Littérature scientifique sur le sujet « Rock weathering, Dissolved oxygen »
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Articles de revues sur le sujet "Rock weathering, Dissolved oxygen":
1
Chigira, Masahiro. « Dissolution and oxidation of mudstone under stress ». Canadian Geotechnical Journal 30, no 1 (1 février 1993) : 60–70. http://dx.doi.org/10.1139/t93-006.
Résumé :
Weathering of soft mudstone in nature, characterized by the presence of an oxidized zone and an underlying dissolved zone, was simulated in the laboratory in 15 °C water with a pH of 3–7 and dissolved oxygen contents of 4–16 mg/L under stresses up to 0.49 MPa for as long as 70 days. When the water is acid, hydrogen ions diffuse from the rock–water interface through the rock and attack acid-labile calcite in mudstone preferentially and easily at a well-defined dissolution front, leaving a dissolved zone behind the front. Density decreases, porosity increases, ultrasonic P-wave velocity decreases, and shear strength decreases in the dissolved zone. The dissolution front migrates toward unreacted rock, and the migration rate is controlled by the diffusion of hydrogen ions in the reacted dissolved zone, so the rate is influenced by the stress exerted on the rocks; the effective diffusivity becomes smaller when the rock is stressed. Oxygen also diffuses through the rock to a well-defined oxidation front and changes the rock color from greenish grey to pale brown by oxidation. Slight deterioration occurs with the color change and change in density, P-wave velocity, and porosity. Depletion of pyrite by oxidation and the complete color change take a long time in comparison with the slight color change. Chlorite seems to transform into smectite in acid and highly oxidizing conditions. Key words : mudstone, dissolution, oxidation, weathering.
2
Burt, Emily I., Markus Bill, Mark E. Conrad, Adan Julian Ccahuana Quispe, John N. Christensen, Robert G. Hilton, Mathieu Dellinger et A. Joshua West. « Conservative transport of dissolved sulfate across the Rio Madre de Dios floodplain in Peru ». Geology 49, no 9 (19 mai 2021) : 1064–68. http://dx.doi.org/10.1130/g48997.1.
Résumé :
Abstract Mineral weathering plays a primary role in the geologic carbon cycle. Silicate weathering by carbonic acid consumes CO2 and stabilizes Earth's climate system. However, when sulfuric acid drives weathering, CO2 can be released to the atmosphere. Recent work has established that sulfuric acid weathering resulting from sulfide mineral oxidation is globally significant and particularly important in rapidly eroding environments. In contrast, if SO42− produced by sulfide oxidation is reduced during continental transit, then CO2 release may be negated. Yet, little is known about how much SO42− reduction takes place in terrestrial environments. We report oxygen and sulfur stable isotope ratios of SO42− in river waters and mass budget calculations, which together suggest that SO42− released from pyrite oxidation in the Peruvian Andes mountains is conservatively exported across ∼300 km of the Amazon floodplain. In this system, floodplain SO42− reduction does not counteract the large SO42− flux from Andean pyrite weathering or measurably affect the stable isotope composition of riverine SO42−. These findings support the hypothesis that uplift and erosion of sedimentary rocks drive release of CO2 from the rock reservoir to the atmosphere.
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Roylands, Tobias, Robert G. Hilton, Erin L. McClymont, Mark H. Garnett, Guillaume Soulet, Sébastien Klotz, Mathis Degler, Felipe Napoleoni et Caroline Le Bouteiller. « Probing the exchange of CO2 and O2 in the shallow critical zone during weathering of marl and black shale ». Earth Surface Dynamics 12, no 1 (31 janvier 2024) : 271–99. http://dx.doi.org/10.5194/esurf-12-271-2024.
Résumé :
Abstract. Chemical weathering of sedimentary rocks can release carbon dioxide (CO2) and consume oxygen (O2) via the oxidation of petrogenic organic carbon and sulfide minerals. These pathways govern Earth's surface system and climate over geological timescales, but the present-day weathering fluxes and their environmental controls are only partly constrained due to a lack of in situ measurements. Here, we investigate the gaseous exchange of CO2 and O2 during the oxidative weathering of black shales and marls exposed in the French southern Alps. On six field trips over 1 year, we use drilled headspace chambers to measure the CO2 concentrations in the shallow critical zone and quantify CO2 fluxes in real time. Importantly, we develop a new approach to estimate the volume of rock that contributes CO2 to a chamber, and assess effective diffusive gas exchange, by first quantifying the mass of CO2 that is stored in a chamber and connected rock pores. Both rock types are characterized by similar contributing rock volumes and diffusive movement of CO2. However, CO2 emissions differed between the rock types, with yields over rock outcrop surfaces (inferred from the contributing rock volume and the local weathering depths) ranging on average between 73 and 1108 tCkm-2yr-1 for black shales and between 43 and 873 tCkm-2yr-1 for marls over the study period. Having quantified diffusive processes, chamber-based O2 concentration measurements are used to calculate O2 fluxes. The rate of O2 consumption increased with production of CO2, and with increased temperature, with an average O2:CO2 molar ratio of 10:1. If O2 consumption occurs by both rock organic carbon oxidation and carbonate dissolution coupled to sulfide oxidation, either an additional O2 sink needs to be identified or significant export of dissolved inorganic carbon occurs from the weathering zone. Together, our findings refine the tools we have to probe CO2 and O2 exchange in rocks at Earth's surface and shed new light on CO2 and O2 fluxes, their drivers, and the fate of rock-derived carbon.
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Shaffer, G., S. Malskǽr Olsen et J. O. P. Pedersen. « Presentation, calibration and validation of the low-order, DCESS Earth System Model ». Geoscientific Model Development Discussions 1, no 1 (23 juin 2008) : 39–124. http://dx.doi.org/10.5194/gmdd-1-39-2008.
Résumé :
Abstract. A new, low-order Earth system model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years. The atmosphere module considers radiation balance, meridional transport of heat and water vapor between low-mid latitude and high latitude zones, heat and gas exchange with the ocean and sea ice and snow cover. Gases considered are carbon dioxide and methane for all three carbon isotopes, nitrous oxide and oxygen. The ocean module has 100 m vertical resolution, carbonate chemistry and prescribed circulation and mixing. Ocean biogeochemical tracers are phosphate, dissolved oxygen, dissolved inorganic carbon for all three carbon isotopes and alkalinity. Biogenic production of particulate organic matter in the ocean surface layer depends on phosphate availability but with lower efficiency in the high latitude zone, as determined by model fit to ocean data. The calcite to organic carbon rain ratio depends on surface layer temperature. The semi-analytical, ocean sediment module considers calcium carbonate dissolution and oxic and anoxic organic matter remineralisation. The sediment is composed of calcite, non-calcite mineral and reactive organic matter. Sediment porosity profiles are related to sediment composition and a bioturbated layer of 0.1 m thickness is assumed. A sediment segment is ascribed to each ocean layer and segment area stems from observed ocean depth distributions. Sediment burial is calculated from sedimentation velocities at the base of the bioturbated layer. Bioturbation rates and oxic and anoxic remineralisation rates depend on organic carbon rain rates and dissolved oxygen concentrations. The land biosphere module considers leaves, wood, litter and soil. Net primary production depends on atmospheric carbon dioxide concentration and remineralization rates in the litter and soil are related to mean atmospheric temperatures. Methane production is a small fraction of the soil remineralization. The lithosphere module considers outgassing, weathering of carbonate and silicate rocks and weathering of rocks containing old organic carbon and phosphorus. Weathering rates are related to mean atmospheric temperatures. A pre-industrial, steady state calibration to Earth system data is carried out. Ocean observations of temperature, carbon 14, phosphate, dissolved oxygen, dissolved inorganic carbon and alkalinity constrain air-sea exchange and ocean circulation, mixing and biogeochemical parameters. Observed calcite and organic carbon distributions and inventories in the ocean sediment help constrain sediment module parameters. Carbon isotopic data and carbonate vs silicate weathering fractions are used to estimate initial lithosphere outgassing and rock weathering rates. Model performance is tested by simulating atmospheric greenhouse gas increases, global warming and model tracer evolution for the period 1765 to 2000, as forced by prescribed anthropogenic greenhouse gas inputs and other anthropogenic and natural forcing. Long term, transient model behavior is studied with a set of 100 000 year simulations, forced by a slow, 5000 GtC input of CO2 to the atmosphere, and with a 1.5 million year simulation, forced by a doubling of lithosphere CO2 outgassing.
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Shaffer, G., S. Malskær Olsen et J. O. Pepke Pedersen. « Presentation, calibration and validation of the low-order, DCESS Earth System Model (Version 1) ». Geoscientific Model Development 1, no 1 (6 novembre 2008) : 17–51. http://dx.doi.org/10.5194/gmd-1-17-2008.
Résumé :
Abstract. A new, low-order Earth System Model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years. The atmosphere module considers radiation balance, meridional transport of heat and water vapor between low-mid latitude and high latitude zones, heat and gas exchange with the ocean and sea ice and snow cover. Gases considered are carbon dioxide and methane for all three carbon isotopes, nitrous oxide and oxygen. The ocean module has 100 m vertical resolution, carbonate chemistry and prescribed circulation and mixing. Ocean biogeochemical tracers are phosphate, dissolved oxygen, dissolved inorganic carbon for all three carbon isotopes and alkalinity. Biogenic production of particulate organic matter in the ocean surface layer depends on phosphate availability but with lower efficiency in the high latitude zone, as determined by model fit to ocean data. The calcite to organic carbon rain ratio depends on surface layer temperature. The semi-analytical, ocean sediment module considers calcium carbonate dissolution and oxic and anoxic organic matter remineralisation. The sediment is composed of calcite, non-calcite mineral and reactive organic matter. Sediment porosity profiles are related to sediment composition and a bioturbated layer of 0.1 m thickness is assumed. A sediment segment is ascribed to each ocean layer and segment area stems from observed ocean depth distributions. Sediment burial is calculated from sedimentation velocities at the base of the bioturbated layer. Bioturbation rates and oxic and anoxic remineralisation rates depend on organic carbon rain rates and dissolved oxygen concentrations. The land biosphere module considers leaves, wood, litter and soil. Net primary production depends on atmospheric carbon dioxide concentration and remineralization rates in the litter and soil are related to mean atmospheric temperatures. Methane production is a small fraction of the soil remineralization. The lithosphere module considers outgassing, weathering of carbonate and silicate rocks and weathering of rocks containing old organic carbon and phosphorus. Weathering rates are related to mean atmospheric temperatures. A pre-industrial, steady state calibration to Earth system data is carried out. Ocean observations of temperature, carbon 14, phosphate, dissolved oxygen, dissolved inorganic carbon and alkalinity constrain air-sea exchange and ocean circulation, mixing and biogeochemical parameters. Observed calcite and organic carbon distributions and inventories in the ocean sediment help constrain sediment module parameters. Carbon isotopic data and carbonate vs. silicate weathering fractions are used to estimate initial lithosphere outgassing and rock weathering rates. Model performance is tested by simulating atmospheric greenhouse gas increases, global warming and model tracer evolution for the period 1765 to 2000, as forced by prescribed anthropogenic greenhouse gas inputs and other anthropogenic and natural forcing. Long term, transient model behavior is studied with a set of 100 000 year simulations, forced by a slow, 5000 Gt C input of CO2 to the atmosphere, and with a 1.5 million year simulation, forced by a doubling of lithosphere CO2 outgassing.
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Marchina, Chiara, Kay Knöller, Maddalena Pennisi, Claudio Natali, Marlene Dordoni, Paolo Di Giuseppe, Rosa Cidu et Gianluca Bianchini. « The Isotopic (δ18O, δ 2H, δ13C, δ15N, δ34S, 87Sr/86Sr, δ11B) Composition of Adige River Water Records Natural and Anthropogenic Processes ». Minerals 10, no 5 (18 mai 2020) : 455. http://dx.doi.org/10.3390/min10050455.
Résumé :
The water composition of the river Adige displays a Ca–HCO3 hydrochemical facies, mainly due to rock weathering. Nitrate is the only component that has increased in relation to growing anthropogenic inputs. The aim of this paper was to identify the origin of the dissolved components in this river and to establish the relationship between these components and critical zone processes within an evolving framework where climatic and human impacts are influencing the riverine system. In particular, emphasis is given to a wide spectrum of isotope data (δ18O, δ2H, δ13C, δ15N, δ34S, 87Sr/86Sr, δ11B), which is considered useful for determining water origin as well as natural and anthropogenic impacts on riverine geochemistry. Together with oxygen and hydrogen isotopes, which are strictly related to the climatic conditions (precipitation, temperature, humidity), the carbon, sulphur, strontium and boron signatures can describe the magnitude of rock weathering, which is in turn linked to the climatic parameters. δ13CDIC varies regularly along the riverine profile between −4.5‰ and −9.5‰, and δ34SSO4 varies regularly between +4.4‰ and +11.4‰. On the other hand, δ15NNO3 shows a more scattered distribution between +3.9‰ and +10.5‰, with sharp variations along the riverine profile. 87Sr/86Sr varies between 0.72797 in the upper part of the catchment and 0.71068 in the lower part. δ11B also shows a rough trend, with values approaching 7.6‰ in the upper part and 8.5‰ in the lower part. In our view, the comparatively low δ34S, δ11B, and high 87Sr/86Sr values, could be a proxy for increasing silicate weathering, which is a process that is sensitive to increases in temperature.
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Raj Pant, Ramesh, Khadka Bahadur Pal, Kiran Bishwakarma, Lal B Thapa, Alina Dangol, Binod Dawadi, Pramod Poudel, Binod Bhattarai, Tarka Raj Joshi et Youb Raj Bhatt. « Application of Multivariate Approaches to the Hydro-chemical Assessment of the Ghodaghodi Lake, Sudurpaschim Province, Nepal ». Nepal Journal of Science and Technology 19, no 2 (10 octobre 2021) : 46–54. http://dx.doi.org/10.3126/njst.v20i1.39390.
Résumé :
Wetlands are considered the most diverse and productive ecosystems in the world, providing life-sustaining ecological services. Hydrochemical variables of the Ghodaghodi Lake situated in Far west Nepal were studied using multivariate statistical approaches to investigate the characteristics of water quality of the lake. A total of 10water samples were collected and analyzed for water temperature, pH, electrical conductivity, total dissolved solids, total hardness, salinity, dissolved oxygen, major ions, and dissolved Si in the pre-monsoon season during 2017.The water quality assessment was carried out by applying sodium percentage, sodium adsorption ratio, permeability index, Kelly’s ratio, magnesium adsorption ratio, action ratio of soil structural stability, and water quality index. Multivariate statistical techniques were used to evaluate the geochemical and anthropogenic processes and to identify factors influencing the ionic concentrations. The results revealed that the water was slightly alkaline with low ionic strength and remarkable spatial variations. The hydrochemistry of the lake was mainly controlled by rock weathering as the dominant Ca2+-HCO3- facies. The principal component analysis provided three major components exhibiting the diverse sources of natural and anthropogenic chemicals, including agricultural fertilizers, leakage of sewages near the human settlements, etc. The measured hydrochemical parameters indicate that lake water lies within the safe drinking water and irrigational standards. However, special consideration should be taken to control the concentrations of NO3- due to increasing anthropic activities.
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SLEEP, NORMAN H., DENNIS K. BIRD et MINIK T. ROSING. « BIOLOGICAL EFFECTS ON THE SOURCE OF GEONEUTRINOS ». International Journal of Modern Physics A 28, no 30 (4 décembre 2013) : 1330047. http://dx.doi.org/10.1142/s0217751x13300470.
Résumé :
Detection of antineutrinos from U and Th series decay within the Earth (geoneutrinos) constrains the absolute abundance of these elements. Marine detectors will measure the ratio over the mantle beneath the site and provide spatial averaging. The measured mantle Th/U may well be significantly below its bulk earth value of ~4; Pb isotope measurements on mantle-derived rocks yield low Th/U values, effectively averaged over geological time. The physics of the modern biological process is complicated, but the net effect is that much of the U in the mantle comes from subducted marine sediments and subducted upper oceanic crust. That is, U subducts preferentially relative to Th. Oxygen ultimately from photosynthesis oxidizes U(IV) to U(VI), which is soluble during weathering and sediment transport. Dissolved U(VI) reacts with FeO in the oceanic crust and organic carbon within sediments to become immobile U(IV). These deep marine rocks are preferentially subducted relative to Th(IV)-bearing continental margin rocks. Ferric iron from anoxygenic photosynthesis and oxygen in local oases likely mobilized some U during the Archean Era when there was very little O2in the air. Conversely, these elements behave similarly in the absence of life, where the elements occur as U(IV) and Th(IV), which do not significantly fractionate during igneous processes. Neither do they fractionate during weathering, as they are essentially insoluble in water in surface environments. Th(IV) and U(IV) remain in solid clay-sized material. Overall, geoneutrino data constrain the masses of mantle chemical and isotopic domains recognized by studies of mantle-derived rocks and show the extent of recycling into the mantle over geological time.
9
Yang, Haijiao, Jiahua Wei et Kaifang Shi. « Hydrochemical and Isotopic Characteristics and the Spatiotemporal Differences of Surface Water and Groundwater in the Qaidam Basin, China ». Water 16, no 1 (31 décembre 2023) : 169. http://dx.doi.org/10.3390/w16010169.
Résumé :
In the context of climate change, precipitation and runoff in the arid inland basins of northwest China have undergone significant changes. The Qaidam Basin (QB) is a typical highland arid inland area. Understanding the spatial and temporal variations in surface water and groundwater chemistry and isotopes, as well as their causes, is crucial for future water resource management and ecological protection. Samples of river, lake, and groundwater, as well as others, were collected and tested in five typical watersheds in the summer and winter. The hydrochemistry and isotopic spatiotemporal differences in various water bodies were studied using the significant difference method, water vapor flux models, hydrochemistry, isotopes, and other methods for cause analyses. The results indicate the following: (1) There are differences in hydrochemistry between the southern and northern basins because the southern basin is more influenced by the dissolution of salt rocks and evaporation, whereas the northern basin is mainly affected by carbonate weathering. (2) The enrichment of δD and δ18O in the northern basin gradually increases from west to east, while in the southern basin, it is the opposite. This is because the southern basin receives a larger contribution of water vapor from the mid-latitude westerlies, while the northern basin primarily relies on local evaporation as its water vapor source. (3) Significant differences are observed in the total dissolved solids (TDS) and hydrochemical types of river water and groundwater between the summer and winter due to higher rates of rock weathering and evaporation in the summer. (4) The more pronounced seasonal differences in hydrogen and oxygen stable isotopes in the southern basin are due to higher rates of internal water vapor circulation in the summer. (5) The similarity in characteristics between river water and groundwater is the result of strong exchanges between river water and groundwater from piedmonts to terminals. The spatiotemporal heterogeneity of terminal lakes is attributed to the accumulation of salts and groundwater replenishment from other sources.
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Skoulikidis, Nikolaos T., Anastasia Lampou et Sofia Laschou. « Unraveling Aquatic Quality Controls of a Nearly Undisturbed Mediterranean Island (Samothraki, Greece) ». Water 12, no 2 (10 février 2020) : 473. http://dx.doi.org/10.3390/w12020473.
Résumé :
Due to its rough, mountainous relief, Samothraki remains one of the last minimally disturbed islands in the Mediterranean. This paper examines the hydrogeochemical regime of the island’s surface waters as it results from geological, morphological, and hydro(geo)logical controls within a frame of minimally disturbed environmental conditions. Shallow, fractured groundwater aquifers, in combination with steep slopes and predominant weathering resistant rocks, bring about flashy stream regimes with remarkably low solute concentrations. Streams and springs revealed hydrochemical similarities. Contrary to streams chiefly draining sedimentary rocks, streams underlined by granite and ophiolite rocks do not respond hydrochemically to geochemical differences. Using ion proportions instead of concentrations, geochemical fingertips of magmatic stream basins were detected. Atmospheric inputs largely affect stream and spring composition, e.g., by 75% regarding sodium. Only 20% of dissolved oxygen and pH variance was assigned to biological activity, while nutrient levels were consistent with the undisturbed conditions of the island, except nitrate. Small mountainous springs and brooks fed by restricted, fractured groundwater aquifers with perennial flow, despite scarce summer rainfalls, may be fueled by cloud and fog condensation. High night-day stream flow differences, high atmospheric humidity predominately occurring during the night, and low stream water travel times point out toward this phenomenon.
Thèses sur le sujet "Rock weathering, Dissolved oxygen":
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Boeder, Michael Karl. « Oxygen Demand Trends, Land Cover Change, and Water Quality Management for an Urbanizing Oregon Watershed ». PDXScholar, 2006. https://pdxscholar.library.pdx.edu/open_access_etds/2236.
Résumé :
In-stream aquatic habitat depends on adequate levels of dissolved oxygen. Human alteration of the landscape has an extensive influence on the biogeochemical processes that drive oxygen cycling in streams. Historic datasets allow researchers to track trends in chemical parameters concomitant with urbanization, while land cover change analysis allows researchers to identify linkages between water quality trends and landscape change.
Using the Seasonal Kendall's test, I examined water quality trends in oxygen demand variables during the mid-1990s to 2003, for twelve sites in the Rock Creek sub-watershed of the Tualatin River, northwest Oregon. Significant trends occurred in each parameter. Dissolved oxygen (DO (%sat)) increased at five sites. Chemical oxygen demand (COD) decreased at seven sites. Total Kjeldahl nitrogen (TKN) decreased at five sites and increased at one site. Ammonium (NH3-N) decreased at one site and increased at one site. Multiple linear regression indicates that nitrogenous oxygen demand accounts for a significant amount of variance in COD at ten of the twelve sites (adjusted R2values from 0.14 to 0.73).
Aerial photo interpretation revealed significant land cover change in agricultural land cover (-8% for the entire basin area) and residential land cover (+10% for the entire basin area). Correlation results between seasonal oxygen demand data and land cover values at multiple scales indicated that: (I) forest cover negatively influences COD at the full sub-basin scale and positively influences NH3-N at local scales, (2) residential land cover positively influences DO (%sat) values at local scales, (3) agricultural land cover does not influence oxygen demand at any land cover assessment scale, ( 4) local topography negatively influences TKN and NH3-N, and (5) urban runoff management infrastructure correlates positively with COD. Study results indicate that, with the exception of forested land, local scale land cover and landscape variables dominate influence on oxygen demand in the Rock Creek basin. Since DO conditions have improved in these streams, watershed management efforts should emphasize local influences in order to continue to maintain stream health.
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Jansen, Nils [Verfasser]. « Chemical rock weathering in North America as source of dissolved silica and sink of atmospheric CO2 / vorgelegt von Nils Jansen ». 2010. http://d-nb.info/1003016820/34.
Livres sur le sujet "Rock weathering, Dissolved oxygen":
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Reed, Green W., Missouri. Dept. of Conservation. et Geological Survey (U.S.), dir. Simulation of hydrodynamics, temperature, and dissolved oxygen in Table Rock Lake, Missouri, 1996-1997. Rolla, Mo : U.S. Dept. of the Interior, U.S. Geological Survey, 2003.
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Ellam, Rob. 7. Reconstructing the past and weathering the future. Oxford University Press, 2016. http://dx.doi.org/10.1093/actrade/9780198723622.003.0007.
Résumé :
Tiny microfossils called Foraminifera form calcium carbonate shells that record the δ18O composition of the seawater in which they grew. These microfossils are found in sea bed sediment cores, and a lot of information from these oxygen isotope records can be extracted. ‘Reconstructing the past and weathering the future’ looks at the methodology used in palaeoclimate studies and explains gain and phase modelling and Milankovitch orbital cycles. Similar isotope temperature records have been constructed from polar ice cores. Atmospheric CO2 composition can be reconstructed from the amount of CO2 dissolved in the ice. A new sub-discipline of clumped isotope geochemistry—‘isotomics’—will have applications far beyond carbonate palaeothermometry.
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Canfield, Donald Eugene. Earth’s Middle Ages : What Came after the GOE. Princeton University Press, 2017. http://dx.doi.org/10.23943/princeton/9780691145020.003.0009.
Résumé :
This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.
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Vaughan, David. 4. Earth’s surface and the cycling of minerals. Oxford University Press, 2014. http://dx.doi.org/10.1093/actrade/9780199682843.003.0004.
Résumé :
‘Earth’s surface and the cycling of minerals’ considers the rock cycle, which has two parts. The first is driven by the heat coming from the Earth’s interior and involves interactions between the mantle and crust. The second is driven primarily by heat from the Sun and involves interactions between exposed crust and the waters of the hydrosphere or gases of the atmosphere. Minerals in these exposed rocks may be dissolved during weathering, or be transported in the flowing water of streams and rivers, by glaciers, or as fine mineral dusts in the atmosphere, eventually being deposited elsewhere as sediments. The rock cycle also impacts on pollution and global warming.
Chapitres de livres sur le sujet "Rock weathering, Dissolved oxygen":
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Bethke, Craig M. « Acid Drainage ». Dans Geochemical Reaction Modeling. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195094756.003.0027.
Résumé :
Acid drainage is a persistent environmental problem in many mineralized areas. The problem is especially pronounced in areas that host or have hosted mining activity (e.g., Lind and Hem, 1993), but it also occurs naturally in unmined areas. The acid drainage results from the weathering of sulfide minerals that oxidize to produce hydrogen ions and contribute dissolved metals to solution. These acidic waters are toxic to plant and animal life, including fish and aquatic insects. Streams affected by acid drainage may be rendered nearly lifeless, their stream beds coated with unsightly yellow and red precipitates of oxy-hydroxide minerals. In some cases, the heavy metals in acid drainage threaten water supplies and irrigation projects. Where acid drainage is well developed and extensive, the costs of remediation can be high. In the Summitville, Colorado district (USA), for example, efforts to limit the contamination of fertile irrigated farmlands in the nearby San Luis Valley and protect aquatic life in the Alamosa River will cost an estimated $100 million or more (Plumlee, 1994a). Not all mine drainage, however, is acidic or rich in dissolved metals (e.g., Ficklin et al., 1992; Mayo et al., 1992; Plumlee et al., 1992). Drainage from mining districts in the Colorado Mineral Belt ranges in pH from 1.7 to greater than 8 and contains total metal concentrations ranging from as low as about 0.1 mg/kg to more than 1000 mg/kg. The primary controls on drainage pH and metal content seem to be (1) the exposure of sulfide minerals to weathering, (2) the availability of atmospheric oxygen, and (3) the ability of nonsulfide minerals to buffer acidity. In this chapter we construct geochemical models to consider how the availability of oxygen and the buffering of host rocks affect the pH and composition of acid drainage. We then look at processes that can attenuate the dissolved metal content of drainage waters. Acid drainage results from the reaction of sulfide minerals with oxygen in the presence of water. As we show in this section, water in the absence of a supply of oxygen gas becomes saturated with respect to a sulfide mineral after only a small amount of the mineral has dissolved.
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Juo, Anthony S. R., et Kathrin Franzluebbers. « Soil Formation and Classification ». Dans Tropical Soils. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195115987.003.0010.
Résumé :
Soil is the superficial layer of the land area of the Earth and contains weathered inorganic materials, organic matter, air, and water. The branch of soil science that studies the formation and classification of soils is termed pedology. For both scientific and technical purposes, soils around the world are organized into various categories on the basis of their differences and similarities. There are two types of soil classification schemes: (i) the scientific or pedological classification schemes which group soils on the basis of morphological, physical, chemical, and mineralogical properties as well as stage of weathering; and (ii) the technical or practical classification schemes which group soils based on selected properties for specific applications in agriculture and urban development, such as making a quick appraisal of soil fertility capability of farmlands or determining the suitability of septic tank installations of a housing development site. Soils are formed from the weathering of rocks and rock debris that have been eroded and transported by water, wind, ice, or gravity to other sites within the landscape. The soil, together with any underlying weathered debris and/or weathered bedrock, is termed regolith. The formation of soils from rock and minerals may take a long period of time, that is, thousands or millions of years. The pathways of soil formation are shown in fig. 7-1. The development of distinct characteristics of a soil profile or pedon involves physical, chemical, and biological weathering processes. The weathering process that involves the breakdown of rock and minerals by the action of water, pressure, heat, and freeze, into increasingly smaller fragments or particles is called physical weathering. The processes that involve hydrolysis, dissolution, and the formation of secondary minerals, such as clay-sized layer silicates and Fe and Al oxides, are called chemical weathering. The two important and interrelated chemical processes of tropical weathering are desilication and laterization. Desilication involves the dissolution of silicate minerals, and the subsequent leaching of dissolved silica from the soil profile by rain. The loss of silica from the soil eventually leads to the formation and accumulation of Fe and Al oxides in the soil, a weathering process known as laterization.
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Maltman, Alex. « Weathering, Soil, and the Minerals in Wine ». Dans Vineyards, Rocks, and Soils. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190863289.003.0014.
Résumé :
Weathering of rocks is the crucial first step in making vineyards possible. For where the debris produced by weathering—the sediment we met in Chapter 5—becomes mixed with moist humus, it will be capable of supporting higher plant life. And thus we have soil, that fundamental prerequisite of all vineyards, indeed of the world’s agriculture. So how does this essential process of weathering come about? Any bare rock at the Earth’s surface is continually under attack. Be it a rocky cliff, a stone cathedral, or a tombstone, there will always be chemical weathering—chemical reactions between its surface and the atmosphere A freshly hewn block of building stone may look indestructible, but before long it will start to look a bit discolored and its surface a little crumbly. We are all familiar with an analogy of this: a fresh surface of iron or steel reacting with moisture and oxygen in the air to form the coating we call rust. In his “Guide to the Lakes” of England, William Wordsworth put the effects of weathering far more picturesquely: “elementary particles crumbling down, over-spread with an intermixture of colors, like the compound hues of a dove’s neck.” A weathered rock is one that is being weakened, broken down. The rock fragments themselves are further attacked, which is why stones in a vineyard often show an outer coating of discolored material, sometimes referred to as a weathering rind (Figure 9.1; see Plate 22). If the stone is broken open, it may show multiple zones of differing colors paralleling the outer surface of the fragment and enclosing a core of fresh rock. Iron minerals soon weather to a powdery combination of hematite, goethite, and limonite, and the rock takes on a reddish-brown, rusty-looking color. The great example of such weathering in viticulture is the celebrated terra rossa, but the rosy soils in parts of Western Australia and places further east such as McLaren Vale and the Barossa Valley are also due to iron minerals. Several Australian wines take their names from this “ironstone.”
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Rickard, David. « Acid Earth ». Dans Pyrite. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190203672.003.0011.
Résumé :
The atmosphere and much of the rivers, lakes, and oceans of the Earth are oxygenated. Any pyrite that comes into contact with these environments becomes unstable and breaks down. The process is called oxidation. It is an exothermic process and, as described in Chapter 5, this process was thought to heat the Earth. It is the opposite of reduction, which we discussed with regard to the microbial formation of sulfide from sulfate in Chapter 6. The counterintuitive concept important here is that oxidation is a chemical process that does not necessarily need oxygen. This idea—that you can oxidize things in the absence of oxygen—is one that most natural scientists are aware of but that they need a couple of nudges occasionally to remind themselves about. This means that pyrite oxidizes not only in oxygenated environments—although that is what we are most familiar with—but also in oxygen-free environments. Among the products of pyrite oxidation are large quantities of acid. Although this happens naturally during rock weathering, the intervention of humankind has led to an enormous increase in the exposure of pyrite to the atmosphere. This has produced contamination of the atmosphere, groundwater, and watercourses on a regional scale. It has also increased the amount of uncontrolled coal burning in coal seams, coal mines, and coal waste tips worldwide, making whole towns uninhabitable and laying waste to large areas. In this chapter I consider in more detail what exactly the process of pyrite oxidation is and how it affects the Earth’s environment today, as well as the problems it stores up for humanity in the future. In chemical terms, oxidation does not mean just the addition of oxygen. Oxidation is a reaction that involves the removal of one or more electrons from a compound because of a chemical reaction. One of the most familiar oxidation reactions is combustion, where substances burn in air to produce heat. The way to put out such a fire is to restrict oxygen access using a chemical foam or fire blanket. Since this reaction with oxygen was the best known, the process was called originally called oxidation.
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Holbourn, Ann, Wolfgang Kuhnt, Karlos G. D. Kochhann, Kenji M. Matsuzaki et Nils Andersen. « Middle Miocene climate–carbon cycle dynamics : Keys for understanding future trends on a warmer Earth ? » Dans Understanding the Monterey Formation and Similar Biosiliceous Units across Space and Time. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.2556(05).
Résumé :
ABSTRACT The late early to middle Miocene period (18–12.7 Ma) was marked by profound environmental change, as Earth entered into the warmest climate phase of the Neogene (Miocene climate optimum) and then transitioned to a much colder mode with development of permanent ice sheets on Antarctica. Integration of high-resolution benthic foraminiferal isotope records in well-preserved sedimentary successions from the Pacific, Southern, and Indian Oceans provides a long-term perspective with which to assess relationships among climate change, ocean circulation, and carbon cycle dynamics during these successive climate reversals. Fundamentally different modes of ocean circulation and carbon cycling prevailed on an almost ice-free Earth during the Miocene climate optimum (ca. 16.9–14.7 Ma). Comparison of δ13C profiles revealed a marked decrease in ocean stratification and in the strength of the meridional overturning circulation during the Miocene climate optimum. We speculate that labile polar ice sheets, weaker Southern Hemisphere westerlies, higher sea level, and more acidic, oxygen-depleted oceans promoted shelf-basin partitioning of carbonate deposition and a weaker meridional overturning circulation, reducing the sequestration efficiency of the biological pump. X-ray fluorescence scanning data additionally revealed that 100 k.y. eccentricity-paced transient hyperthermal events coincided with intense episodes of deep-water acidification and deoxygenation. The in-phase coherence of δ18O and δ13C at the eccentricity band further suggests that orbitally paced processes such as remineralization of organic carbon from the deep-ocean dissolved organic carbon pool and/or weathering-induced carbon and nutrient fluxes from tropical monsoonal regions to the ocean contributed to the high amplitude variability of the marine carbon cycle. Stepwise global cooling and ice-sheet expansion during the middle Miocene climate transition (ca. 14.7–13.8 Ma) were associated with dampening of astronomically driven climate cycles and progressive steepening of the δ13C gradient between intermediate and deep waters, indicating intensification and vertical expansion of ocean meridional overturning circulation following the end of the Miocene climate optimum. Together, these results underline the crucial role of the marine carbon cycle and low-latitude processes in driving climate dynamics on an almost ice-free Earth.
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Thomas, Fabien, et Armand Masion. « 27Al NMR Study of the Hydrolysis and Condensation of Organically Complexed Aluminum ». Dans Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0015.
Résumé :
Aluminum is the most abundant metal of the Earth’s crust, of which it represents approximately 8%, ranking after oxygen and silicon. It exists mainly as oxides. In terrestrial environments, aluminum commonly exists as secondary (authigenic) hydroxide or aluminosilicate minerals, mainly clays. These minerals are highly insoluble at neutral pH. However, aluminum occurs in detectable amounts in natural waters, due to leaching of the soil minerals in acidic conditions. Soil acidity may have a natural origin, such as an acidic (silicic) mother rock, melted snow, dissolved carbonic acid, or biologically generated organic acids. During the past two decades, it has been demonstrated that one of the major origins of increased aluminum mobilization and transport in forested soils is introduction of strong acid through atmospheric sulfur and nitrogen deposition. It has also been shown that aqueous aluminum is the biogeochemical link between atmospheric pollution and damage caused to tree roots and aquatic organisms such as plankton, crustaceans, insects, and fish. Biological studies have shown that the different aluminum species exhibit various toxicities: the most toxic are the monomeric and the polynuclear species; complexation with organic acids results in low toxicity. The significance of aluminum to human health has long been regarded as negligible. There is a possible link between high-level aluminum contamination by renal dialysis or hemodialysis, and neurodegenerative health disorders such as Parkinson’s or Alzheimer’s diseases, but the part played by aluminum is not clear. However, since aluminum salts are used on an industrial level as coagulants and flocculants in water treatment, the aluminum concentration and speciation in drinking water deserve careful monitoring. Because of the specific toxicity of the aluminum species, there has been considerable concern in the past two decades over the speciation of aqueous aluminum present in soils and aquatic systems. To this end, several techniques have been developed in order to partition the aluminum species. The most common among them are chromatographic separation and categorization methods such as timed ferron reaction, and computational methods derived from thermodynamic equilibrium constants. However, significant discrepancies between the results have been noticed, and attributed to the dramatic interference of organic and inorganic anions in the Al fractionation.
Actes de conférences sur le sujet "Rock weathering, Dissolved oxygen":
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Harshbarger, E. Dean, Bethel Herrold, George Robbing et James C. Carter. « Turbine Venting for Dissolved Oxygen Improvements at Bull Shoals, Norfork, and Table Rock Dams ». Dans Waterpower Conference 1999. Reston, VA : American Society of Civil Engineers, 1999. http://dx.doi.org/10.1061/40440(1999)44.
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Kraemer, Dennis, et Michael Bau. « Effects of solution pH, atmospheric oxygen concentrations and weathering state on the mobilization of redox-sensitive trace elements during water-rock interaction in presence of siderophores ». Dans Goldschmidt2021. France : European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.5124.
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Yamamoto, Shuichi, Kenichiro Suzuki, Mamoru Kumagai, Yasuhiro Tawara et Koji Mori. « Gas Transport Properties of Pumice Tuff for Performance Assessment of LLW Disposal Facility ». Dans ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2011. http://dx.doi.org/10.1115/icem2011-59074.
Résumé :
In Japan, some of the radioactive waste with a relatively higher radioactivity concentration from nuclear facilities is to be packaged in rectangle steel containers and disposed of in sub-surface disposal facilities, where normal human intrusion is unlikely to occur. If dissolved oxygen in pore water is consumed by steel corrosion after the closure of the facility, hydrogen gas will be generated from the metallic waste, steel containers and concrete reinforcing bars largely by anaerobic corrosion. If the generated gas accumulates and the gas pressure increases excessively in the facility, the facility’s barrier performance might be degraded by mechanical influences such as fracturing of surrounding rock and cementitious materials or plastic deformation of the bentonite buffer. In this study laboratory experiments for gas and water transport properties of the rock were performed to evaluate gas flow through the rock mass (pumice tuff) around a facility for low level waste disposal. Based on the experimental results two-phase flow properties were evaluated by means of an inverse analysis method. The pumice tuff was subjected to hydraulic conductivity tests, water retention (moisture characteristic) tests, and gas injection tests. Non-linear properties such as relative permeability and water retention curve and hydraulic conductivity as a function of confined stress obtained from these tests are discussed. It was possible to estimate the intrinsic permeability, the relative permeability for gas and water and the water retention curve by applying an inverse analysis method using the multi-phase flow analysis code GETFLOWS and universal sensitivity analysis code UCODE_2005 to the gas injection tests. It was found from this study that gas flow in the pumice tuff is reasonably well described by classical two-phase flow concepts and that the two-phase flow properties can be applied to performance assessment of the facility with regard to the influence of gas generation and migration.
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Bryndzia, L. Taras, et Mathew C. Fay. « Geochemical Analysis of Returned Treatment Waters (RTW) Associated With Shale Gas Production in the Appalachian Basin (USA) and Deep Basin (Canada) : Potential Use of Total Dissolved Solids (TDS) and Oxygen Isotope Data for Assessing Water:Rock Ratios and Stimulated Rock Volume (SRV) ». Dans Unconventional Resources Technology Conference. Tulsa, OK, USA : American Association of Petroleum Geologists, 2016. http://dx.doi.org/10.15530/urtec-2016-2455905.
Rapports d'organisations sur le sujet "Rock weathering, Dissolved oxygen":
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Hackbarth, Carolyn, et Rebeca Weissinger. Water quality in the Northern Colorado Plateau Network : Water years 2016–2018 (revised with cost estimate). National Park Service, novembre 2023. http://dx.doi.org/10.36967/nrr-2279508.
Résumé :
Water-quality monitoring in National Park Service units of the Northern Colorado Plateau Network (NCPN) is made possible through partnerships between the National Park Service Inventory & Monitoring Division, individual park units, the U.S. Geological Survey, and the Utah Division of Water Quality. This report evaluates data from site visits at 62 different locations on streams, rivers, and reservoirs in or near ten NCPN park units between October 1, 2015 and September 30, 2018. Data are compared to state water-quality standards for the purpose of providing information to park managers about potential water-quality problems. The National Park Service does not determine the regulatory status of surface waters; state water quality agencies determine whether waters comply with the Clean Water Act. Evaluation of water-quality parameters relative to state water-quality standards indicated that 17,997 (96.8%) of the 18,583 total designated beneficial-use evaluations completed for the period covered in this report met state water-quality standards. The most common exceedances or indications of impairment, in order of abundance, were due to elevated nutrients, elevated bacteria (E. coli), elevated water temperature, elevated trace metals, elevated total dissolved solids (and sulfate), elevated pH, and low dissolved oxygen. While some exceedances were recurring and may have been caused by human activities in the watersheds, many were due to naturally occurring conditions characteristic of the geographic setting. This is most apparent with phosphorus, which can be introduced into surface water bodies at elevated levels by natural weathering of the geologic strata found throughout the Colorado Plateau. Higher phosphorus concentrations could also be attributed to anthropogenic activities that can accelerate erosion and transport of phosphorus. Some activities that can increase erosional processes include grazing, logging, mining, pasture irrigation, and off-highway vehicle (OHV) use. Exceedances for total phosphorus were common occurrences at nine out of ten NCPN park units, where at least one site in each of these parks had elevated phosphorus concentrations. At these sites, high levels of nutrients have not led to algal blooms or other signs of eutrophication. Sites monitored in Arches National Park (NP), Black Canyon of the Gunnison NP (BLCA), Bryce Canyon NP (BRCA), Capitol Reef NP (CARE), Curecanti National Recreation Area (CURE), Dinosaur National Monument (DINO), and Zion NP (ZION) all had E. coli ex-ceedances that could be addressed by management actions. While many of these sites already have management actions underway, some of the actions necessary to bring these waters into compliance are beyond the control of the National Park Service. Changes to agricultural practices to improve water quality involves voluntary participation by landowners and/or grazing permittees and their respective states. This could be the case with lands upstream of several parks with E. coli contamination issues, including Red Rock Canyon (BLCA); Sul-phur, Oak, and Pleasant creeks (CARE); Blue Creek and Cimarron River (CURE); Brush and Pot creeks (DINO); and North Fork Virgin River (ZION). Issues with E. coli contamination at Yellow Creek (BRCA) seemed to be resolved after the park boundary fence downstream of the site was repaired, keeping cattle out of the park. At North Fork Virgin River, E. coli exceedances have been less frequent since the State of Utah worked with landowners and grazing permittees to modify agricultural practices. Continued coordination between the National Park Service, state agencies, and local landowners will be necessary to further re-duce E. coli exceedances and, in turn, improve public health and safety in these streams. Selenium concentrations in Red Rock Canyon (BLCA) continued to exceed the state aquat-ic-life standard at both the upstream and downstream sites. Although selenium weathers naturally from bedrock and...
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Simulation of hydrodynamics, temperature, and dissolved oxygen in Table Rock Lake, Missouri, 1996-1997. US Geological Survey, 2003. http://dx.doi.org/10.3133/wri034237.