles, total β-activity, density and scanning electron microscopy. The results of this work appear in a series of papers (Lyons and others 1981, Lyons and Mayewski 1983, Mayewski and others 1981, 1983, 1984 and Goss and others 1985). In summary this work demonstrates: (1) problems encountered in high-altitude ice-core recovery, (2) effects of percolation on chemical records, (3) specific requirements necessary for the retrieval of unaltered glaciochemical records from Himalayan glaciers, (4) potential spatial variability of chemical species concentrations and interpretation of this with respect to time series, (5) usefulness of various glaciochemical indicators as applied to relative dating (seasonality) and air mass tracking, (6) specific details of the chemical and physical properties in Himalayan ice, and (7) recommendations for future Himalayan ice-core studies.</jats:p
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