Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 19 of 19 for “"silicate weathering"”.
-
Silicate weathering in the Himalayas: Constraints from the Li isotopic composition of river systems
Chemical weathering of silicate rock consumes atmospheric CO2 and supplies the oceans with cations, thereby controlling both seawater chemistry and climate. The rate of CO2 consumption is closely linked to the rate of CO2 outgassing from the planetary interior, providing a negative feedback loop …
-
Adsorption–Desorption Reactions in the Weathering Zone: Implications for Silicate Weathering & the Carbon Cycle
The carbonic acid-driven chemical weathering of silicate minerals removes carbon dioxide (CO2) from Earth's atmosphere. The tectonic processes of uplift, exhumation, and erosion modulate the negative feedback relationship between climate, silicate weathering rates, and atmospheric CO2 removal rates …
-
A spatial and temporal study of the carbon cycle; the role of carbonates in buffering Earth’s climate
… imbalance between volcanic degassing rates and silicate weathering. To force environmental changes in this way, such as the CO<sub>2</sub> decline observed during the Cenozoic Period (66 Myr - present), requires either a decrease in volcanic degassing, or an increase in silicate weathering and a …
-
Sediment chemistry as an archive of provenance and weathering in the Mekong River Basin
The chemical weathering of rocks, in particular silicate weathering, has been proposed to be an important natural carbon-removal process that regulates the Earth’s climate over millions of years. Tectonically active regions, such as the sub-Himalayan region, are considered a hotspot of silicate …
-
Geochemical Investigations of Mineral Weathering: Quantifying Weathering Intensity, Silicate versus Carbonate Contributions, and Soil-Plant Interactions
… study is the geochemical examination of mineral weathering and its path from hinterland, through sediment deposition and pedogenesis, to its dissolution and eventual uptake into plants or precipitation as carbonate minerals. The three papers examine the rate and character of carbonate and …
-
Four problems in nonlinear Earth system dynamics
… stabilizing feedbacks. One example is the silicate weathering feedback, which is often invoked to explain recovery from large Earth system disruptions, and Earth’s persistent habitability thus far. I show that stabilizing feedbacks indeed controlled temperature on timescales of thousands to …
-
The Formation and Evolution of Habitable Worlds
… Chapter 5, from a coupled climate and carbonate-silicate weathering model, we show that similarly broad ranges for atmospheric CO2 are expected on Earth-like planets in the HZ. Despite this predicted spread in atmospheric CO2 in the HZ, we show a relationship between CO2 and incident flux should …
-
Reconstruction of the Late and Mid-Pleistocene climate and landscape history in SE-Central Europe - A paleopedological and geochemical multi-proxy approach in loess-paleosol studies.
… proxies especially geochemically based weathering indices, as well as biomarker and stable isotope approaches in LPSS research. The results from geochemical analyses reveal that alluvial material of the Danube and its tributaries represent major sources for the loess in the middle and …
-
The Evolution and Impact of Weddell Sea Deep Water
… and identification of marine forward and reverse silicate weathering processes (dissolved stable Si and radiogenic Sr isotopes, fine grained K’/Ar ages). Overall, the novel findings of this dissertation demonstrate that the coupling between the Antarctic Ice Sheet and Southern Ocean circulation is …
-
Basalt Weathering And Carbon Sequestration In Willamette Valley Hazelnut Orchards With Restoration Site Applications
… applied through a process called enhanced rock weathering (ERW), could serve as a uniquely viable and climate positive alternative to agricultural lime in Oregon's Willamette Valley hazelnut orchards. Oregon produces 99% of the United States' hazelnuts, and maintaining hazelnut productivity …
-
Assessment of groundwater quality in a part of Mhlathuze catchment of Empangeni and Richards Bay, KwaZulu-Natal, South Africa
… and reverse ion exchange, carbonate and silicate weathering processes and evaporation. PI values specified that the quality of groundwater is good for irrigation purposes. The abundance of metals exhibited the sequence in increasing order as follows: Mn < Si < Fe < B < Cu < Zn < Pb < Al < …
-
RE – OS AND PGE GEOCHEMISTRY OF ORGANIC-RICH SEDIMENTARY ROCKS AND PETROLEUM
… 0.28 – 1.08, providing evidence for increased silicate weathering of radiogenic continental crust. A decrease to less radiogenic Osi (~0.60) occurs at the base Hirnantian and marks the onset of the Hirnantian Glaciation. This is ascribed to Hirnantian ice cover and reduced chemical weathering …
-
The hydrochemical and isotopic characterization of groundwater in southern Mozambique
… had an NA/Cl ration greater than one, indicating silicate weathering as a major process affecting the chemical character of the water. Samples in the basalts however had Na/Cl ratios less than one, and δ 2H and δ 18O values out of the range of seawater, suggesting ion exchange as a process …
-
Ultramafic Alteration and the Cooling of Earth and Mars
… organic carbon. I use a combination of mineral weathering models and proxy data to show that this mechanism has contributed to the glaciations of the Palaeozoic (541 - 252 Ma). Unlike Earth, igneous rocks on the Martian surface are frequently of ultramafic composition. My second chapter argues …
-
Hydrogeochemical evaluation and groundwater quality assessment for drinking and irrigation purposes in Bushbuckridge, South Africa.
… Na-HCO3, Ca-HCO3 and Mg-Ca-HCO3 mixed type. Rock weathering was the dominant geochemical process, associated with evaporation. Water-rock interactions through silicate weathering and ion exchange reactions between Ca2+, Mg2+ and Na+ were determining factors influencing the hydrochemical evolution …
-
Middle Miocene carbon cycle dynamics: A multi-proxy approach
… records presented here, the recently suggested “silicate weathering hypothesis” (Shevenell et al., 2008) for CM6 is untenable. The mechanism preferred here is increased organic carbon burial, in agreement with the “Monterey Hypothesis”. <br></br><br></br> Coupled inorganic-organic carbon isotopes …
-
Assessment of coastal aquifer contamination using geochemical and health risk assessment in Maputaland formations, South Africa
… revealed that ion exchange, reverseion exchange, silicate weathering, seawater mixing, and anthropogenic inputs from agricultural activities govern the groundwater chemistry. GIS methods were adopted to produce spatial distribution maps of major ions through which locations of groundwater …
-
A modeling framework for characterizing root exudation-driven geochemical dynamics in the Critical Zone
… that such root processes promote soil weathering, there are no existing models capable of describing the interaction of root exudation with temporally-variable processes ranging from mineral dissolution to energy and moisture fluxes in the soil column in a single framework. The goal of …
-
Weathering below Irish blanket bogs and impacts on carbon dynamics
… investigates CO2 consumption by chemical weathering related to mineral soils and bedrock underlying peatland catchments in Ireland via measurement of major ion fluxes and runoff. Influence of peatland condition and substrate composition is investigated by comparison of catchments with …