|   | 
Details
   web
Records
Author Chase, B.M.; Meadows, M.E.
Title Late Quaternary dynamics of southern Africa’s winter rainfall zone Type Journal Article
Year (down) 2007 Publication Earth-Science Reviews Abbreviated Journal
Volume 84 Issue 3 Pages 103-138
Keywords Last Glacial Maximum, palaeoenvironment, Quaternary, southern Africa, westerlies, winter rainfall zone
Abstract Variations in the nature and extent of southern Africa’s winter rainfall zone (WRZ) have the potential to provide important information concerning the nature of long-term climate change at both regional and hemispheric scales. Positioned at the interface between tropical and temperate systems, southern Africa’s climate is influenced by shifts in the Intertropical Convergence Zone, the westerlies, and the development and position of continental and oceanic anticyclones. Over the last glacial–interglacial cycle substantial changes in the amount and seasonality of precipitation across the subcontinent have been linked to the relative dominance of these systems. Central to this discussion has been the extent to which the region’s glacial climates would have been affected by expansions of Antarctic sea-ice, equatorward migrations of the westerlies, more frequent/intense winter storms and an expanded WRZ. This paper reviews the developing body of evidence pertaining to shifts in the WRZ, and the evolution of ideas that have been presented to explain the patterns observed. Dividing the region into three separate axes, along the western and southern margins of the continent and across the interior into the Karoo and the Kalahari, a range of evidence from both terrestrial sites and marine cores is considered, and potential expansions of the WRZ expansions are explored. Despite the limitations of many of the region’s proxy records, a coherent pattern has begun to develop of a significantly expanded WRZ during phases of the last glacial period, with the best-documented being between 32–17 ka. While more detailed inferences will require the recovery and analysis of longer and better-dated records, this synthesis provides a new baseline for further research in this key region.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0012-8252 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number THL @ christoph.kuells @ chase_late_2007 Serial 102
Permanent link to this record
 

 
Author Yabusaki, S.B.; Fang, Y.; Long, P.E.; Resch, C.T.; Peacock, A.D.; Komlos, J.; Jaffe, P.R.; Morrison, S.J.; Dayvault, R.D.; White, D.C.; Anderson, R.T.
Title Uranium removal from groundwater via in situ biostimulation: Field-scale modeling of transport and biological processes Type Journal Article
Year (down) 2007 Publication Journal of Contaminant Hydrology Abbreviated Journal
Volume 93 Issue 1 Pages 216-235
Keywords Bioremediation, Biostimulation, Field experiment, Iron, Reactive transport, Sulfate, Uranium
Abstract During 2002 and 2003, bioremediation experiments in the unconfined aquifer of the Old Rifle UMTRA field site in western Colorado provided evidence for the immobilization of hexavalent uranium in groundwater by iron-reducing Geobacter sp. stimulated by acetate amendment. As the bioavailable Fe(III) terminal electron acceptor was depleted in the zone just downgradient of the acetate injection gallery, sulfate-reducing organisms came to dominate the microbial community. In the present study, we use multicomponent reactive transport modeling to analyze data from the 2002 field experiment to identify the dominant transport and biological processes controlling uranium mobility during biostimulation, and determine field-scale parameters for these modeled processes. The coupled process simulation approach was able to establish a quantitative characterization of the principal flow, transport, and reaction processes based on the 2002 field experiment, that could be applied without modification to describe the 2003 field experiment. Insights gained from this analysis include field-scale estimates of the bioavailable Fe(III) mineral threshold for the onset of sulfate reduction, and rates for the Fe(III), U(VI), and sulfate terminal electron accepting processes.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0169-7722 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number THL @ christoph.kuells @ yabusaki_uranium_2007 Serial 156
Permanent link to this record
 

 
Author Strandmann, P.A.E.P. von; Reynolds, B.C.; Porcelli, D.; James, R.H.; Calsteren, P. van; Baskaran, M.; Burton, K.W.
Title Assessing continental weathering rates and actinide transport in the Great Artesian Basin Type Journal Article
Year (down) 2006 Publication Geochimica et Cosmochimica Acta Abbreviated Journal
Volume 70 Issue 18, Supplement Pages 497
Keywords
Abstract
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0016-7037 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number THL @ christoph.kuells @ strandmann_assessing_2006 Serial 116
Permanent link to this record
 

 
Author Frumkin, A.; Gvirtzman, H.
Title Cross-formational rising groundwater at an artesian karstic basin: the Ayalon Saline Anomaly, Israel Type Journal Article
Year (down) 2006 Publication Journal of Hydrology Abbreviated Journal
Volume 318 Issue 1 Pages 316-333
Keywords Confined karst, Groundwater, HS, Maze caves, Rising water, Yarkon–Taninim aquifer
Abstract It is proposed that a geothermal artesian karstic system at the central part of the Yarkon–Taninim aquifer creates the ‘Ayalon Saline Anomaly’ (ASA), whose mechanism has been under debate for several decades. A 4-year-long detailed groundwater monitoring was carried out at 68 new shallow boreholes in the Ayalon region, accompanied by a comprehensive survey of karstic voids. Results indicate the rising of warm-brackish groundwater through highly permeable swarms of karstic shafts, serving as an outflow of the artesian geothermal system. The ASA area contains ‘hot spots’, where groundwater contrasts with ‘normal’ water hundreds of meters away. The ASA temperature reaches 30°C (∼5°C warmer than its surroundings), chloride concentration reaches 528mg/l (50–100mg/l in the surrounding), H2S concentration reaches 5.6mg/l (zero all around) and pH value is 7.0 (compared with 7.8 around). Subsequently, the hydrothermal water flows laterally of at the watertable horizon through horizontal conduits, mixing with ‘normal’ fresh water which had circulated at shallow depth. Following rainy seasons, maximal watertable rise is observed in the ASA compared to its surroundings. Regional hydrogeology considerations suggest that the replenishment area for the ASA water is at the Samaria Mountains, east of the ASA. The water circulates to a great depth while flowing westward, and a cross-formational upward flow is then favored close the upper sub-aquifer’s confinement border.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0022-1694 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number THL @ christoph.kuells @ frumkin_cross-formational_2006 Serial 117
Permanent link to this record
 

 
Author Gómez, P.; Garralón, A.; Buil, B.; Turrero, M.J.; Sánchez, L.; Cruz, B. de la
Title Modeling of geochemical processes related to uranium mobilization in the groundwater of a uranium mine Type Journal Article
Year (down) 2006 Publication Science of The Total Environment Abbreviated Journal
Volume 366 Issue 1 Pages 295-309
Keywords Geochemical modeling, Granite, Groundwater, Uranium mine, Uranium retention
Abstract This paper describes the processes leading to uranium distribution in the groundwater of five boreholes near a restored uranium mine (dug in granite), and the environmental impact of restoration work in the discharge area. The groundwater uranium content varied from \textless1 μg/L in reduced water far from the area of influence of the uranium ore-containing dyke, to 104 μg/L in a borehole hydraulically connected to the mine. These values, however, fail to reflect a chemical equilibrium between the water and the pure mineral phases. A model for the mobilization of uranium in this groundwater is therefore proposed. This involves the percolation of oxidized waters through the fractured granite, leading to the oxidation of pyrite and arsenopyrite and the precipitation of iron oxyhydroxides. This in turn leads to the dissolution of the primary pitchblende and, subsequently, the release of U(VI) species to the groundwater. These U(VI) species are retained by iron hydroxides. Secondary uranium species are eventually formed as reducing conditions are re-established due to water–rock interactions.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0048-9697 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number THL @ christoph.kuells @ gomez_modeling_2006 Serial 162
Permanent link to this record
 

 
Author Min, M.; Chen, J.; Wang, J.; Wei, G.; Fayek, M.
Title Mineral paragenesis and textures associated with sandstone-hosted roll-front uranium deposits, NW China Type Journal Article
Year (down) 2005 Publication Ore Geology Reviews Abbreviated Journal
Volume 26 Issue 1 Pages 51-69
Keywords China, Mineralogy, Paragenesis, Sandstone-hosted roll-type uranium deposit
Abstract We present a first paragenetic study of the Wuyier, Wuyisan, Wuyiyi and Shihongtan sandstone-hosted roll-front uranium deposits, northwest China. The mineralization is hosted by Lower–Middle Jurassic coarse- to medium-grained sandstones, which are dark-gray to black due to a mixture of ore minerals and carbonaceous debris. The sandstone is alluvial fan-braided river facies. Minerals associated with these deposits can be broadly categorized as detrital, authigenic, and ore-stage mineralization. Ore minerals consist of uraninite and coffinite. This is the first noted occurrence of coffinite in this type of deposit in China. Sulfide minerals associated with the uranium minerals are pyrite, marcasite, and less commonly, sphalerite and galena. The sulfide minerals are largely in textural equilibrium with the uranium minerals. However, these sulfide minerals occasionally appear to predate, as well as postdate, the uranium minerals. This implies that there are multiple generations of sulfides associated with these deposits. The ore minerals occur interstitially between fossilized wood cells in the sandstones as well as replace fossilized wood and biotite. The deposits are generally low-grade. Primary uranium minerals associated with the low-grade deposits are generally too small, ranging from 0.2 to 0.3 μm in diameter, to be observed by optical microscopy and are only observed by electron microscopy. Mineral paragenesis and textures indicate that these deposits formed under low temperature (30–50 °C) conditions.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0169-1368 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number THL @ christoph.kuells @ min_mineral_2005 Serial 175
Permanent link to this record
 

 
Author Min, M.; Xu, H.; Chen, J.; Fayek, M.
Title Evidence of uranium biomineralization in sandstone-hosted roll-front uranium deposits, northwestern China Type Journal Article
Year (down) 2005 Publication Ore Geology Reviews Abbreviated Journal
Volume 26 Issue 3 Pages 198-206
Keywords Biomineralization, China, Roll-front uranium deposit, Sandstone
Abstract We show evidence that the primary uranium minerals, uraninite and coffinite, from high-grade ore samples (U3O8\textgreater0.3%) in the Wuyiyi, Wuyier, and Wuyisan sandstone-hosted roll-front uranium deposits, Xinjiang, northwestern China were biogenically precipitated and psuedomorphically replace fungi and bacteria. Uranium (VI), which was the sole electron acceptor, was likely to have been enzymically reduced. Post-mortem accumulation of uranium may have also occurred through physio-chemical interaction between uranium and negatively-charged cellular sites, and inorganic adsorption or precipitation reactions. These results suggest that microorganisms may have played a key role in formation of the sandstone- or roll-type uranium deposits, which are among the most economically significant uranium deposits in the world.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0169-1368 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number THL @ christoph.kuells @ min_evidence_2005 Serial 186
Permanent link to this record
 

 
Author Schwiede, M.; Duijnisveld, W.H.M.; Böttcher, J.
Title Investigation of processes leading to nitrate enrichment in soils in the Kalahari Region, Botswana Type Journal Article
Year (down) 2005 Publication Physics and Chemistry of the Earth, Parts A/B/C Abbreviated Journal
Volume 30 Issue 11 Pages 712-716
Keywords Nitrate, Arenosol soils, Semi-arid, Kalahari, Cattle, Chloride, Travel time
Abstract In Southern Africa elevated nitrate concentrations are observed in mostly uninhabited semi-arid areas. In the Kalahari of Botswana groundwater locally exhibits concentrations up to 600mg/l. It is assumed, that nitrate found in the groundwater originates mainly from nitrogen input and transformations in the soils. Our investigations in the Kalahari between Serowe and Orapa show that cattle raising is an important source for enhanced nitrate concentrations in the soils (Arenosols). But also in termite mounds very high nitrate stocks were found, and under natural vegetation (acacia trees and shrubs) nitrate concentrations were mostly unexpectedly high. This nitrate enrichment in the soils poses a serious threat to the groundwater quality. However, calculated soil water age distributions in the unsaturated zone clearly show that today’s nitrate pollution of the groundwater below the investigation area could originate from natural sources, but cannot be caused by the current land use for cattle raising.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1474-7065 ISBN Medium
Area Expedition Conference
Notes Integrated Water Resources Management (IWRM) and the Millennium Development Goals: Managing Water for Peace and Prosperity Approved no
Call Number THL @ christoph.kuells @ Schwiede2005712 Serial 276
Permanent link to this record
 

 
Author Orloff, K.G.; Mistry, K.; Charp, P.; Metcalf, S.; Marino, R.; Shelly, T.; Melaro, E.; Donohoe, A.M.; Jones, R.L.
Title Human exposure to uranium in groundwater Type Journal Article
Year (down) 2004 Publication Environmental Research Abbreviated Journal
Volume 94 Issue 3 Pages 319-326
Keywords Groundwater, Human exposure, Uranium, Urine
Abstract High concentrations of uranium (mean=620μg/L) were detected in water samples collected from private wells in a residential community. Based on isotopic analyses, the source of the uranium contamination appeared to be from naturally occurring geological deposits. In homes where well water concentrations of uranium exceeded the drinking water standard, the residents were advised to use an alternate water source for potable purposes. Several months after the residents had stopped drinking the water, urine samples were collected and tested for uranium. Elevated concentrations of uranium (mean=0.40μg/g creatinine) were detected in urine samples, and 85 percent of the urine uranium concentrations exceeded the 95th percentile concentration of a national reference population. Urine uranium concentrations were positively correlated with water uranium concentrations, but not with the participants’ ages or how long they had been drinking the water. Six months later, a second urine sample was collected and tested for uranium. Urine uranium concentrations decreased in most (63 percent) of the people. In those people with the highest initial urine uranium concentrations, the urine levels decreased an average of 78 percent. However, urine uranium concentrations remained elevated (mean=0.27μg/g), and 87 percent of the urine uranium concentrations exceeded the 95th percentile concentration of the reference population. The results of this investigation demonstrated that after long-term ingestion of uranium in drinking water, elevated concentrations of uranium in urine could be detected up to 10 months after exposure had stopped.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0013-9351 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number THL @ christoph.kuells @ orloff_human_2004 Serial 136
Permanent link to this record
 

 
Author Edmunds, W.M.; Shand, P.; Hart, P.; Ward, R.S.
Title The natural (baseline) quality of groundwater: a UK pilot study Type Journal Article
Year (down) 2003 Publication Science of The Total Environment Abbreviated Journal
Volume 310 Issue 1 Pages 25-35
Keywords Baseline quality, Groundwater, Hydrogeochemistry, Monitoring, Water Policy
Abstract Knowledge of the natural baseline quality of groundwaters is an essential prerequisite for understanding pollution and for imposing regulatory limits. The natural baseline of groundwaters may show a range of concentrations depending on aquifer mineralogy, facies changes, flow paths and residence time. The geochemical controls on natural concentrations are discussed and an approach to defining baseline concentrations using geochemical and statistical tools is proposed. The approach is illustrated using a flowline from the Chalk aquifer in Berkshire, UK where aerobic and anaerobic sections of the aquifer are separately considered. The baseline concentrations for some elements are close to atmospheric values whereas others evolve through time-dependent water–rock interaction. Certain solutes (K, NH4+), often considered contaminants, reach naturally high concentrations due to geochemical controls; transition metal concentrations are generally low, although their concentrations may be modified by redox controls. It is recommended that the baseline approach be incorporated into future management strategies, notably monitoring.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0048-9697 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number THL @ christoph.kuells @ edmunds_natural_2003 Serial 166
Permanent link to this record