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2007

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Articles 421 - 450 of 537

Full-Text Articles in Earth Sciences

Carbonated Sections From Komatiite Flow- Top Alteration Zones In The Barberton Greenstone Belt: Implications For Near-Surface Archean Environments, Judith E. F. Stoute Jan 2007

Carbonated Sections From Komatiite Flow- Top Alteration Zones In The Barberton Greenstone Belt: Implications For Near-Surface Archean Environments, Judith E. F. Stoute

LSU Master's Theses

Over a dozen komatiitic flows in the 3.2-3.5 Ga Barberton Greenstone Belt are topped with unique green silica- and carbonate-rich rocks, which likely formed from interaction of the cooling lava flow with seawater shortly after deposition. This study focuses on an alteration zone in the Mendon Formation. Two styles of alteration are observed in this alteration zone: silicification and carbonation. The goal of this study is to characterize the carbonates in the alteration zone, constrain the timing of alteration, test whether the alteration zones are due to interaction with seawater after deposition, and estimate the elemental fluxes between the rock …


Farm Water For The North-Eastern And Eastern Wheatbelt Of Western Australia (Zones 2 And 5), Susan Murphy-White Jan 2007

Farm Water For The North-Eastern And Eastern Wheatbelt Of Western Australia (Zones 2 And 5), Susan Murphy-White

Resource management technical reports

Large proportions of Western Australia's dryland farms suffer from water supply problems in the form of shortages, poor quality or combinations of these two factors ... A regional study for the North-eastern and Eastern Wheatbelt of Western Australia was undertaken. The base data used to develop water supply areas included soil type, landscape units, geology, hydrogeology, native vegetation and existing far water resource infrastructure.


Observation Of Microslip Dynamics At High-Speed Microcontacts, Brian Borovsky, Adam M. Booth, Erin Manlove Jan 2007

Observation Of Microslip Dynamics At High-Speed Microcontacts, Brian Borovsky, Adam M. Booth, Erin Manlove

Geology Faculty Publications and Presentations

The high-speed tribological properties of microscale contacts are studied using an indenter probe and quartz crystal microbalance. Elastic and dissipative shear forces are monitored as a function of contact radius for sapphire/gold interfaces with an adsorbed octadecanethiol monolayer. We observe shear force transitions understood as taking the interface from slipping to stuck conditions. We relate this behavior to the presence of interfacial microslip. Dynamic modeling shows that our observations are consistent with an interface that, when sliding, experiences full slip during half of each cycle. We discuss the implications for this technique as a sensitive probe of sliding friction.


Paleoceanography Of The Gulf Of Papua Using Multiple Geophysical And Micropaleontological Proxies, Lawrence A. Febo Jan 2007

Paleoceanography Of The Gulf Of Papua Using Multiple Geophysical And Micropaleontological Proxies, Lawrence A. Febo

LSU Doctoral Dissertations

Recent marine and late Pleistocene sediments examined from the Gulf of Papua (GoP), Papua New Guinea investigate the flux and fate of detrital sediments and organic carbon over the last glacial-interglacial cycle. Based on surface sediment magnetic susceptibility (MS) and calcium carbonate concentrations, recent marine sediment is exported off the narrow shelf and into deeper regions via the Kerema Canyon of the northern Pandora Trough. Detrital clastic sediment is then dispersed deeper into the central and southern Pandora Trough. Except for pelagic deposition, very little detrital material reaches the Ashmore Trough and Eastern Plateau adjacent to the Great Barrier Reef. …


Biogeochemical Processes And Seasonal Effects In Flow-Through Mesocosm Reactors Simulating Constructed Wetlands, Sarah J. Tritschler Jan 2007

Biogeochemical Processes And Seasonal Effects In Flow-Through Mesocosm Reactors Simulating Constructed Wetlands, Sarah J. Tritschler

Browse all Theses and Dissertations

Due to their distinctive environments, constructed wetlands are utilized to remediate groundwater that has been contaminated with chlorinated ethenes (i.e. perchloroethene) and other such contaminants. This research focuses on vertical flow mesocosm reactors housed in a greenhouse at Wright State University, which simulate a constructed wetland on Wright-Patterson Air Force Base. These reactors were studied to investigate the effects of vegetation and seasonal changes on the redox parameters present. Water samples were collected from six different reactors from late September/early October 2006 until August 2007. The reactors were sampled three days in a row and this sampling was done once …


The Environmental Implications Of Aggradation In Major Braided Rivers At Mount Rainier National Park, Washington, Scott Robert Beason Jan 2007

The Environmental Implications Of Aggradation In Major Braided Rivers At Mount Rainier National Park, Washington, Scott Robert Beason

Dissertations and Theses @ UNI

The purpose of this study is to quantify the historic rate of river bed filling, and to the extent possible, evaluate the factors that control sedimentation in river channels at Mount Rainier National Park. Mount Rainier is the tallest and the most glaciated of the Cascade volcanoes, located in southwestern Washington State. Steep, glacially-fed braided rivers radiate outward from the volcano in all directions and transport materials varying from fine sediment to cobbles and large boulders. As the gradient in the channels decreases downstream, sediment is no longer entrained and accumulates in the river bed. Over time, the river bed …


Annual Pasture Legume Options For Key Soil Types, Department Of Agriculture, Western Australia, Grains Research & Development Corporation Jan 2007

Annual Pasture Legume Options For Key Soil Types, Department Of Agriculture, Western Australia, Grains Research & Development Corporation

All other publications

No abstract provided.


Evidence Of A Pre-Mount Simon, Half-Graben In Greene County, Ohio By Reprocessing A Wright State University Seismic Line, John Sink Jan 2007

Evidence Of A Pre-Mount Simon, Half-Graben In Greene County, Ohio By Reprocessing A Wright State University Seismic Line, John Sink

Browse all Theses and Dissertations

The reprocessing of the WSU2002 seismic line indicates the presence of a Precambrian half-graben. Also observed through this reprocessing is the possible presence of Paleozoic structures. Although Paleozoic features have been interpreted, variations in glacial drift thickness evidenced by glacial drift maps also may have contributed to a lower quality of stacked section in comparison to other seismic lines. WSU2002 was originally processed by Lauren Geophysical. The Lauren processing resulted in an image that was of much lower quality than corresponding seismic lines. The Lauren Geophysical processed section revealed many horizontal Paleozoic reflections, with no prominent reflectors beneath the Paleozoic. …


Geophysical Reconnaissance Of Karst Features Associated With Sinkholes On The Antioch University Campus In Yellow Springs, Ohio: Western Area, Brent Matthew Zerkel Jan 2007

Geophysical Reconnaissance Of Karst Features Associated With Sinkholes On The Antioch University Campus In Yellow Springs, Ohio: Western Area, Brent Matthew Zerkel

Browse all Theses and Dissertations

Antioch University is located in Yellow Springs, OH. This study was conducted on the Antioch University Campus in the commons area and is concentrated on the area west of the easternmost sinkhole. The primary purpose of this study is to locate and identify buried anomalous karst features, such as joints and collapses that may be hazardous to nearby buildings on the Antioch University Campus. The secondary purposes of this study are to identify remaining features in the geophysical data that may be related to manmade structures, and to identify areas for future studies. It is known that an 8-inch steel …


Seasonal Variation In The Redox Zones And Biogeochemical Processes Within The Constructed Wetland, Yussuf Mohamud Jan 2007

Seasonal Variation In The Redox Zones And Biogeochemical Processes Within The Constructed Wetland, Yussuf Mohamud

Browse all Theses and Dissertations

This research investigation focuses on the vertical distribution of dissolved inorganic species in the pore-water affected by redox processes and seasonal changes within a small constructed wetland located at the Wright-Patterson Air Force Base. This is a follow up study to an earlier investigation (Lach, 2004) at this site in 2003. Water samples were collected from influent, effluent and three layers of the constructed wetland through a network of nested piezometers in the vertical flow wetland from June 2005 to June 2006. Onsite analysis of temperature, pH and conductivity were carried out onsite. Major anions and cations were measured by …


Impact Of Land Use On Water Quality In The Indian Lake Watershed: An Integrated Geographic Information Systems Approach, Michael Belke Jan 2007

Impact Of Land Use On Water Quality In The Indian Lake Watershed: An Integrated Geographic Information Systems Approach, Michael Belke

Browse all Theses and Dissertations

Geology and land use and land cover are the most important factors that influence water quality. The purpose of this study is to investigate how these factors operate in a rural watershed. Specifically, this thesis tests the feasibility of a proposed formula to relate how land use affects surface water quality and to infer hydrogeochemical reactions that control water chemistry through hydrogeochemical speciation and mineral stability relationships. Samples were collected from Indian Lake and its watershed in West-Central Ohio. BASINS, produced by the USEPA, was then used to delineate sub-watersheds and find the land use areas of these watersheds. The …


Origin Of Kaolin Deposits: Evidence From The Hisarcık (Emet-Kütahya) Deposits, Western Turkey, Ali̇ Sayin Jan 2007

Origin Of Kaolin Deposits: Evidence From The Hisarcık (Emet-Kütahya) Deposits, Western Turkey, Ali̇ Sayin

Turkish Journal of Earth Sciences

Kaolin deposits, situated approximately 20 km south of Hisarcık, have been formed by the alteration of dacite and dacitic tuffs related to the Miocene volcanism associated with extensional tectonics. The Hisarcık kaolin deposits occur in the Kızılcukur, Ulaşlar and Kurtdere areas. Kaolinite is the only clay mineral associated with a-quartz, K-feldspar, plagioclase, alunite, natroalunite and hematite in some kaolins, whereas, other kaolinite accompanies smectite, which represents a moderate kaolinization. Low-cristobalite is the dominant silica mineral in these kaolins. In spite of strong kaolinization, the kaolins contain a high amount of finely-disseminated a-quartz in places, resulting in low Al_2O_3 values (13.80 …


Intracontinental Quaternary Volcanism In The Niksar Pull-Apart Basin, North Anatolian Fault Zone, Turkey, Orhan Tatar, Sema Yurtmen, Haluk Temi̇z, Hali̇l Gürsoy, Fi̇kret Koçbulut, B. Levent Mesci̇, Jean Claude Guezou Jan 2007

Intracontinental Quaternary Volcanism In The Niksar Pull-Apart Basin, North Anatolian Fault Zone, Turkey, Orhan Tatar, Sema Yurtmen, Haluk Temi̇z, Hali̇l Gürsoy, Fi̇kret Koçbulut, B. Levent Mesci̇, Jean Claude Guezou

Turkish Journal of Earth Sciences

The Niksar Basin is sited along the eastern segment of the North Anatolian Fault Zone in Turkey. It is a young sigmoidal pull-apart basin bordered by two non-parallel master faults associated with earthquakes in 1939 and 1942. The fault geometry along the irregular ENE margin of the basin is complex where young Plio-Quaternary volcanic rocks reach the surface along pairs of steep strike-slip faults which cut the basin sediments. The volcanic rocks around the Niksar Basin have been dated by high precision K-Ar dating and the ages range between 542 ± 9 ka and 567 ± 9 ka. The lavas …


Petrographic And Geochemical Study On Cave Pearls From Kanaan Cave (Lebanon), Fadi H. Nader Jan 2007

Petrographic And Geochemical Study On Cave Pearls From Kanaan Cave (Lebanon), Fadi H. Nader

International Journal of Speleology

The Kanaan cave is situated at the coastal zone, north of Beirut City (capital of Lebanon). The cave is located within the upper part of the Jurassic Kesrouane Formation (Liassic to Oxfordian) which consists mainly of micritic limestone. Twenty seven cave pearls were subjected to petrographic (conventional and scanning electron microscopy) and geochemical analyses (major/trace elements and stable isotopes). The cave pearls were found in an agitated splash-pool with low mud content. They are believed to have formed through chemical precipitation of calcite in water over-saturated with calcium. The nucleus and micritic laminae show δ18OV-PDB values of …


Seasonal Variations Of Co2 And 222Rn In A Mediterranean Sinkhole - Spring (Causse D’Aumelas, Se France), Christelle Batiot-Guilhe, Jean-Luc Seidel, Hervé Jourde, Olivier Hébrard, Vincent Bailly-Comte Jan 2007

Seasonal Variations Of Co2 And 222Rn In A Mediterranean Sinkhole - Spring (Causse D’Aumelas, Se France), Christelle Batiot-Guilhe, Jean-Luc Seidel, Hervé Jourde, Olivier Hébrard, Vincent Bailly-Comte

International Journal of Speleology

Carbon dioxide and 222Rn monitoring of the atmosphere of a Mediterranean sink hole - spring (SE France) during two hydrological cycles (from September 2004 to September 2006) showed seasonal variations with very high concentrations during summer (greater than 6% and 20 000 Bq/m3, respectively). Gas dynamics in caves often show seasonal variations. Meteorological parameters (barometric pressure and temperature mainly), cave geometry and fracture networks control exchanges between the cavity and outside atmosphere. Carbon dioxide and 222Rn may have different sources (atmosphere, soil, bedrock, deep gas diffusion, in situ oxidation of organic matter and, in some caves, …


The Impact Of Host Rock Geochemistry On Bacterial Community Structure In Oligotrophic Cave Environments, Hazel A. Barton, Nicholas M. Taylor, Michael P. Kreate, Austin C. Springer, Stuart A. Oehrle, Janet L. Bertog Jan 2007

The Impact Of Host Rock Geochemistry On Bacterial Community Structure In Oligotrophic Cave Environments, Hazel A. Barton, Nicholas M. Taylor, Michael P. Kreate, Austin C. Springer, Stuart A. Oehrle, Janet L. Bertog

International Journal of Speleology

Despite extremely starved conditions, caves contain surprisingly diverse microbial communities. Our research is geared toward understanding what ecosystems drivers are responsible for this high diversity. To asses the effect of rock fabric and mineralogy, we carried out a comparative geomicrobiology study within Carlsbad Cavern, New Mexico, USA. Samples were collected from two different geologic locations within the cave: WF1 in the Massive Member of the Capitan Formation and sF88 in the calcareous siltstones of the Yates Formation. We examined the organic content at each location using liquid chromatography mass spectroscopy and analyzed microbial community structure using molecular phylogenetic analyses. In …


Decadal Variation Of The Southwest U.S. Summer Monsoon Circulation And Rainfall In A Regional Model, Q. Steven Hu, Yongjun Zheng Jan 2007

Decadal Variation Of The Southwest U.S. Summer Monsoon Circulation And Rainfall In A Regional Model, Q. Steven Hu, Yongjun Zheng

Department of Earth and Atmospheric Sciences: Faculty Publications

Previous studies have identified several major causes for summer rainfall variations over the southwest United States, for example, land memory (i.e., relationships between antecedent winter season precipitation and snow cover anomalies and subsequent summer rainfall anomalies over the southwest United States; these anomalies are likely most important in the northwest United States, although antecedent anomalies in the southwest United States also may be important in determining summer rainfall variations) and sea surface temperature (SST) anomalies in the North Pacific. Atmospheric responses to these “boundary forces” interact with moisture flows from the Gulf of Mexico and from the Gulf of California …


San Andreas Fault Zone Mineralogy, Geochemistry, And Physical Properties From Safod Cuttings And Core, John G. Solum, Stephen Hickman, David A. Lockner, Sheryl Tembe, Jim P. Evans, Sarah D. Draper, D. C. Barton, David L. Kirschner, Judith S. Chester, Frederick M. Chester, Ben A. Van Der Pluijm, Anja M. Schleicher, Diane E. Moore, Carolyn Morrow, Kelly Bradbury, Wendy M. Calvin, Teng-Fong Wong Jan 2007

San Andreas Fault Zone Mineralogy, Geochemistry, And Physical Properties From Safod Cuttings And Core, John G. Solum, Stephen Hickman, David A. Lockner, Sheryl Tembe, Jim P. Evans, Sarah D. Draper, D. C. Barton, David L. Kirschner, Judith S. Chester, Frederick M. Chester, Ben A. Van Der Pluijm, Anja M. Schleicher, Diane E. Moore, Carolyn Morrow, Kelly Bradbury, Wendy M. Calvin, Teng-Fong Wong

United States Geological Survey: Staff Publications

The San Andreas Fault Observatory at Depth (SAFOD), drilled near the town of Parkfield, California (Fig. 1) (Hickmen et al., 2004) as part of the U.S. National Science Foundation's EarthScope Project (see http://www.earthscope.org), provieds a continuous set of samples through the active San Andreas Fault (SAF) zone. These samples can help address decades-old questions such as apparent weakness of the SAF (Zoback, 2000) providing the unparalleled opportunity to contrain the parameters that control the behavior of plate counding faults like the San Andreas.

Samples collected form SAFOD also complement studies of exhumed fault zones. While studies of exhumed fault zones …


Factors Influencing Ground-Water Recharge In The Eastern United States, Bernard T. Nolan, Richard W. Healy, Patrick E. Taber, Kimberlie Perkins, Kerie J. Hitt, David M. Wolock Jan 2007

Factors Influencing Ground-Water Recharge In The Eastern United States, Bernard T. Nolan, Richard W. Healy, Patrick E. Taber, Kimberlie Perkins, Kerie J. Hitt, David M. Wolock

United States Geological Survey: Staff Publications

Ground-water recharge estimates for selected locations in the eastern half of the United States were obtained by Darcian and chloride-tracer methods and compared using statistical analyses. Recharge estimates derived from unsaturated-zone (RUZC) and saturated-zone (RSZC) chloride mass balance methods are less variable (interquartile ranges or IQRs are 9.5 and 16.1 cm/yr, respectively) and more strongly correlated with climatic, hydrologic, land use, and sediment variables than Darcian estimates (IQR = 22.8 cm/yr). The unit-gradient Darcian estimates are a nonlinear function of moisture content and also reflect the uncertainty of pedotransfer functions used to estimate hydraulic parameters. Significance …


New Insights Into Marine Migration And Winter Habitat Of Gulf Sturgeon, Randy E. Edwards, Frank M. Parauka, Kenneth J. Sulak Jan 2007

New Insights Into Marine Migration And Winter Habitat Of Gulf Sturgeon, Randy E. Edwards, Frank M. Parauka, Kenneth J. Sulak

United States Geological Survey: Staff Publications

Migrations and movements of Gulf sturgeon Acipenser oxyrinchus desotoi were determined using satellite pop-up archival transmitting (PAT) tags and acoustic telemetry. Adult Gulf sturgeon from four rivers in northwestern Florida were caught with gill nets and were tagged with PAT and acoustic tags in the fall of 2001 and 2002. PAT tags were programmed to release in early February 2002 and 2003 to provide information about location of late-winter marine habitats. However, only 5 of 25 provided meaningful location information. Three of the PAT-tagged fish were relocated acoustically near the PAT tag pop-up locations, one of which was in Choctawhatchee …


Kinematics Of The Nicaraguan Forearc From Gps Geodesy, Henry L. Turner, Peter Lafemina, Armando Saballos, Glen S. Mattioli, Pamela E. Jansma, Timothy H. Dixon Jan 2007

Kinematics Of The Nicaraguan Forearc From Gps Geodesy, Henry L. Turner, Peter Lafemina, Armando Saballos, Glen S. Mattioli, Pamela E. Jansma, Timothy H. Dixon

School of Geosciences Faculty and Staff Publications

Campaign GPS data from a network in the Nicaraguan forearc show a strong component of arc-parallel motion indicating northwest translation of a nearly rigid forearc sliver. Our measured mean velocity for forearc sites of 15.1 mm yr−1 agrees well with the arc-parallel sliver motion predicted previously by DeMets (2001) derived from closure constraints on oblique convergence between the Cocos and Caribbean plates. The lack of a northeasterly oriented arc-normal component of motion in forearc velocities indicates that there are complexities involved beyond a simple interpretation of sliver motion being driven by oblique convergence. The forearc is reasonably well-fit by …


Observation Of Glacial Isostatic Adjustment In “Stable” North America With Gps, Giovanni F. Sella, Seth Stein, Timothy H. Dixon, Michael Craymer, Thomas S. James, Stephane Mazzotti, Roy K. Dokka Jan 2007

Observation Of Glacial Isostatic Adjustment In “Stable” North America With Gps, Giovanni F. Sella, Seth Stein, Timothy H. Dixon, Michael Craymer, Thomas S. James, Stephane Mazzotti, Roy K. Dokka

School of Geosciences Faculty and Staff Publications

Motions of three hundred and sixty Global Positioning System (GPS) sites in Canada and the United States yield a detailed image of the vertical and horizontal velocity fields within the nominally stable interior of the North American plate. By far the strongest signal is the effect of glacial isostatic adjustment (GIA) due to ice mass unloading during deglaciation. Vertical velocities show present-day uplift (∼10 mm/yr) near Hudson Bay, the site of thickest ice at the last glacial maximum. The uplift rates generally decrease with distance from Hudson Bay and change to subsidence (1–2 mm/yr) south of the Great Lakes. The …


Cenozoic Extensional Processes And Tectonics In The Northern Rocky Mountains: Southwest Montana And Eastern Idaho, Susanne U. Janecke Jan 2007

Cenozoic Extensional Processes And Tectonics In The Northern Rocky Mountains: Southwest Montana And Eastern Idaho, Susanne U. Janecke

Geosciences Faculty Publications

No abstract provided.


Pleistocene Brawley And Ocotillo Formations: Evidence For Initial Strike-Slip Deformation Along The San Felipe And San Jacinto Fault Zones, Southern California, S. M. Kirby, Susanne U. Janecke, R. J. Dorsey, B. A. Housen, K. Mcdougall, V. Langenheim, A. Steely Jan 2007

Pleistocene Brawley And Ocotillo Formations: Evidence For Initial Strike-Slip Deformation Along The San Felipe And San Jacinto Fault Zones, Southern California, S. M. Kirby, Susanne U. Janecke, R. J. Dorsey, B. A. Housen, K. Mcdougall, V. Langenheim, A. Steely

Geosciences Faculty Publications

We examine the Pleistocene tectonic reorganization of the Pacific–North American plate boundary in the Salton Trough of southern California with an integrated approach that includes basin analysis, magnetostratigraphy, and geologic mapping of upper Pliocene to Pleistocene sedimentary rocks in the San Felipe Hills. These deposits preserve the earliest sedimentary record of movement on the San Felipe and San Jacinto fault zones that replaced and deactivated the late Cenozoic West Salton detachment fault. Sandstone and mudstone of the Brawley Formation accumulated between ∼1.1 and ∼0.6–0.5 Ma in a delta on the margin of an arid Pleistocene lake, which received sediment from …


Integrated Geophysical Data Processing And Interpretation Of Crustal Structure In Ethiopia With Emphasis On The Ogaden Basin And Adjacent Areas, Ketsela Tadesse Jan 2007

Integrated Geophysical Data Processing And Interpretation Of Crustal Structure In Ethiopia With Emphasis On The Ogaden Basin And Adjacent Areas, Ketsela Tadesse

Open Access Theses & Dissertations

The combined effects of magmatism and stretching due to asthenosphere upwelling modifies the crustal structure of the Earth as seen in the Ethiopian rift and adjacent areas. The Ethiopian rift provides unique opportunities to understand the nature of rifted crust and the intensity of its modification by magmatic processes. I used geological and geophysical data to conduct an integrated study in and around the Ethiopian rift including the northern Kenyan rift and the northern part of the Kenyan dome. New gravity, controlled source seismic, and teleseismic data from the EAGLE (Ethiopia-Afar Geoscientific Lithospheric Experiment) were used as additional constraints in …


Biogeography And The Cambrian Radiation Of Arachnomorph Arthropods, Jonathan R. Hendricks, Bruce S. Lieberman Jan 2007

Biogeography And The Cambrian Radiation Of Arachnomorph Arthropods, Jonathan R. Hendricks, Bruce S. Lieberman

Faculty Publications

Biogeographic patterns in primarily Cambrian arachnomorph taxa are investigated using a recently constructed phylogenetic hypothesis in order to explore the biogeographic context of the Cambrian radiation. A modified version of Brooks Parsimony Analysis is employed to elucidate patterns of vicariance and geodispersal in taxa from six regions (Laurentia, Baltica, Siberia, Australia, Africa and China). Well resolved vicariance and geodispersal trees are very similar and reconstruct Laurentia and China as sister areas. This close area relationship between Laurentia and China provides extensive evidence for congruent vicariance and range expansion in Cambrian arachnomorphs, while data from trilobites do not show this pattern. …


Speleothems As Indicators Of Wet And Dry Periods, Ian John Fairchild, Emily Anne Mcmillan Jan 2007

Speleothems As Indicators Of Wet And Dry Periods, Ian John Fairchild, Emily Anne Mcmillan

International Journal of Speleology

Calcareous speleothems provide a record of dripwater composition which in turn is a function of climatic conditions. The historical focus of speleothem palaeoclimate studies has been on the derivation of palaeotemperatures through oxygen isotope studies. However, it is now realized that water availability is a more generally important control on their characteristics. Growth rate and growth morphology in principle should give rise to recognizable changes at low flow. However, accidental plumbing effects during aquifer evolution, can also lead to variations in water supply and it is not easy to distinguish these effects. In areas where there is a strong amount …


The Fate Of Nitrogren Fixed By Diazotrophs In The Ocean, Margaret R. Mulholland Jan 2007

The Fate Of Nitrogren Fixed By Diazotrophs In The Ocean, Margaret R. Mulholland

OES Faculty Publications

While we now know that N2 fixation is a significant source of new nitrogen (N) in the marine environment, little is known about the fate of this N (and associated C), despite the importance of diazotrophs to global carbon and nutrient cycles. Specifically, does N fixed during N2 fixation fuel autotrophic or heterotrophic growth and thus facilitate carbon (C) export from the euphotic zone, or does it contribute primarily to bacterial productivity and respiration in the euphotic zone? For Trichodesmium, the diazotroph we know the most about, the transfer of recently fixed N2 (and C) appears …


Gis-Based Integration Of Swat And Remm For Estimating Water Quality Benefits Of Riparian Buffers In Agricultural Watersheds, Y. Liu, Wanhong Yang, Xixi Wang Jan 2007

Gis-Based Integration Of Swat And Remm For Estimating Water Quality Benefits Of Riparian Buffers In Agricultural Watersheds, Y. Liu, Wanhong Yang, Xixi Wang

Civil & Environmental Engineering Faculty Publications

The Soil and Water Assessment Tool (SWAT) is a process-based, watershed-scale model with a hydrologic response unit (HRU) as the basic computation element, which makes it difficult to accurately represent riparian buffers using their physical parameters (e.g., vegetation structure). On the other hand, the field-scale Riparian Ecosystem Management Model (REMM) provides the opportunity to consider details of hydrologic processes within a riparian buffer zone. However, the runoff and its associated constituents from the upland area that is hydraulically connected to the riparian buffer zone must be provided as inputs into REMM. The rationale proposed here is that the integration of …


Co2 Control Of Trichodesmium N-2 Fixation, Photosynthesis, Growth Rates, And Elemental Ratios: Implications For Past, Present, And Future Ocean Biogeochemistry, D. A. Hutchins, F.-X. Fu, Y. Zhang, M. E. Warner, Y. Feng, K. Portune, P. W. Bernhardt, M. R. Mulholland Jan 2007

Co2 Control Of Trichodesmium N-2 Fixation, Photosynthesis, Growth Rates, And Elemental Ratios: Implications For Past, Present, And Future Ocean Biogeochemistry, D. A. Hutchins, F.-X. Fu, Y. Zhang, M. E. Warner, Y. Feng, K. Portune, P. W. Bernhardt, M. R. Mulholland

OES Faculty Publications

Diazotrophic marine cyanobacteria in the genus Trichodesmium contribute a large fraction of the new nitrogen entering the oligotrophic oceans, but little is known about how they respond to shifts in global change variables such as carbon dioxide (CO2) and temperature. We compared Trichodesmium dinitrogen (N2) and CO2 fixation rates during steady-state growth under past, current, and future CO2 scenarios, and at two relevant temperatures. At projected CO2 levels of year 2100 (76 Pa, 750 ppm), N2 fixation rates of Pacific and Atlantic isolates increased 35-100%, and CO2 fixation rates increased 15-128% …