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1
Chigira, Masahiro. "Dissolution and oxidation of mudstone under stress." Canadian Geotechnical Journal 30, no. 1 (February 1, 1993): 60–70. http://dx.doi.org/10.1139/t93-006.
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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.
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Burt, Emily I., Markus Bill, Mark E. Conrad, Adan Julian Ccahuana Quispe, John N. Christensen, Robert G. Hilton, Mathieu Dellinger, and A. Joshua West. "Conservative transport of dissolved sulfate across the Rio Madre de Dios floodplain in Peru." Geology 49, no. 9 (May 19, 2021): 1064–68. http://dx.doi.org/10.1130/g48997.1.
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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, and 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 (January 31, 2024): 271–99. http://dx.doi.org/10.5194/esurf-12-271-2024.
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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, and J. O. P. Pedersen. "Presentation, calibration and validation of the low-order, DCESS Earth System Model." Geoscientific Model Development Discussions 1, no. 1 (June 23, 2008): 39–124. http://dx.doi.org/10.5194/gmdd-1-39-2008.
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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, and J. O. Pepke Pedersen. "Presentation, calibration and validation of the low-order, DCESS Earth System Model (Version 1)." Geoscientific Model Development 1, no. 1 (November 6, 2008): 17–51. http://dx.doi.org/10.5194/gmd-1-17-2008.
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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, and 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 (May 18, 2020): 455. http://dx.doi.org/10.3390/min10050455.
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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, and 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 (October 10, 2021): 46–54. http://dx.doi.org/10.3126/njst.v20i1.39390.
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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, and MINIK T. ROSING. "BIOLOGICAL EFFECTS ON THE SOURCE OF GEONEUTRINOS." International Journal of Modern Physics A 28, no. 30 (December 4, 2013): 1330047. http://dx.doi.org/10.1142/s0217751x13300470.
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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.
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Yang, Haijiao, Jiahua Wei, and Kaifang Shi. "Hydrochemical and Isotopic Characteristics and the Spatiotemporal Differences of Surface Water and Groundwater in the Qaidam Basin, China." Water 16, no. 1 (December 31, 2023): 169. http://dx.doi.org/10.3390/w16010169.
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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, and Sofia Laschou. "Unraveling Aquatic Quality Controls of a Nearly Undisturbed Mediterranean Island (Samothraki, Greece)." Water 12, no. 2 (February 10, 2020): 473. http://dx.doi.org/10.3390/w12020473.
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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.
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Lynnyk, P. M. "Potential Impact of Climate Change on Mineralization and Main Ions Ratio in Surface Fresh Waters (a Review)." Hydrobiological Journal 59, no. 4 (2023): 83–97. http://dx.doi.org/10.1615/hydrobj.v59.i4.70.
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The article deals with problem of the fresh waters salinization in view of its relevance for normal functioning of the aquatic ecosystems, development of different branches of industry and agriculture, and human health. Attention is focused on the fact that the fresh waters' salinization inevitably results in decrease of the ecosystem services scope. The main factors and anthropogenic sources of influence on total dissolved solids in the fresh waters and metamorphosis of their ion composition are considered. It is stated that climate changes potentially affect and will affect the surface waters mineralization in future owing to volume and frequency of the atmospheric precipitation, intensity of the rocks and minerals weathering, the ground feeding of the rivers, the marine water penetration into the estuaries along with reducing of the river water yield, etc. The possible impact of mineralization changes on migration of substances from bottom sediments into the water thickness, that is on the intensity of its secondary pollution, is discussed. This impact can be direct and indirect. First of all, it concerns the migration ability of metals in bottom sediments. Elevated content of Na<sup>+</sup>, Ca<sup>2+</sup> and Mg<sup>2+</sup> in water intensifies migration of metals of the exchangeable fraction of bottom sediments. The indirect effect of elevated mineralization is expressed in the oxygen regime of the water bodies, which usually deteriorates in the near-bottom water layers of deep lakes and reservoirs, mouth areas of the rivers and estuaries. The dissolved oxygen deficit becomes usual, anoxic conditions are formed, which favor release of Fe(III) and Mn(IV) from oxyhydroxides or the oxide fraction of the bottom sediments. A review also considers some aspects of potential impact of the fresh waters salinization on survival of the aquatic plants and animals and biodiversity.
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Bu, Jianwei, Ziyong Sun, Rui Ma, Yunde Liu, Xulong Gong, Zhao Pan, and Wenhao Wei. "Shallow Groundwater Quality and Its Controlling Factors in the Su-Xi-Chang Region, Eastern China." International Journal of Environmental Research and Public Health 17, no. 4 (February 16, 2020): 1267. http://dx.doi.org/10.3390/ijerph17041267.
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Understanding factors influencing groundwater quality is critical to the development of best management practices at the large watershed scale. In this study, the shallow groundwater (10–20 m depth) in the Su-Xi-Chang region, eastern China, was investigated as part of a monitoring program from 2007 to 2008 to analyze the regional groundwater quality as well as the hydrogeochemical processes and their controlling factors. Conventional physicochemical water parameters (pH, turbidity, electrical conductivity, dissolved oxygen, total phosphorus), major cations (Na+, Ca2+, Mg2+ and NH4+) and anions (Cl−, NO3− and SO42−) were measured. Hydrochemical methods and multivariate statistical methods were applied to analyze the hydrogeochemical signatures, origins, the similarities among the variables and to identify the main pollution sources in the groundwater. The results showed that (1) the concentrations of TDS (224.89–1086.70 mg/L) and turbidity (0.1–18.60 NTU) were higher than the class II groundwater quality standards in China and the WHO drinking water standards, (2) there were extremely high concentrations of ammonia (0.01–32.90 mg/L), with a mean value of 0.72 mg/L and (3) the nitrate concentrations (average value of 22.07 mg/L) exceeded the class III groundwater quality standards. The study also provided evidence that weathering, dissolution of carbonate, halite and silicate and cation exchange were the possible primary hydrogeochemical control mechanisms in the groundwater. The sources of ammonia, total phosphorus, sulfates and nitrates included rock–water interactions and anthropogenic activities. The groundwater administration of pollution sinks and sources, long-term legal frameworks and economic incentives should be improved to optimize watershed scale management in the context of rapid development in China.
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Basumatary, Binay Kumar. "Quality of Soil in Gossaigaon Sub-Division and Its Impact on Environmental Degradation." Current Agriculture Research Journal 9, no. 3 (December 31, 2021): 188–95. http://dx.doi.org/10.12944/carj.9.3.06.
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People on Earth are under tremendous threat due to undesired changes in the physical, chemical and biological characteristics of water and soil. Due to increased human population, industrialization, use of unwanted amounts of fertilizers and man-made activities, water and soil is highly polluted with different harmful contaminants. Natural water and soil contaminates due to weathering of rocks and leaching of soils, mining processing etc. It is necessary that the quality of drinking water and soil should be checked at regular time interval, because due to use of contaminated drinking water, human population suffers from variety of water borne diseases. The study area, Gossaigaon sub-division of Kokrajhar district, Assam lies on the north bank of the Brahmaputra river and is slowly sloping towards south from the foothills of Bhutan upto an average height of 42 MSL. The tributaries of the Brahmaputra- Sankosh, Ripu, Dambra, Bura chara, Gadadhar, Gurufella, Madati, Hel, Gongea are flowing southward which have their sources in the Himalayas. In this paper an attempt has been made to assess the quality of soil of 10 different stations by considering the parameters like Colour, Temperature, pH value, Conductance, Alkalinity, Dissolved Oxygen, Hardness, TS, TDS, Chlorine, Fluorine, Sulphur, Nitrogen, Phosphorous, Iron, Calcium and Magnesium, Sodium, Potassium, Zinc, Nickel, Lead and Copper which have direct correlation with human health.
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Kotlia, Bahadur Singh, and Shahditta Bakshi. "Groundwater Assessment in Udham Singh Nagar, Uttarakhand, India Using Multivariate Statistical Techniques, WQI, and HPI." Current World Environment 18, no. 3 (January 10, 2024): 968–83. http://dx.doi.org/10.12944/cwe.18.3.06.
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We conducted a study to assess the variations in groundwater quality and metal pollution and identify the sources in the U S Nagar district of Uttarakhand state of India using multivariate statistical techniques. The two essential indicators of any developed society are Safe drinking water and decontamination. This research aims to undertake drinking water quality analyses of the groundwater and the sources of contamination in Udham Singh Nagar district, Uttarakhand. We produced results of 250 samples collected from hand pumps (Govt. and Private) and artesian wells. We measured 19 parameters which nine physicochemical parameters (pH, electrical conductivity, total dissolved solids, dissolved oxygen, oxidation and reduction potential, salinity, fluoride, chloride, nitrate), 7 Heavy metals (Lead, nickel, chromium, copper, iron, manganese, zinc) along with three metals (potassium, magnesium, sodium). Water quality index, Heavy metal pollution index, PCA (Principal component analysis)/FA (factor analysis), and CA (Cluster analysis) methods were applied. WQI index shows five samples (2 %) comes under the excellent, 211 samples (84.4 %) fall under good quality, and 34 samples (13.6 %) have poor water quality wqi status as per Yadav index. Further, referring to the Ramakrishnaiah index, 216 samples (86.4 %) fall under excellent quality and only 13 samples (13.6 %) come under good water quality. For HPI, as per Indian Standard, nearly 40.4% of samples show a low degree of pollution, 33.2% of samples show a medium degree of pollution, and 26.4% show a High degree of pollution. According to the International HPI standard, 46% of samples show a low degree of pollution, 38% have a medium degree, and 16% show a high-grade degree of pollution. The results of PCA show that groundwater has mainly geogenic (geochemical alteration and weathering of source rock like carbonate, dolomite, quartzite, etc.) followed by anthropogenic sources (agrogenic, domestic sewage and industrial wastes etc.). The results obtained through the PCA are also moderately supported by Cluster analysis. The cations which were over the limit in groundwater samples are presented in chronological order Fe > Pb > Ni > Mg > Mn > Zn > Cu, and significant anions were over the limit F¯ > Cl¯, and the rest was under the limit. The highly heavy metal-contaminated drinking groundwater sample, being used for drinking purpose, is deteriorating and need a proper treatment strategy before domestic water supply.
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Bariteau, Anne, and Medard Thiry. "Analyse et simulation des transferts geochimiques au sein d'un aquifere; la nappe de Beauce et l'alteration des Sables de Fontainebleau." Bulletin de la Société Géologique de France 172, no. 3 (May 1, 2001): 367–81. http://dx.doi.org/10.2113/172.3.367.
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Abstract Ground-water mineralisation results mainly from alteration of the confining aquifer along its flow path. Such alteration may deeply alter the aquifer formations and have to be recognized to avoid misinterpretation of the altered facies. The Beauce ground-water and the Fontainebleau Sands aquifer have been studied to highlight such ground-water/aquifer interactions. The Beauce ground-water is contained in thick limestone series (Oligo-Miocene) interlayered with the Fontainebleau Sands (Stampian). The sands show various facies related to the geomorphology: dark and reduced facies are restricted to the bottom of the formation in the center of the plateaux, oxidized yellowish facies occur in the vadose zone beneath the plateaux, and bleached white facies at the edge of the plateaux. These facies result from modern alternations due to the ground-water and the recharge waters. The water and rock chemistry allows to investigate the diverse stages of the geochemical and weathering processes that occur within the aquifer, and to calculate accurate mass balance of the dissolved and exported elements. Hydrochemistry of the Beauce ground-water: Each compartment of the aquifer can be characterised by one type of water. (1) The aquifer is recharged by two types of water. The waters coming from the limestone plateau are calco-carbonaceous, oxygenated and lightly mineralised, especially in silica; those coming from the sandy soils near the outcropping sand area are more acidic, oxygenated and very lightly mineralised. (2) The ground-water of the limestone aquifer are oxygenated, oversaturated with respect to quartz and near equilibrium with calcite and cristobalite. Silica comes from the alteration of the clay minerals and/or the cherts in the limestones. The ground-waters are of calco-carbonaceous type, have pH values approx 6.5. They are characterised by a relative low mineralisation (average 460 mg.kg (super -1) ), an oversaturation with respect to quartz and the presence of dissolved oxygen (Eh around +450 mV). (3) The ground-water of the dark sands aquifer contains hydrogen sulfur and is oxygen free (Eh around +140 mV), with relatively high Fe and SO 4 contents related to the pyrite oxidation. It is also characterised by a relatively high SiO 2 and cations contents resulting from the alteration of the alumino-silicates. (4) The ground-water of the bleached sands aquifer is strongly diluted by the recharge waters from the sandy soils. It remains oversaturated with respect to quartz and has the ability to hydrolyse the alumino-silicates. Geochemical modelling: The ground-water/aquifer interactions have been modelled. The modelisation takes into account the kinetics of water/rock interactions and was done by successive steps. (1) Alteration of the dark sands by the ground-water leads to dissolution of the pyrite and the calcite. The pyrite oxidation and the "buffering" calcite dissolution directly depend on oxygen availability in the ground-water. Muscovite remains stable, feldspars and glauconite are partially dissolved and Al-smectite forms. The composition of the resulting simulated oxydized sands agrees with the analyses. (2) The leaching of these oxydized sands by the calco-carbonaceous recharge water leads to simulate leached sands of similar composition than the unsaturated sands beneath the plateau. Muscovite remains stable; smectite, kaolinite and hematite form. (3) The final leaching of the former leached sand by the acidic recharge water brings about to simulate bleached sand. The muscovite stability, smectite dissolution and kaolinite precipitation are in conformity with the composition of the white sands. Nevertheless, the modelisation is not fully in agreement with the mass balance calculations. The discrepancy mainly comes from the simulation of excessive amounts of clay minerals and iron oxides. This precipitation excess may be related to the fact that the precipitation kinetics and/or of the organic complexations have not been taken into account in the model. Even if there is discrepancy in the mass balance, the thermokinetic simulations validate the reaction path which leads to the Beauce ground-water mineralisation and the Fontainebleau Sands bleaching. Discussion: Ground-water chemistry thus provides information on the alteration processes and indicates that the alterations are presently active. The white facies results from the progressive alteration of dark primary sands. This bleaching leads to a complete change of the geochemical characteristics of the Fontainebleau Sands. These alterations come with the export of a large amount of material corresponding to a geochemical lowering of the Beauce Plateau of at least 10 m during the Plio-Quaternary period. This example illustrates the importance of the sub-surface alterations due to ground-water flow, that are difficult to gauge from outcrop observation only.
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Zhang, Liankai, Xiaoqun Qin, Qibo Huang, and Pengyu Liu. "Role of sulfuric acid in chemical weathering of carbonate rocks for evaluating of carbon sinks in the Yangtze River Basin, China." E3S Web of Conferences 98 (2019): 06015. http://dx.doi.org/10.1051/e3sconf/20199806015.
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Chemical weathering of rock by river systems is an important process in the global carbon cycle. Sulfuric acid produced from anthropogenic sources in the Yangtze River basin of China has the potential to change rock weathering processes and the carbon cycle. Monitoring and analysis of the dissolved constituents of the main channel and major tributaries of the Yangtze River indicate that the sulfuric acid has enhanced the carbonate rock weathering rate by an average of 28% and reduced the CO2 consumption rate by 12%. Analysis of dissolved sources for SO42- in the Yangtze River indicates that 36% of SO42- can be attributed to rainwater, 26% to dissolution of evaporitic rocks, and 38% to input from coal. Calculations indicate that the annual output flux of CO2 from the Yangtze River Basin to the sea is 3495×104 tons, 80% of which is attributed to the weathering of carbonate rocks. Whilst the average consumption rate of atmospheric CO2 is 20.6 t/km2 y-1.
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Charbonnier, Quentin, Julien Bouchez, Jérôme Gaillardet, and Éric Gayer. "Barium stable isotopes as a fingerprint of biological cycling in the Amazon River basin." Biogeosciences 17, no. 23 (December 3, 2020): 5989–6015. http://dx.doi.org/10.5194/bg-17-5989-2020.
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Abstract. The biological cycle of rock-derived nutrients on the continents is a major component of element transfer between the Earth's surface compartments, but its magnitude currently remains elusive. The use of the stable isotope composition of rock-derived nutrients, which can be fractionated during biological uptake, provides a promising path forward with respect to quantifying biological cycling and its overall contribution to global element cycling. In this paper, we rely on the nutrient-like behaviour of the trace element barium (Ba) and use its elemental and stable isotope compositions in dissolved and sediment load river samples to investigate biological cycling in the Amazon Basin. From these measurements, we show that dissolved Ba mainly derives from silicate rocks, and a correlation between dissolved Ba and K abundances suggests that biological cycling plays a role in the Ba river budget. Furthermore, the isotope composition of Ba (δ138Ba) in the dissolved load was found to be significantly different from that of the parent silicate rocks, implying that dissolved Ba isotopic signatures are affected by (i) the precipitation of soil-forming secondary phases as well as (ii) biological uptake and release from dead organic matter. Results from an isotope mass balance method applied to the river dissolved load data indicate that, after its release to solution by rock weathering, Ba is partitioned between the river dissolved load, secondary weathering products (such as those found in soils and river sediments), and the biota. In most sub-catchments of the Amazon, river Ba abundances and isotope compositions are significantly affected by biological cycling. Relationships between estimates of Ba cycled through biota and independent metrics of ecosystem dynamics (such as gross primary production and terrestrial ecosystem respiration) allow us to discuss the role of environmental parameters such as climate or erosion rates on the biological cycling of Ba and, by extension, the role of major rock-derived nutrients. In addition, catchment-scale mass and isotope budgets of Ba show that the measured riverine export of Ba is lower than the estimated delivery of Ba to the Earth surface through rock alteration. This indicates the existence of a missing Ba component, which we attribute to the formation of Ba-bearing particulate organics (possibly accumulating as soil organic matter or currently growing biomass within the catchments) and to organic-bound Ba exported as “unsampled” river particulate organic matter. Given our findings on the trace element Ba, we explore whether the river fluxes of most major rock-derived nutrients (K, Mg, Ca) might also be significantly affected by biological uptake or release. A first-order correction of river-derived silicate weathering fluxes from biological cycling shows that the carbon dioxide (CO2) consumption by silicate weathering at the mouth of the Amazon could be several times higher than the previously reported value of 13 × 109 mol CO2 yr−1 (Gaillardet et al., 1997). Overall, our study clearly shows that the chemical and isotope compositions of rivers in the Amazon – and most likely in other large river basins – bear a biological imprint, thereby challenging common assumptions made in weathering studies.
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Emberson, Robert, Niels Hovius, Albert Galy, and Odin Marc. "Oxidation of sulfides and rapid weathering in recent landslides." Earth Surface Dynamics 4, no. 3 (September 22, 2016): 727–42. http://dx.doi.org/10.5194/esurf-4-727-2016.
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Abstract. Linking together the processes of rapid physical erosion and the resultant chemical dissolution of rock is a crucial step in building an overall deterministic understanding of weathering in mountain belts. Landslides, which are the most volumetrically important geomorphic process at these high rates of erosion, can generate extremely high rates of very localised weathering. To elucidate how this process works we have taken advantage of uniquely intense landsliding, resulting from Typhoon Morakot, in the T'aimali River and surrounds in southern Taiwan. Combining detailed analysis of landslide seepage chemistry with estimates of catchment-by-catchment landslide volumes, we demonstrate that in this setting the primary role of landslides is to introduce fresh, highly labile mineral phases into the surface weathering environment. There, rapid weathering is driven by the oxidation of pyrite and the resultant sulfuric-acid-driven dissolution of primarily carbonate rock. The total dissolved load correlates well with dissolved sulfate – the chief product of this style of weathering – in both landslides and streams draining the area (R2 = 0.841 and 0.929 respectively; p < 0.001 in both cases), with solute chemistry in seepage from landslides and catchments affected by significant landsliding governed by the same weathering reactions. The predominance of coupled carbonate–sulfuric-acid-driven weathering is the key difference between these sites and previously studied landslides in New Zealand (Emberson et al., 2016), but in both settings increasing volumes of landslides drive greater overall solute concentrations in streams. Bedrock landslides, by excavating deep below saprolite–rock interfaces, create conditions for weathering in which all mineral phases in a lithology are initially unweathered within landslide deposits. As a result, the most labile phases dominate the weathering immediately after mobilisation and during a transient period of depletion. This mode of dissolution can strongly alter the overall output of solutes from catchments and their contribution to global chemical cycles if landslide-derived material is retained in catchments for extended periods after mass wasting.
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Uhlig, David, Jan A. Schuessler, Julien Bouchez, Jean L. Dixon, and Friedhelm von Blanckenburg. "Quantifying nutrient uptake as driver of rock weathering in forest ecosystems by magnesium stable isotopes." Biogeosciences 14, no. 12 (June 26, 2017): 3111–28. http://dx.doi.org/10.5194/bg-14-3111-2017.
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Abstract. Plants and soil microbiota play an active role in rock weathering and potentially couple weathering at depth with erosion at the soil surface. The nature of this coupling is still unresolved because we lacked means to quantify the passage of chemical elements from rock through higher plants. In a temperate forested landscape characterised by relatively fast (∼ 220 t km−2 yr−1) denudation and a kinetically limited weathering regime of the Southern Sierra Critical Zone Observatory (SSCZO), California, we measured magnesium (Mg) stable isotopes that are sensitive indicators of Mg utilisation by biota. We find that Mg is highly bio-utilised: 50–100 % of the Mg released by chemical weathering is taken up by forest trees. To estimate the tree uptake of other bio-utilised elements (K, Ca, P and Si) we compared the dissolved fluxes of these elements and Mg in rivers with their solubilisation fluxes from rock (rock dissolution flux minus secondary mineral formation flux). We find a deficit in the dissolved fluxes throughout, which we attribute to the nutrient uptake by forest trees. Therefore both the Mg isotopes and the flux comparison suggest that a substantial part of the major element weathering flux is consumed by the tree biomass. The enrichment of 26Mg over 24Mg in tree trunks relative to leaves suggests that tree trunks account for a substantial fraction of the net uptake of Mg. This isotopic and elemental compartment separation is prevented from obliteration (which would occur by Mg redissolution) by two potential effects. Either the mineral nutrients accumulate today in regrowing forest biomass after clear cutting, or they are exported in litter and coarse woody debris (CWD) such that they remain in solid biomass. Over pre-forest-management weathering timescales, this removal flux might have been in operation in the form of natural erosion of CWD. Regardless of the removal mechanism, our approach provides entirely novel means towards the direct quantification of biogenic uptake following weathering. We find that Mg and other nutrients and the plant-beneficial element Si (bio-elements) are taken up by trees at up to 6 m depth, and surface recycling of all bio-elements but P is minimal. Thus, in the watersheds of the SSCZO, the coupling between erosion and weathering might be established by bio-elements that are taken up by trees, are not recycled and are missing in the dissolved river flux due to erosion as CWD and as leaf-derived bio-opal for Si. We suggest that the partitioning of a biogenic weathering flux into eroded plant debris might represent a significant global contribution to element export after weathering in eroding mountain catchments that are characterised by a continuous supply of fresh mineral nutrients.
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Qin, Xiaoqun, Zhongcheng Jiang, Liankai Zhang, Qibo Huang, and Pengyu Liu. "Effects of atmospheric CO2 consumption on rock weathering in the Pearl River basin, China." E3S Web of Conferences 98 (2019): 06011. http://dx.doi.org/10.1051/e3sconf/20199806011.
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Atmospheric CO2 is absorbed and dissolved in water via karst processes not only in carbonate rock areas, but in all rock areas of the earth. The chemical and isotopic analysis results, particularly of strontium, for water samples collected from eleven stations along the Pearl River, four times over the course of one year, showed that due to weathering by carbonate or silicate rocks, HCO3-, Ca2+, and Mg2+ have become the main ions in the river water. Through river ion stoichiometric and flux calculations, the carbonate rock weathering rate and atmospheric CO2 consumption were found to be 27.6 mm/ka and 540 x 103 mol/km2.a, which are 10.8 and 6.7 times the corresponding values for silicate rock. With the beneficial climatic conditions for rock erosion and large areas of carbonate rock in the Pearl River Basin, the atmospheric CO2 consumption value is about 2.6 times the average value for the 60 major rivers in the world.
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Brault, M. O., L. A. Mysak, and H. D. Matthews. "Carbon cycle implications of terrestrial weathering changes since the last glacial maximum." FACETS 2, no. 1 (May 1, 2017): 267–85. http://dx.doi.org/10.1139/facets-2016-0040.
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We examine the importance of the rock weathering feedback mechanism during the last deglacial period (∼16 000–4000 BCE) using an Earth system model of intermediate complexity (the University of Victoria Earth System Climate Model (UVic ESCM)) with four box-model parameterizations of terrestrial weathering. The deglacial climate change is driven by changes in orbital parameters, ice core reconstructions of atmospheric CO2 variability, and prescribed removal of continental ice sheets. Over the course of the 12 000 year simulation period, increases in weathering provide a mechanism that slowly removes CO2 from the atmosphere, in opposition to the observed atmospheric CO2 increase during this period. These processes transfer both carbon and alkalinity to the ocean, the combination of which results in as much as a 1000 Pg C increase in total ocean carbon, relative to a control simulation with constant weathering. However, the rapid expansion of northern hemisphere vegetation introduces a significant uncertainty among the weathering parameterizations. Further experiments to test the individual impacts of weathering dissolved inorganic carbon and alkalinity fluxes on ocean biogeochemistry suggest that the worldwide distribution of rock types and the ratio of carbonate to silicate weathering may be crucially important in obtaining an accurate estimate of changes in global weathering rates.
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Kim, JP, MR Reid, RG Cunninghame, and KA Hunter. "Aqueous chemistry of major ions and trace metals in the Clutha River, New Zealand." Marine and Freshwater Research 47, no. 7 (1996): 919. http://dx.doi.org/10.1071/mf9960919.
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Concentrations of the major ions Na+, K+, Mg2+, Ca2+, HCO32-, SO42- and Cl-, of silicate, and of both total and dissolved trace metals Zn, Cu, Pb and Cd were determined at sites along the Clutha River. The major ions exhibited differing behaviour both spatially and temporally. A large proportion of Cl- and Na+ throughout the catchment could be attributed to atmospheric input of sea salt. Contributions from this source for the rest of the major elements were minimal, except perhaps near the mouth of the river (K+, Mg2+). The water composition was dominated by the weathering of carbonate rather than of silicate minerals. Increases in the concentrations of Mg and Na + K indicate the weathering of Mg, K and Na from rock, minerals and clays within the catchment. The concentrations of major ions and Si were relatively low compared with other rivers in New Zealand and elsewhere. Concentrations of dissolved Zn, Cu, Pb and Cd all increased consistently with distance down river, and between 40% and 100%, for a given metal, was found in the dissolved fraction. High correlation among the dissolved trace metals, with essentially constant Cu : Zn : Pb : Cd ratios of 755 : 716 : 223 : 1 (molar basis), indicates that the same weathering process or source may be occurring throughout the catchment.
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Wu, Huaying, Zhongcheng Jiang, Qibo Huang, Funing Lan, Hongwei Liao, Tengfang Li, and Chenhui Huang. "Geochemistry of Weathering Cover and the Main Influencing Factors in Karst Area of Guilin, Southwest China." Water 15, no. 16 (August 15, 2023): 2944. http://dx.doi.org/10.3390/w15162944.
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The chemical weathering of carbonate rocks is the main form of interaction between earth spheres in the karst critical zone. The karst weathering cover, which is composed by residua from carbonate rocks weathering, contains important information about the climate environment and material cycle. We present the chemical composition of weathering covers in karst area of Guilin, Guangxi province, analyze their weathering process and strength, and compare them with the other weathering covers in other karst area in China, including Yunnan, Guizhou, Hunan, and Qinghai Tibet Plateau. The results showed: (1) the chemical composition of Guilin weathering covers were similar to that of carbonate weathering covers in other areas of China, and had the common characteristics of uniform distribution of chemical composition in the profile and obvious enrichment of Fe, Al and trace elements. During the formation of carbonate weathering cover and the residua, the rapid dissolution of Ca and Mg had an important impact on the migration and enrichment of other elements. (2) The chemical index of alteration (CIA) of carbonate weathering covers in Guilin and other karst areas of China was much larger than that in the upper crust (UCC) (60.13), which showed strong chemical weathering characteristics of the humid and hot climate. (3) The weathering process of carbonate rock was different from that of silicate and loess. In the early stage of carbonate rock weathering, soluble components (calcite and dolomite) had been rapidly dissolved and leached. All the carbonate weathering residua was measured to be in the stage of K2O weathering and Al2O3 increasing. Therefore, the weathering degree of carbonate weathering cover was mainly determined by the leaching of K2O and the increase of Al2O3. As a result, there was no correlation between CIA and Na/K (molar ratio), but was a significant negative correlation between CIA and K/Al (molar ratio) in the carbonate weathering cover. (4) The CIA values of weathering residua and carbonate weathering cover in southern China were negatively correlated with latitude, reflecting the influence of climate factors. From the influence of lithology, the chemical compositions of parent rock can affect the CIA of weathering cover, and the content of insoluble matter in carbonate rock was negatively correlated with CIA. From the influence of topography, the CIA value of weathering residua decreased from the high to the low position and from the shallow to the deep part of the profile.
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Gu, Xin, Peter J. Heaney, Fabio D. A. Aarão Reis, and Susan L. Brantley. "Deep abiotic weathering of pyrite." Science 370, no. 6515 (October 22, 2020): eabb8092. http://dx.doi.org/10.1126/science.abb8092.
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Pyrite is a ubiquitous iron sulfide mineral that is oxidized by trace oxygen. The mineral has been largely absent from global sediments since the rise in oxygen concentration in Earth’s early atmosphere. We analyzed weathering in shale, the most common rock exposed at Earth’s surface, with chemical and microscopic analysis. By looking across scales from 10−9 to 102 meters, we determined the factors that control pyrite oxidation. Under the atmosphere today, pyrite oxidation is rate-limited by diffusion of oxygen to the grain surface and regulated by large-scale erosion and clast-scale fracturing. We determined that neither iron- nor sulfur-oxidizing microorganisms control global pyrite weathering fluxes despite their ability to catalyze the reaction. This multiscale picture emphasizes that fracturing and erosion are as important as atmospheric oxygen in limiting pyrite reactivity over Earth’s history.
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Maavara, Taylor, Erica R. Siirila-Woodburn, Fadji Maina, Reed M. Maxwell, James E. Sample, K. Dana Chadwick, Rosemary Carroll, et al. "Modeling geogenic and atmospheric nitrogen through the East River Watershed, Colorado Rocky Mountains." PLOS ONE 16, no. 3 (March 24, 2021): e0247907. http://dx.doi.org/10.1371/journal.pone.0247907.
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There is a growing understanding of the role that bedrock weathering can play as a source of nitrogen (N) to soils, groundwater and river systems. The significance is particularly apparent in mountainous environments where weathering fluxes can be large. However, our understanding of the relative contributions of rock-derived, or geogenic, N to the total N supply of mountainous watersheds remains poorly understood. In this study, we develop the High-Altitude Nitrogen Suite of Models (HAN-SoMo), a watershed-scale ensemble of process-based models to quantify the relative sources, transformations, and sinks of geogenic and atmospheric N through a mountain watershed. Our study is based in the East River Watershed (ERW) in the Upper Colorado River Basin. The East River is a near-pristine headwater watershed underlain primarily by an N-rich Mancos Shale bedrock, enabling the timing and magnitude of geogenic and atmospheric contributions to watershed scale dissolved N-exports to be quantified. Several calibration scenarios were developed to explore equifinality using >1600 N concentration measurements from streams, groundwater, and vadose zone samples collected over the course of four years across the watershed. When accounting for recycling of N through plant litter turnover, rock weathering accounts for approximately 12% of the annual dissolved N sources to the watershed in the most probable calibration scenario (0–31% in other scenarios), and 21% (0–44% in other scenarios) when considering only “new” N sources (i.e. geogenic and atmospheric). On an annual scale, instream dissolved N elimination, plant turnover (including cattle grazing) and atmospheric deposition are the most important controls on N cycling.
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Han, Tianding, Yuping Li, Jia Qin, Xiangying Li, Qin Yang, and Xiaobo He. "Hydrochemical Changes and Influencing Factors in the Dongkemadi Region, Tanggula Range, China." Water 10, no. 12 (December 14, 2018): 1856. http://dx.doi.org/10.3390/w10121856.
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In order to detect the source and controlling factors of hydrochemical ions in glacier meltwater-recharged rivers, the chemical characteristics of the river water, precipitation, and meltwater of the Dongkemadi River Basin, China, in 2014 (from May to October) were systematically analyzed, and combined with the hydrological and meteorological data. The results show that the hydrochemical pattern of the typical river was HCO3−-Ca2+. The most cations were Ca2+ and Mg2+, and the predominant anions were HCO3− and SO42−, in the river. The concentration of major ions and total dissolved solids (TDS) in the river water were much larger than that in the precipitation and meltwater. The TDS concentration was ordered: River water > precipitation > meltwater. The water-rock interaction and the dilution effect of the precipitation and meltwater on the runoff ions resulted in a negative correlation between the ion concentration of the river water and the river flow. The chemical ions of the river runoff mainly originated from rock weathering and the erosion (abrasion) caused by glacier movement. In addition, the contributions of different sources to the dissolved components of the Dongkemadi River were ordered: Carbonate (75.8%) > silicate (15.5%) > hydatogenic rock (5.7%) > atmospheric precipitation (3%), calculated by a forward geochemical model. And the hydrochemical weathering rates of carbonate and silicate minerals were 12.30 t·km−2·a−1 and 1.98 t·km−2·a−1, respectively. The CO2 fluxes, consumed by the chemical weathering of carbonate and silicate, were 3.28 × 105 mol·km−2·a−1 and 0.91 × 105 mol·km−2·a−1, respectively.
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Li, Dalong, Haiyan Chen, Shaofeng Jia, and Aifeng Lv. "Possible Hydrochemical Processes Influencing Dissolved Solids in Surface Water and Groundwater of the Kaidu River Basin, Northwest China." Water 12, no. 2 (February 10, 2020): 467. http://dx.doi.org/10.3390/w12020467.
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Hydrochemical processes under intense human activities were explored on the basis of the hydrochemical characteristics of 109 surface water samples and 129 groundwater samples collected during August 2015 to September 2016, in the Kaidu River Basin. Results obtained in this study indicated that the water in the basin was neutral to slightly alkaline with low total dissolved solids. Rock weathering and evaporation controlled the natural hydrochemical mechanisms. Mountain groundwater and stream water were dominated by Ca2+-HCO3− type water, whereas the plains groundwater was dominated by mixed type water. The results of principal component analysis demonstrated that water-rock interaction and human activity explained 71.6% and 12.9% of surface water hydrochemical variations, respectively, and 75.1% and 14.2% of groundwater hydrochemical variations, respectively. Sulfate, chloride, and carbonate weathering were the major water-rock interaction processes. Livestock farming and agricultural activities were the primary human activities influencing the water hydrochemistry. In addition, cation exchange is another important process influencing the hydrochemical characteristics in the study area. This study would be helpful in forecasting of water quality in arid areas.
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Zhang, Shitong, Guilin Han, Jie Zeng, Xuhuan Xiao, and Fairda Malem. "A Strontium and Hydro-Geochemical Perspective on Human Impacted Tributary of the Mekong River Basin: Sources Identification, Fluxes, and CO2 Consumption." Water 13, no. 21 (November 8, 2021): 3137. http://dx.doi.org/10.3390/w13213137.
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As the largest and most representative tributary of the Mekong River, the Mun River Basin (MRB) provides critical understanding of regional hydro-geochemical features and rock weathering processes on a basin scale. The present study measured strontium (Sr) isotopes with hydro-geochemistry data of 56 water samples in detail in the MRB in northeast Thailand. The dissolved Sr contents and 87Sr/86Sr isotopic ratios were reported to be 8.7–344.6 μg/L (average 126.9 μg/L) and 0.7085–0.7281 (average 0.7156), respectively. The concentrations of dissolved Sr in the mainstream slightly decreased from upstream to downstream, while the variation trend of 87Sr/86Sr was on the contrary. Correlation analysis showed that Na+ strongly correlated with Cl− (0.995, p < 0.01), while Ca2+ exhibited weak relationships with SO42− (0.356, p < 0.01). Samples of the MRB exhibited lower Mg2+/Na+, Ca2+/Na+, HCO3−/Na+ and 1000Sr/Na ratios, and gathered around the end-member of evaporite dissolution, with slight shift to silicate weathering end-member, demonstrating the dominant contribution of evaporite dissolution and silicate weathering on dissolved loads. Comparing with data of major world rivers from previous research, our results remained consistency with rivers draining through similar geological conditions. The dissolved Sr flux to the adjacent Mekong River was estimated to be 20.7 tons/year. In accordance with the forward model, silicate weathering rate and CO2 consumption rate during dry season were calculated to be 0.73 tons/km2/year and 1.94 × 104 mol/km2/year, and may get underestimated due to intense water consumption by extensive agricultural activities. The superimposed effect of anthropogenic impacts on the water environment could enhance chemical weathering, and thus should be taken into account in regional ion cycles and carbon budgets. These findings highlight the coupling analysis of Sr isotopes and hydro-geochemistry in Earth surface processes and provide basic investigation for sustainable regional water treatment mechanisms in the pan basin of the Mekong River.
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Bufe, Aaron, Kristen L. Cook, Albert Galy, Hella Wittmann, and Niels Hovius. "The effect of lithology on the relationship between denudation rate and chemical weathering pathways – evidence from the eastern Tibetan Plateau." Earth Surface Dynamics 10, no. 3 (June 7, 2022): 513–30. http://dx.doi.org/10.5194/esurf-10-513-2022.
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Abstract. The denudation of rocks in mountain belts exposes a range of fresh minerals to the surface of the Earth that are chemically weathered by acidic and oxygenated fluids. The impact of the resulting coupling between denudation and weathering rates fundamentally depends on the types of minerals that are weathering. Whereas silicate weathering sequesters CO2, the combination of sulfide oxidation and carbonate dissolution emits CO2 to the atmosphere. Here, we combine the concentrations of dissolved major elements in stream waters with 10Be basin-wide denudation rates from 35 small catchments in eastern Tibet to elucidate the importance of lithology in modulating the relationships between denudation rate, chemical weathering pathways, and CO2 consumption or release. Our catchments span 3 orders of magnitude in denudation rate in low-grade flysch, high-grade metapelites, and granitoid rocks. For each stream, we estimate the concentrations of solutes sourced from silicate weathering, carbonate dissolution, and sulfide oxidation using a mixing model. We find that for all lithologies, cation concentrations from silicate weathering are largely independent of denudation rate, but solute concentrations from carbonates and, where present, sulfides increase with increasing denudation rate. With increasing denudation rates, weathering may therefore shift from consuming to releasing CO2 in both (meta)sedimentary and granitoid lithologies. For a given denudation rate, we report dissolved solid concentrations and inferred weathering fluxes in catchments underlain by (meta)sedimentary rock that are 2–10 times higher compared to catchments containing granitoid lithologies, even though climatic and topographic parameters do not vary systematically between these catchments. Thus, varying proportions of exposed (meta)sedimentary and igneous rocks during orogenesis could lead to changes in the sequestration and release of CO2 that are independent of denudation rate.
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Soulet, Guillaume, Robert G. Hilton, Mark H. Garnett, Mathieu Dellinger, Thomas Croissant, Mateja Ogrič, and Sébastien Klotz. "Technical note: In situ measurement of flux and isotopic composition of CO<sub>2</sub> released during oxidative weathering of sedimentary rocks." Biogeosciences 15, no. 13 (July 4, 2018): 4087–102. http://dx.doi.org/10.5194/bg-15-4087-2018.
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Abstract. Oxidative weathering of sedimentary rocks can release carbon dioxide (CO2) to the atmosphere and is an important natural CO2 emission. Two mechanisms operate – the oxidation of sedimentary organic matter and the dissolution of carbonate minerals by sulfuric acid. It has proved difficult to directly measure the rates at which CO2 is emitted in response to these weathering processes in the field, with previous work generally using methods which track the dissolved products of these reactions in rivers. Here we design a chamber method to measure CO2 production during the oxidative weathering of shale bedrock, which can be applied in erosive environments where rocks are exposed frequently to the atmosphere. The chamber is drilled directly into the rock face and has a high surface-area-to-volume ratio which benefits measurement of CO2 fluxes. It is a relatively low-cost method and provides a long-lived chamber (several months or more). To partition the measured CO2 fluxes and the source of CO2, we use zeolite molecular sieves to trap CO2 “actively” (over several hours) or “passively” (over a period of months). The approaches produce comparable results, with the trapped CO2 having a radiocarbon activity (fraction modern, Fm) ranging from Fm = 0.05 to Fm = 0.06 and demonstrating relatively little contamination from local atmospheric CO2 (Fm = 1.01). We use stable carbon isotopes of the trapped CO2 to partition between an organic and inorganic carbon source. The measured fluxes of rock-derived organic matter oxidation (171 ± 5 mgC m−2 day−1) and carbonate dissolution by sulfuric acid (534±16 mgC m−2 day−1) from a single chamber were high when compared to the annual flux estimates derived from using dissolved river chemistry in rivers around the world. The high oxidative weathering fluxes are consistent with the high erosion rate of the study region. We propose that our in situ method has the potential to be more widely deployed to directly measure CO2 fluxes during the oxidative weathering of sedimentary rocks, allowing for the spatial and temporal variability in these fluxes to be determined.
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Lehmann, Nele, Hugues Lantuit, Michael Ernst Böttcher, Jens Hartmann, Antje Eulenburg, and Helmuth Thomas. "Alkalinity generation from carbonate weathering in a silicate-dominated headwater catchment at Iskorasfjellet, northern Norway." Biogeosciences 20, no. 16 (August 18, 2023): 3459–79. http://dx.doi.org/10.5194/bg-20-3459-2023.
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Abstract. The weathering rate of carbonate minerals is several orders of magnitude higher than for silicate minerals. Therefore, small amounts of carbonate minerals have the potential to control the dissolved weathering loads in silicate-dominated catchments. Both weathering processes produce alkalinity under the consumption of CO2. Given that only alkalinity generation from silicate weathering is thought to be a long-term sink for CO2, a misattributed weathering source could lead to incorrect conclusions about long- and short-term CO2 fixation. In this study, we aimed to identify the weathering sources responsible for alkalinity generation and CO2 fixation across watershed scales in a degrading permafrost landscape in northern Norway, 68.7–70.5∘ N, and on a temporal scale, in a subarctic headwater catchment on the mountainside of Iskorasfjellet, characterized by sporadic permafrost and underlain mainly by silicates as the alkalinity-bearing lithology. By analyzing total alkalinity (AT) and dissolved inorganic carbon (DIC) concentrations, as well as the stable isotope signature of the latter (δ13C-DIC), in conjunction with dissolved cation and anion loads, we found that AT was almost entirely derived from weathering of the sparse carbonate minerals. We propose that in the headwater catchment the riparian zone is a hotspot area of AT generation and release due to its enhanced hydrological connectivity and that the weathering load contribution from the uphill catchment is limited by insufficient contact time of weathering agents and weatherable materials. By using stable water isotopes, it was possible to explain temporal variations in AT concentrations following a precipitation event due to surface runoff. In addition to carbonic acid, sulfuric acid, probably originating from oxidation of pyrite or reduced sulfur in wetlands or from acid deposition, is shown to be a potential corrosive reactant. An increased proportion of sulfuric acid as a potential weathering agent may have resulted in a decrease in AT. Therefore, carbonate weathering in the studied area should be considered not only as a short-term CO2 sink but also as a potential CO2 source. Finally, we found that AT increased with decreasing permafrost probability, and attributed this relation to an increased water storage capacity associated with increasing contact of weathering agent and rock surfaces and enhanced microbial activity. As both soil respiration and permafrost thaw are expected to increase with climate change, increasing the availability of weathering agents in the form of CO2 and water storage capacity, respectively, we suggest that future weathering rates and alkalinity generation will increase concomitantly in the study area.
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Larson, Erik B., and Ronald V. Emmons. "Dissolution of Carbonate Rocks in a Laboratory Setting: Rates and Textures." Minerals 11, no. 6 (June 5, 2021): 605. http://dx.doi.org/10.3390/min11060605.
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Determining the dissolution rates of carbonate rocks is vital to advancing our understanding of cave, karst, and landscape processes. Furthermore, the role of carbonate dissolution is important for the global carbon budget and climate change. A laboratory experiment was setup to calculate the dissolution rates of two whole rock carbonate samples with different petrographic makeup (ooids and brachiopods). The carbonate rock samples were also explored under a scanning electron microscope to evaluate the textures that developed after dissolution The oolitic limestone dissolved at a rate of 1579 cm yr−1, and the pentamerous limestone (dolostone) dissolved at a rate of 799 cm yr−1. Both rocks did not dissolve evenly across their surface as indicated by scanning electron microscopy, it appears the allochems dissolved preferentially to the matrix/cement of the rocks and that some mechanical weathering happened as well. This work reports that the petrography and mineralogy of carbonate rocks is important to consider when exploring the cave, karst, and landscape evolution and that attention should be paid to the petrography of carbonate rocks when considering the global carbon budget.
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Cai, Jin Hang. "The Accumulation Rules of Budate Burial Hill Hydrocarbon Reservoir of Suderte Oilfield in Hailar Basin." Applied Mechanics and Materials 733 (February 2015): 140–43. http://dx.doi.org/10.4028/www.scientific.net/amm.733.140.
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Metamorphic rock burial hill reservoir of Beier rift in Hailaer Basin, with large scale reservoir and high output has complex fault system. The fault through going direction roughly is NEE direction, and has wide fault section and lateral quickly changed fault displacement. Metamorphic rock reservoir can be divided into the vertical weathered fracture zone, crack and dissolved pores and caves development belt and tight zone. Accumulation is controlled by hydrocarbon ability of source rock, contacting relationship of source rock and reservoir, oil storage ability of reservoir, and vertical and lateral hydrocarbon migration ability of fault and unconformity surface. And formed top surface weathering crust accumulation pattern which the hydrocarbon migrated laterally along the unconformity surface, and interior reservoir pattern of crack broken zone accumulation which hydrocarbon migrated vertically along fault.
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Négrel, Philippe, Anna Ladenberger, Clemens Reimann, Alecos Demetriades, Manfred Birke, and Martiya Sadeghi. "GEMAS: adaptation of weathering indices for European agricultural soil derived from carbonate parent materials." Geochemistry: Exploration, Environment, Analysis 22, no. 1 (December 2, 2021): geochem2021–059. http://dx.doi.org/10.1144/geochem2021-059.
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Carbonate rocks are very soluble and export elements in dissolved form, and precipitation of secondary phases can occur on a large scale. They leave a strong chemical signature in soil that can be quantified and classified by geochemical indices, and which is useful for evaluating chemical weathering trends (e.g. the Chemical Index of Alteration (CIA) or the Mafic Index of Alteration (MIA)). Due to contrasting chemical compositions and high Ca content, a special adaptation of classical weathering indices is necessary to interpret weathering trends in carbonate-derived soil. In fact, this adaptation seems to be a good tool for distinguishing weathering grades of source-rock types at the continental scale, and allows a more robust interpretation of soil parent-material weathering grade and its impact on the current chemical composition of soil. An increasing degree of weathering results in Al enrichment and Mg loss in addition to Fe loss and Si enrichment, leaching of mobile cations such as Ca and Na, and precipitation of Fe-oxides and hydroxides. The relation between soil weathering status and its spatial distribution in Europe provides important information about the role played by climate and terrain. The geographical distribution of soil chemistry contributes to a better understanding of soil nutritional status, element enrichment, degradation mechanisms, desertification, soil erosion and contamination.
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CHÁVEZ, WILLIAM X. "Supergene Oxidation of Copper Deposits: Zoning and Distribution of Copper Oxide Minerals." SEG Discovery, no. 41 (April 1, 2000): 1–21. http://dx.doi.org/10.5382/segnews.2000-41.fea.
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ABSTRACT Copper oxides represent an attractive exploration target because even low-grade prospects have the potential to produce low-cost copper in an environmentally friendly fashion. Derived from liypogene and/or supergene sulfides, copper oxides comprise a series of distinct assemblages that characterize a variable pH. oxidizing geochemical environment known as “the oxide zone.” Development of oxide copper minerals is a function of source-rock and host-rock mineralogy, pyrite and other (copper) sulfide abundance and distribution, fracture density and distribution, phreatic and/or vadose zone occurrence and stability, and maturity of the weathering profile The paragenesis оf copper oxide mineral formation reflects local, dynamic changes in supergene solution composition attributable to reaction between host-rock mineral components and dissolved species Especially important are the concentrations of because mineral assemblages, even those that are metastable. represent the geochemical environment in which they formed, identification and mapping of copper oxides is useful in interpreting the geochemical history of an oxide zone. Furthermore, practical application of oxide zone geochemistry is significant in the recognition and solution of problems associated with weathering-engendered metals oxidation and transport from mine wastes.
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Amann, Thorben, Jens Hartmann, Eric Struyf, Wagner de Oliveira Garcia, Elke K. Fischer, Ivan Janssens, Patrick Meire, and Jonas Schoelynck. "Enhanced Weathering and related element fluxes – a cropland mesocosm approach." Biogeosciences 17, no. 1 (January 8, 2020): 103–19. http://dx.doi.org/10.5194/bg-17-103-2020.
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Abstract. The weathering of silicates is a major control on atmospheric CO2 at geologic timescales. It was proposed to enhance this process to actively remove CO2 from the atmosphere. While there are some studies that propose and theoretically analyze the application of rock powder to agricultural land, results from field experiments are still scarce. In order to evaluate the efficiency and side effects of Enhanced Weathering (EW), a mesocosm experiment was set up and agricultural soil from Belgium was amended with olivine-bearing dunite ground to two different grain sizes, while distinguishing setups with and without crops. Based on measurements of Mg, Si, pH, and DIC, the additional weathering effect of olivine could be confirmed. Calculated weathering rates are up to 3 orders of magnitude lower than found in other studies. The calculated CO2 consumption by weathering based on the outlet water of the mesocosm systems was low with 2.3–4.9 tCO2km-2a-1 if compared with previous theoretical estimates. Suspected causes were the removal or dilution of Mg as a weathering product by processes like adsorption, mineralization, plant uptake, evapotranspiration, and/or preferential flow, not specifically addressed in previous EW experiments for CO2 consumption. The observation that Mg concentrations in the upper soil layers were about 1 order of magnitude higher than in the outlet water indicates that a careful tracking of weathering indicators like Mg in the field is essential for a precise estimate of the CO2 consumption potential of EW, specifically under global deployment scenarios with a high diversity of ecosystem settings. Porewater Mg∕Si molar ratios suggest that dissolved Si is reprecipitating, forming a cation-depleted Si layer on the reactive mineral surface of freshly ground rocks. The release of potentially harmful trace elements is an acknowledged side effect of EW. Primarily Ni and Cr are elevated in the soil solution, while Ni concentrations exceed the limits of drinking water quality. The use of olivine, rich in Ni and Cr, is not recommended, and alternative rock sources are suggested for the application.
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Colman, Steven M., and Kenneth L. Pierce. "Glacial Sequence Near McCall, Idaho: Weathering Rinds, Soil Development, Morphology, and Other Relative-Age Criteria." Quaternary Research 25, no. 1 (January 1986): 25–42. http://dx.doi.org/10.1016/0033-5894(86)90041-4.
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The sequence of glacial deposits near McCall, Idaho, previously assigned to the Pinedale and Bull Lake glaciations, contains deposits of four different ages. These ages are defined by multiple relative-age criteria, including weathering rinds, soil development, surface-rock weathering, morainal morphology, and loess stratigraphy. The thickness of weathering rinds on basaltic clasts is statistically representative and reproducible and can be used to estimate numerical ages. Following in order of decreasing relation to age are soil development, surface-rock weathering, and moraine morphology. The glacial deposits near McCall appear to correspond to times of high worldwide ice volume indicated by the marine oxygen-isotope record. Pilgrim Cove and McCall deposits, both assigned to the Pinedale glaciation, are late Wisconsin in age, perhaps 14,000 and 20,000 years, respectively. They represent a rare case in which deposits of Pinedale age can be separated by relative-age data. Timber Ridge deposits, assigned to the Bull Lake glaciation, have subdued, but well-preserved morainal morphology; relative-age data indicate that they are pre-Wisconsin in age, probably about 140,000–150,000 years old, although we cannot exclude an older age. Williams Creek deposits are clearly distinct from, and intermediate in age between, McCall and Timber Ridge deposits. Weathering rinds and the inferred ages of the other deposits suggest an early Wisconsin age for Williams Creek deposits.
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Xiao-Mei, Hui, Yuan Jin, Li Chao, Fan Xiao-Jun, and Zhou Yuan. "Analysis of hydrochemical characteristics and genesis of water-deficient rivers in China: a case study of the Ciyao River Basin in Shanxi Province." Quality Assurance and Safety of Crops & Foods 15, no. 1 (January 1, 2023): 32–43. http://dx.doi.org/10.15586/qas.v15i1.1213.
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In order to explore the chemical water characteristics of water-scarce rivers in China, the Ciyao River basin in Shanxi Province was taken as a case study. Water samples of the mainstream and its tributaries were collected in the wet, normal, and dry seasons of 2021. The composition and spatial variation of the main ions in the water body were analyzed using the ion chromatography (IC) instrument. In addition, Pearson correlation analyses were used to evaluate relevant correlation between ion concentrations. The results showed that the overall surface water in the study area was weakly alkaline, and the content of total dissolved solids (TDS) varied greatly, ranging from 702 to 5091 mg/L, with an average of 2897 mg/L. The TDS showed a middle stream > downstream > upstream trend, and the hydrochemical type was Cl • SO4 • HCO3 – Ca • Na. The contents of most ions were significantly changed based on differences in sampling sites and seasons. Natural and human factors influence the chemical characteristics of the river. According to the Gibbs diagram and Piper diagram (Figure 3), the ionic composition of the water body in the basin is mainly affected by the joint action of rock weathering and evaporative crystallization. Carbonate rocks constitute the most significant rock weathering, followed by evaporative and silicate rocks. Wastewater from industrial enterprises, agricultural wastewater, and activities of people’s daily living also have some influence on rock weathering. Cation exchange is also important in forming chemical water components in the Ciyao River. The research results can provide technical references and a basis for regional water environment protection, water resources development and utilization, and watershed eco-hydrology research.
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Novikov, Dmitry A., Aleksandr N. Pyrayev, Fedor F. Dultsev, Anatoliy V. Chernykh, Anna F. Sukhorukova, Anton S. Derkachov, and Anastasia A. Maksimova. "ISTOPIC COMPOSITION (H, O AND C) OF NATURAL WATERS OF THE NOVOSIBIRSK CITY AGLOMERATION." Interexpo GEO-Siberia 2, no. 1 (May 21, 2021): 149–59. http://dx.doi.org/10.33764/2618-981x-2021-2-1-149-159.
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The paper presents the first data on the regional distribution of the isotopic composition of oxygen and hydrogen in waters, as well as the carbon of water-dissolved carbon dioxide in natural surface and underground infiltration waters of the Novosibirsk urban agglomeration. For the presented sample of samples, the vector of changes in the values of δD and δO in the studied region was obtained from -112 to -126 ‰ and from -14 to -16 ‰, respectively. The water-dissolved carbon dioxide of the studied waters has the expected biogenic genesis, the isotopic composition of carbon (δC from -14.0 to -7.0 ‰) indicates its participation in the processes of silicate-carbonate weathering.
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Zhang, Qianzhu, Ke Jin, Linyao Dong, Ruiyi Zhao, Wenxiang Liu, Yang Lu, Xiaoqing Gan, Yue Hu, and Cha Zhao. "The Hydrochemistry, Ionic Source, and Chemical Weathering of a Tributary in the Three Gorges Reservoir." Sustainability 14, no. 22 (November 18, 2022): 15376. http://dx.doi.org/10.3390/su142215376.
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Riverine dissolved matter reflects geochemical genesis information, which is vital to understand and manage the water environment in a basin. The Ganjing River located in the hinterland of the Three Gorges Reservoir was systematically investigated to analyze the composition and spatial variation of riverine ions, probe the source and influencing factors, and assess the chemical weathering rates and CO2 consumption. The results showed that the total dissolved solid value (473.31 ± 154.87 mg/L) with the type of “HCO3−–Ca2+” was higher than that of the global rivers’ average. The hydrochemical parameters were relatively stable in the lower reservoir area of the Ganjing River, which was largely influenced by the backwater of Three Gorges Reservoir. The carbonate weathering source contributed 69.63% of TDS (Total dissolved solids), which generally dominated the hydrochemical characteristics. The contribution rates of atmospheric rainfall were relatively low and stable in the basin, with an average of 4.01 ± 1.28%. The average contribution rate of anthropogenic activities was 12.05% in the basin and even up to 27.80% in the lower reservoir area of the Ganjing River, which illustrated that the impoundment of Three Gorges Reservoir had brought great challenges to the water environment in the reservoir bay. The empirical power functions were tentatively proposed to eliminate the dilution effect caused by runoff discharge on the basis of previous studies. Accordingly, the rock weathering rate was calculated as 23.54 t/km2 in the Ganjing River Basin, which consumed atmospheric CO2 with a flux of 6.88 × 105 mol/y/km2. These results highlight the geochemical information of tributaries in the hinterland of the Three Gorges Reservoir, have significant implications for understanding the impact of impoundment, and provide data support for the integrated management of water resources in the Ganjing River Basin.
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Marchina, C., C. Natali, M. F. Fahnestock, M. Pennisi, J. Bryce, and G. Bianchini. "Strontium isotopic composition of the Po river dissolved load: Insights into rock weathering in Northern Italy." Applied Geochemistry 97 (October 2018): 187–96. http://dx.doi.org/10.1016/j.apgeochem.2018.08.024.
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Mordberg, L. E., C. J. Stanley, and A. V. Antonov. "Polystage apatite recrystallization and svanbergite formation during weathering in an acid karstic environment." Mineralogical Magazine 72, no. 1 (February 2008): 95–99. http://dx.doi.org/10.1180/minmag.2008.072.1.95.
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AbstractA Devonian weathering profile was developed near the contact of Riphean dolostone containing disseminated carbonate-fluorapatite and intensively pyritized black shales. Samples from the profile were investigated by XRF, SEM, electron microprobe and ion microprobe. Rock-forming minerals are apatite, diaspore, chlorite and kaolinite, while accessory minerals are svanbergite, anatase, pyrite and zircon.Primary marine carbonate-fluorapatite is represented by extremely weathered crystals concentrated near the footwall. Dissolution of apatite and pyrite provided an acidic environment that is expressed in the formation of S-rich apatite and svanbergite. The environment allowed Ti migration which formed anatase in weathered apatite grains. Coupled substitution Na+ + S6+ = Ca2+ + P5+ is suggested in S-rich apatite. A large volume of dissolved carbonate rocks was a source of Sr necessary for svanbergite formation. Apatite of the third generation formed at the final stage of weathering is represented by small (10—30 μm) very well shaped crystals.
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Kou, Li, Hua, and Li. "Hydrochemical Characteristics, Controlling Factors, and Solute Sources of Streamflow and Groundwater in the Hei River Catchment, China." Water 11, no. 11 (November 1, 2019): 2293. http://dx.doi.org/10.3390/w11112293.
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Water scarcity in arid regions is exacerbated by water quality degradation from anthropogenic contamination. In water-scarce regions, it is crucial to identify hydrochemical characteristics and pollution sources for effective water resource management. In this study, the Hei River—located in the Loess Plateau of China, which is an arid region with substantial anthropogenic-induced environmental changes—was selected as the study area to investigate these issues. The major ions of 242 streamflow and groundwater samples were measured during the 2014 and 2015 dry and flood seasons. Using a Piper diagram, a fuzzy membership function, a Gibbs diagram, and a forward model, the hydrochemical facies and water quality of streamflow and groundwater were investigated, and the main river solute sources and relative contributions were determined using quantitative and qualitative methods. The total dissolved solids were 279.6 ± 127.8 mg·L−1 for streamflow and 354.0 ± 157.4 mg·L−1 for groundwater, indicating low salinity water. However, the hydrochemical characteristics varied with season and location. Qualitatively, the atmospheric inputs, human activities, and rock weathering all contributed solutes to the waters but with varying contributions. The following are the mean contributions of analyzed solute source: silicate weathering (45.1 ± 1.1%) > carbonate weathering (34.1 ± 1.6%) > evaporite dissolution (13.7 ± 2.4%) > atmospheric input (5.4 ± 0.1%) > anthropogenic input (1.7 ± 0.1%). In general, water quality was satisfactory, as the majority of samples conformed to drinking water standards. The samples had good water quality because the river solutes were not heavily affected by anthropogenic activities and were primarily controlled by rock weathering. However, localized areas of high anthropogenic impact were identified. Such locations should be prioritized for pollution control and water resource management.
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Rosa, Eric, Jérôme Gaillardet, Claude Hillaire-Marcel, Jean-François Hélie, and Louis-Filip Richard. "Rock denudation rates and organic carbon exports along a latitudinal gradient in the Hudson, James, and Ungava bays watershed." Canadian Journal of Earth Sciences 49, no. 6 (June 2012): 742–57. http://dx.doi.org/10.1139/e2012-021.
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This study documents chemical denudation rates (CDR) in the Canadian Shield and Interior Platform. It focuses on the dissolved chemistry of rivers flowing into the Hudson, James, and Ungava bays (HJUB). Major ions, strontium, neodymium, and dissolved organic carbon (DOC) concentrations were monitored in four rivers (Koksoak, Great Whale, La Grande, and Nelson). Six other rivers flowing into the HJUB were sampled during baseflow and snowmelt conditions. The rivers of the Canadian Shield exhibit major cation concentrations ranging between 62 and 360 µmol/L, [Nd] of 0.57–4.72 nmol/L, and variable [DOC] of 241–1777 µmol/L. In comparison, the Nelson River (Interior Platform) shows higher major cation concentrations (1200–2276 µmol/L), lower [Nd] (0.14–0.45 nmol/L), and intermediate [DOC] (753–928 µmol/L). Altogether, the studied rivers export 8 × 106 t/year of dissolved major cations and 50 t/year of dissolved Nd towards the HJUB. Basin-scale rock denudation rates (RDR) range from 1.0 to 5.3 t·km–2·year–1 and are essentially controlled by lithology, as illustrated by the relationship established between RDR and the proportion of sedimentary and volcanic rocks (%S + %V) within the basins: RDR = 0.08(%S + %V) + 0.9. In contrast, dissolved Nd exports (and likely other insoluble elements) seem to be dependent upon organic matter leaching, as illustrated by the empirical coupling between Nd and DOC exports. These fluxes decrease northwards, likely in response to the hydroclimatic gradient. The CDR evaluated within the Canadian Shield are among the lowest on the planet, and the alkalinity generated by rock weathering remains small with respect to DOC exports.
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Bedoya-Gonzalez, Diego, Sylke Hilberg, Günther Redhammer, and Thomas Rinder. "A Petrographic Investigation of the Carboniferous Sequence from the Ibbenbüren Mine: Tracing the Origin of the Coal Mine Drainage." Minerals 11, no. 5 (April 30, 2021): 483. http://dx.doi.org/10.3390/min11050483.
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The mine drainage of the Ibbenbüren anthracite coal mine is characterized by exceptionally high concentrations of dissolved iron and sulfate. The elevated position of the coal field with respect to the surrounding area makes the neighboring sediments an unlikely source of these elements. Accordingly, it has been hypothesized that interaction between infiltrating rainwater and the fractured overburden is a key process governing the mine drainage chemistry. To test this hypothesis, two full-diameter core samples drilled above the discharging adit of the coal mine were investigated. The methodology combined several analytical techniques to identify and characterize traces of water–rock interaction related to both diagenesis and relatively recent weathering processes along open fractures. The coupled appearance of kaolinite-dickite-illite minerals in weathered and unweathered rock sections was clearly connected to the burial history of the Carboniferous sequence. In contrast, the formation of iron (oxide-) hydroxides together with the presence of oxidized pyrite in weathering profiles along both sides of the fractures was positively related to the geochemical footprint of the coal mine drainage. Thus, open fractures, possibly originated from mining activities, may play a significant role in the drainage chemistry, especially considering the rather poor hydraulic conditions of the overburden.
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Khan, M. Shamim, A. H. M. Ahmad, and R. Agarwal. "Petro-chemistry and diagenesis of sandstones of Patherwa Formation, Son Valley, India." Journal of Palaeosciences 63, no. (1-2) (December 31, 2014): 25–32. http://dx.doi.org/10.54991/jop.2014.318.
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The sandstone of Patherwa Formation, (Semri Group) is constituted by quartz, feldspar, micas, rock fragments and heavy minerals. Abrupt changes in the grain size are recorded and sandstone is grouped as fine–grained (FGS), medium–grained (MGS), coarse–grained (CGS) and very coarse–grained (VCGS). The field and petrographic divisions are equally reflected in their chemistry. CGS shows highest SiO2 content (mean 86.59 wt%) followed by MGS (mean 80.78 wt%), VCGS (mean 76.51 wt%) and FGS (mean 75.21 wt%). SREE content is highest in FGS (180.51 ppm) and lowest in CGS (129.64 ppm). VCGS possesses anomalously high SREE values (2070.62 ppm). Range of weathering indices including CIA, CIW, PIA and ICV indicates moderate to strong chemical weathering in the provenance. Large range of variation in weathering indices suggests that physical weathering facilitated chemical weathering, under subtropical humid climate. Mechanical compaction led the rearrangement of grains forming point and long contacts while diagenesis dissolved mobile grains which made sandstone highly quartzose. The progressive compaction getting initiated at the sediment–water interface continued till deep burial in a rapidly subsiding basin. Geochemical provenance modelling suggests production of detritus from a predominately granite–gneissic terrain bearing some mafic rocks. Palaeocurrent data indicates sediment supply from two source terrains, i.e. BGC and Bijawar. Synthesis of petrochemical attributes and diagenesis history, assigns a tectonically active setting where generation of positive relief and its desecration was taking place in quick tandem. The most likely such setting is tectonic uplift due to continental collision.
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Herczeg, A. L., S. S. Dogramaci, and F. W. J. Leaney. "Origin of dissolved salts in a large, semi-arid groundwater system: Murray Basin, Australia." Marine and Freshwater Research 52, no. 1 (2001): 41. http://dx.doi.org/10.1071/mf00040.
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Hypotheses to explain the source of the 1011 tons of salt in groundwaters of the Murray Basin, south-eastern Australia, are evaluated; these are (a) mixing with original sea water, (b) dissolution of salt deposits, (c) weathering of aquifer minerals and (d) acquisition of solutes via rainfall. The total salinity and chemistry of many groundwater samples are similar to sea-water composition. However, their stable isotopic compositions (δ18O= –6.5 ‰; δ2H = –35) are typical of mean winter rainfall, indicating that all the original sea water has been flushed out of the aquifer. Br/Cl mass ratios are approximately the same as sea water (3.57 x 10-3) indicating that NaCl evaporites (which have Br/Cl<10-4) are not a significant contributor to Cl in the groundwater. Similarly, very low abundances of Cl in aquifer minerals preclude rock weathering as a significant source of Cl. About 1.5 million tons of new salt is deposited in the Murray–Darling Basin each year by rainfall.The groundwater chemistry has evolved by a combination of atmospheric fallout of marine and continentally derived solutes and removal of water by evapo-transpiration over tens of thousands of years of relative aridity. Carbonate dissolution/precipitation, cation exchange and reconstitution of secondary clay minerals in the aquifers results in a groundwater chemistry that retains a ‘sea-water-like’ character.
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Kumar, Ajay, R. M. Tripathi, Sabyasachi Rout, Manish K. Mishra, P. M. Ravi, and A. K. Ghosh. "Characterization of groundwater composition in Punjab state with special emphasis on uranium content, speciation and mobility." Radiochimica Acta 102, no. 3 (February 10, 2014): 239–54. http://dx.doi.org/10.1515/ract-2014-2109.
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Abstract Groundwaters (borewell and handpump) were sampled from two districts (Bathinda and Mansa) of Punjab state and analyzed for their major ionic concentrations and uranium isotope compositions in order to assess the possible origins of the waters and water–rock interactions that occurred in the deep aquifer system. The major ionic concentrations of waters were plotted on a Piper diagram and grouped into four dominant hydrochemical facies as (Na+K)-SO4+Cl type (69% – 73%), (Ca+Mg)-SO4+Cl type (6% – 21%), (Ca+Mg)–HCO3 type (4% – 6%) and (Na+K)-HCO3 type (2% – 19%). It was observed that mobility of uranium in groundwater was very much influenced by TDS (total dissolved solids). To investigate the various mechanisms for deriving the elevated uranium concentrations in groundwater, 234U/238U activity ratios (ARs) were calculated using the determined activity levels of 234U and 238U. The mean ARs was found to be near unity (i.e. secular equilibrium) in the study regions confirmed that uranium in groundwaters was mainly resulted from its host/parent rocks through weathering processes. The concentration of HCO3 − in ground water showed one order of magnitude higher than the total dissolved SiO2 indicates that carbonate weathering was the dominant process due to major water–rock interaction. The uranium speciation in groundwaters was investigated by an equilibrium model calculation using MEDUSA (make equilibrium diagrams using sophisticated algorithms) under the influence of redox conditions and complexant concentration. At the observed range of pH values, the predominant redox speciation of uranium was observed as hydroxo-carbonato complexes of (UO2)2(CO3)(OH)3 − and hydroxyl complexes of UO2(OH)3 − which might be caused for increasing the solubility of uranium. Due to very low concentration of phosphate in groundwater, its effects on U(VI)-aqueous speciation was negligible.
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Day, Stephen J. "Small-scale field evaluation of geochemical blending of waste rock to mitigate acid rock drainage potential." Geochemistry: Exploration, Environment, Analysis 22, no. 1 (November 29, 2021): geochem2021–066. http://dx.doi.org/10.1144/geochem2021-066.
Full textAbstract:
Blending of potentially acid generating (PAG) waste rock with non-PAG waste rock to create a rock mixture which performs as non-PAG is a possible approach to permanent prevention of acid rock drainage (ARD) for PAG waste rock. In 2012, a field weathering study using 300 kg samples was implemented at Teck Coal's Quintette Project located in northeastern British Columbia, Canada to test the prevention of acid generation in the PAG waste rock by dissolved carbonate leached from overlying non-PAG waste rock and direct neutralization of acidic water from PAG waste rock by contact with non-PAG waste rock.After eight years of monitoring the experiments, the layered non-PAG on PAG barrels provided proof-of-concept that as the thickness of the PAG layer increases relative to the thickness of the non-PAG layers, acidic waters are more likely to be produced. The PAG on non-PAG layering has resulted in non-acidic water and no indications of metal leaching despite accelerated oxidation in the PAG layer shown by sulfate loadings. The study has demonstrated that the scale of heterogeneity of PAG and non-PAG materials is a critical consideration for providing certainty that rock blends designed to be non-PAG will perform as non-PAG in perpetuity. This is contrary to the standard paradigm in which an excess of acid-consuming minerals is often considered sufficient alone to ensure ARD is not produced.
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Oyama, T., Y. Inohara, and T. Nagaoka. "In situ investigation of the redox front above an underground rock cavern and estimation of its moving rate." Mineralogical Magazine 72, no. 1 (February 2008): 107–9. http://dx.doi.org/10.1180/minmag.2008.072.1.107.
Full textAbstract:
AbstractAn investigation and evaluation of the redox conditions around an underground rock cavern are important from the viewpoint of the safety assessment of the subsurface geological disposal of radioactive wastes. The in situ redox conditions around a cavern excavated in Neogene pyroclastic rocks were investigated. Rock samples were collected from a tunnel wall crossing the oxidation front, and the properties of pore water seeping into small holes drilled in the tunnel wall were determined. Chemical analysis of the rock samples revealed that pyrite-bearing rocks belowthe oxidation front were oxidized by the dissolved oxygen in the groundwater infiltrating from the surface. The water properties changed with increasing oxidation of the rocks. From the amount of oxygen-consuming components in the rocks, the migration rate of the oxidation front was estimated to be ~0.2 mm/y due to the flowrate of groundwater (0.1 m/y) containing oxygen.