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John M. Edmond - One of the best experts on this subject based on the ideXlab platform.
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controls over the strontium isotope composition of river water
Geochimica et Cosmochimica Acta, 1992Co-Authors: Martin R. Palmer, John M. EdmondAbstract:Abstract Strontium concentrations and isotope ratios have been measured in river and ground waters from the Ganges, Orinoco, and Amazon river basins. When compared with major element concentrations, the data set has allowed a detailed examination of the controls over the strontium isotope systematics of riverine input to the oceans in the following environments: 1. (1) “typical” drainage basins containing limestones, evaporites, shales, and alumino-silicate metamorphic and igneous rocks; 2. (2) shield terrains containing no chemical or biogenic sediments; and 3. (3) the floodplains that constitute the largest areas of many large rivers. The strontium concentration and isotope composition of river waters are largely defined by mixing of strontium derived from limestones and evaporites with strontium derived from silicate rocks. The strontium isotope composition of the limestone endmember generally lies within the Phanerozoic seawater range, which buffers the 87 Sr 86 Sr ratios of major rivers. A major exception is provided by the rivers draining the Himalayas, where widescale regional metamorphism appears to have led to an enrichment in limestones of radiogenic strontium derived from coexisting silicate rocks. The strontium isotope systematics of rivers draining shield areas are controlled by the intense, transportlimited, nature of the weathering reactions, and thereby limits variations in the strontium flux from these terrains. Floodplains are only a minor source of dissolved strontium to river waters, and precipitation of Soil Salts in some floodplains can reduce the riverine flux of dissolved strontium to the oceans. The most effective mechanisms for altering the isotope ratio and flux of riverine strontium to the oceans are increased glaciation and large-scale regional metamorphism of the type produced during continental collision. Both mechanisms provide a means for increasing the 87 Sr 86 Sr ratio of the global riverine flux.
Martin R. Palmer - One of the best experts on this subject based on the ideXlab platform.
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controls over the strontium isotope composition of river water
Geochimica et Cosmochimica Acta, 1992Co-Authors: Martin R. Palmer, John M. EdmondAbstract:Abstract Strontium concentrations and isotope ratios have been measured in river and ground waters from the Ganges, Orinoco, and Amazon river basins. When compared with major element concentrations, the data set has allowed a detailed examination of the controls over the strontium isotope systematics of riverine input to the oceans in the following environments: 1. (1) “typical” drainage basins containing limestones, evaporites, shales, and alumino-silicate metamorphic and igneous rocks; 2. (2) shield terrains containing no chemical or biogenic sediments; and 3. (3) the floodplains that constitute the largest areas of many large rivers. The strontium concentration and isotope composition of river waters are largely defined by mixing of strontium derived from limestones and evaporites with strontium derived from silicate rocks. The strontium isotope composition of the limestone endmember generally lies within the Phanerozoic seawater range, which buffers the 87 Sr 86 Sr ratios of major rivers. A major exception is provided by the rivers draining the Himalayas, where widescale regional metamorphism appears to have led to an enrichment in limestones of radiogenic strontium derived from coexisting silicate rocks. The strontium isotope systematics of rivers draining shield areas are controlled by the intense, transportlimited, nature of the weathering reactions, and thereby limits variations in the strontium flux from these terrains. Floodplains are only a minor source of dissolved strontium to river waters, and precipitation of Soil Salts in some floodplains can reduce the riverine flux of dissolved strontium to the oceans. The most effective mechanisms for altering the isotope ratio and flux of riverine strontium to the oceans are increased glaciation and large-scale regional metamorphism of the type produced during continental collision. Both mechanisms provide a means for increasing the 87 Sr 86 Sr ratio of the global riverine flux.
Rifat Akış - One of the best experts on this subject based on the ideXlab platform.
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Spatial variability of Soil solute and saturated hydraulic conductivity affected by undrained water table conditions
Precision Agriculture, 2015Co-Authors: Rifat AkışAbstract:Spatial information of Soil solute and saturated hydraulic conductivity under undrained water table conditions can provide explicit knowledge to better manage Soil and water than nonspatial management practices. This research was conducted to determine spatial structure of Soil saturated hydraulic conductivity and salt content, as influenced by undrained water table conditions in the Amik Plain of Turkey. Using grid sampling, the General Directorate of Turkish State Hydraulic Works sampled the Amik Plain Soils at approximately 1 600 locations, 254 of which were examined through undisturbed Soil core sampling for land drainage evaluation. Geostatistical analyses revealed that the 30–60 and 90–120 cm Soil layers had a shift in the particle size and were exposed to two different alluvial Soil forming processes. Mean Soil Ksat steadily decreased from 1.05 to 0.99 cm h^−1 and mean salt content increased from 0.307 to 0.335 % below the 30 to 60-cm layer. Correlation distance varied from 710 to 1 130 m for Soil Ksat and 1 000–1 130 m for Soil salt content for horizontal variograms. Nugget values of the models for Soil Ksat ranged from 0.031 to 0.036, while the range of nugget was from 0.002 to 0.18 for Soil salt content. Sill variance was the highest for Ksat (0.201) from 30 to 60 cm layer and Soil Salts (1.18) from 60 to 90 cm layer. Soil profile was moderately to heavily saline (1.69–7.73 dS m^−1). For the vertical variograms, correlation distance was approximately 75 cm for Soil Ksat and 136 cm for Soil salt content. Results showed that an 1 130 m × 1 130 m subfield with 75 cm and/or deeper depth could be used for the layout of drain tiles. Further studies of long-term spatial variability of these properties under drained and undrained conditions with anisotropy are needed for sound surface and subsurface drainage system implementations in the Amik Plain.
Huijie Xiao - One of the best experts on this subject based on the ideXlab platform.
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Soil salinity sodicity and cotton yield parameters under different drip irrigation regimes during saline wasteland reclamation
Agricultural Water Management, 2018Co-Authors: Ruoshui Wang, Huijie XiaoAbstract:Abstract A field trial consisting of cotton grown employing a combination of ridge planting, mulching with film, and drip irrigation was laid out on a plot with severely saline Soil in a typical inland arid area of Xinjiang. The effect of five levels of Soil matric potential set up 0.2 m below the drip emitter, namely −5 kPa, −10 kPa, −15 kPa, −20 kPa, and −25 kPa, were studied in terms of changes in Soil salinity (ECe), sodicity (SAR), crop growth and yield components. Drip irrigation increased the leaching of Soil Salts and decreased the ECe and SAR of each Soil layer. Although the levels of Soil salt rose again, in spring and winter, after irrigation was discontinued, the root zone (0–40 cm) remained less saline: the ECe and SAR value under the Soil matric potential of −5 kPa and −10 kPa were 63% and 49% of its values in 2009 respectively, before the land was brought under cultivation (p ≤ 0.05), showing maximum leaching. The yield of cotton peaked at the Soil matric potential of −5 kPa. The germination rate, which was the main factor that influenced the cotton yield, was 67% of that in non-saline Soil in the first two years, and increased to 84% in the third year. After three years, the rate of germination in all the treatments exceeded 67%, and the highest rate (78%) was at −5 kPa; in the same treatment, boll yield was 4.40 g per plant. Except for germination rate and the yield of lint and seed, all the yield components increased significantly (p ≤0.05) as ECe and SAR decreased in 2010 and 2011. The correlation between Soil salt (salinity and sodicity) and other components such as the number of cotton bolls per plant, the average weight of a boll, and lint percentage varied, probably because water supply was being regulated and, as a result, the physicochemical properties of the Soil kept changing constantly. Taking into account the extent of leaching, crop growth, and yield, the lower limit for the Soil matric potential should be −5 kPa at 20 cm below the dripper for the first three years during reclamation to promote cotton cultivation on the saline-sodic Soil of Xinjiang.
W. Berry Lyons - One of the best experts on this subject based on the ideXlab platform.
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Hypersaline “wet patches” in Taylor Valley, Antarctica
Geophysical Research Letters, 2012Co-Authors: Joseph S. Levy, Andrew G. Fountain, Kathy A. Welch, W. Berry LyonsAbstract:[1] Spatially isolated patches of Soil located in Taylor Valley, McMurdo Dry Valleys, Antarctica, are sites of elevated salt content and Soil moisture. During Antarctic spring, in the absence of snow melt, visibly wet (reduced albedo) patches of Soil are present at the surface. The Soil pore fluids are hypersaline and have average water activity of 0.74 (the water activity of a solution determines the equilibrium vapor pressure of that solution), and are an order of magnitude more saline than average Soils in the Dry Valleys. These salty Soils are 3–5 times more water rich than average Soils. Geochemical and meteorological analyses show that these wet patches are sites of direct vapor emplacement into Soil pore fluids that may ultimately be sourced by the deliquescence of Soil Salts. These wet patches represent a non-precipitation, non-groundwater source for water into Antarctic permafrost.
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Water tracks and permafrost in Taylor Valley, Antarctica: Extensive and shallow groundwater connectivity in a cold desert ecosystem
Geological Society of America Bulletin, 2011Co-Authors: Joseph S. Levy, Michael N. Gooseff, Andrew G. Fountain, Kathy A. Welch, W. Berry LyonsAbstract:Water tracks are zones of high Soil moisture that route water downslope over the ice table in polar environments. We present physical, hydrological, and geochemical evidence collected in Taylor Valley, McMurdo Dry Valleys, Antarctica, which suggests that previously unexplored water tracks are a significant component of this cold desert land system and constitute the major flow path in a cryptic hydrological system. Geological, geochemical, and hydrological analyses show that the water tracks are generated by a combination of infiltration from melting snowpacks, melting of pore ice at the ice table beneath the water tracks, and melting of buried segregation ice formed during winter freezing. The water tracks are enriched in solutes derived from chemical weathering of sediments as well as from dissolution of Soil Salts. The water tracks empty into ice-covered lakes, such as Lake Hoare, resulting in the interfingering of shallow groundwater solutions and glacier-derived stream water, adding complexity to the geochemical profile. Approximately four orders of magnitude less water is delivered to Lake Hoare by any given water track than is delivered by surface runoff from stream flow; however, the solute delivery to Lake Hoare by water tracks equals or may exceed the mass of solutes delivered from stream flow, making water tracks significant geochemical pathways. Additionally, solute transport is two orders of magnitude faster in water tracks than in adjacent dry or damp Soil, making water tracks “salt superhighways” in the Antarctic cold desert. Accordingly, water tracks represent a new geological pathway that distributes water, energy, and nutrients in Antarctic Dry Valley, cold desert, Soil ecosystems, providing hydrological and geochemical connectivity at the hillslope scale.
