Geochemistry of Colloid Systems for Earth Scientists

Yariv, S.; Cross, Harold

doi:10.1097/00010694-198007000-00011

Cited by 30 publications

(12 citation statements)

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“…For constant-charge clay surfaces, the surface conductivity may be roughly estimated by Equation 4. Clay minerals (except zeolites, Yariv and Cross, 1979;Olhoeft, 1981;Talibudeen, 1981) have surfaces with constant charges (and therefore are of constant CEC). In the absence of significant pore-volume deformation as a result of a temperature increase, the temperature dependence of the surface conductivity is attributable to the counter-ion mobility, ß.…”

Section: Formation Factor and Surface Conductivitymentioning

confidence: 99%

Electrical Conduction in Oceanic Dikes, Hole 504B

Revil¹,

Darot²,

Pézard³

et al. 1996

Proceedings of the Ocean Drilling Program, 148 Scientific Results

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Porosity, cation-exchange capacity (CEC), and electrical conductivity have been measured on 28 doleritic minicores from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) Hole 504B (Legs 137, 140, and 148). Conductivity experiments were performed under five different saturating-fluid salinities, at room temperature and pressure, and with a twoelectrode conducting cell. At 4 kHz, the porosity is related to the "intrinsic" formation factor by an inverse power law similar to Archie's formula F = a Φ" m with m = 0.94 and a = 16 for the fine-grained specimens. Such a low m value suggests a current conduction in cracks and microcracks present at mineral scale throughout the rock. The presence of clays as alteration products is reflected by the high values of CEC. As expected, Q v /F (where Q v is the CEC per unit pore volume) and the surface conductivity are well correlated. This point leads to an estimate of the surface tortuosity. The temperature dependence of the surface conductivity is extracted using data on DC electrical conductivity at different temperature. For temperature correction purposes, a linear temperature dependence appears to be a good estimate for this parameter.On the basis of these results, an equation was given that allows estimation of the porosity from resistivity measurements in Hole 504B. This equation was tested by comparing the predicted conductivity against the measured conductivity of a large set of samples.

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Section: Formation Factor and Surface Conductivitymentioning

confidence: 99%

Electrical Conduction in Oceanic Dikes, Hole 504B

Revil¹,

Darot²,

Pézard³

et al. 1996

Proceedings of the Ocean Drilling Program, 148 Scientific Results

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“…Para Yariv & Cross (1979), a dissolução da sílica depende das propriedades da solução tais como: o estado no qual a sílica se encontra (grau de cristalização ou fase amorfa), pH, tempo das reações químicas; temperatura; presença de vários sais, e compostos orgânicos e inorgânicos. Szcerban e Urbani (1974) ressaltam que a resistência da sílica ao intemperismo químico é bastante variável.…”

Section: Dissolução Das Rochas Siliciclásticasunclassified

Relevo Cárstico Em Rochas Siliciclásticas: Uma Revisão Com Base Na Literatura

Fabri

Auler

Augustin³

2014

Rev. Bras. Geomorfol.

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Resumo:O relevo cárstico foi durante muito tempo associado à presença de rochas carbonáticas, em função da predisposição das mesmas à atuação dos processos de dissolução. Estudos recentes vêm mostrando, no entanto, que feições semelhantes àquelas desenvolvidas nessas litologias estão também presentes em outros tipos de substrato rochoso, em especial nas siliciclásticas, desde que haja condições para que a dissolução e a retirada do material ocorram. Essas feições são consideradas como cársticas, uma vez que os processos de dissolução exercem papel fundamental no desenvolvimento das mesmas. Esta interpretação não constitui consenso entre os estudiosos, pois para alguns, essas feições não são resultantes predominantemente da dissolução, pois é baixa a solubilidade do quartzo. No Brasil, este tipo de rocha cobre grandes extensões territoriais, o que torna o entendimento dos fatores envolvidos na sua elaboração, bem como dos seus mecanismos associados, muito importantes para conhecer e compreender a evolução do relevo destas vastas áreas. Por se tratar de tema relativamente novo, sua discussão possibilita a difusão, e amplia o escopo desses estudos. O artigo busca contribuir para esse objetivo, ao apresentar com base na literatura, os principais aspectos conceituais e analíticos sobre o tema, com ênfase nas cavernas em rochas siliciclásticas. Informações sobre o Artigo Palavras-chave:Formas cársticas, rochas siliciclásticas, revisão da literatura.

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“…The impact of these geochemical processes relative to contaminant transport below the single-shell tank (SST) WMAs is discussed in the main body of this data package. Further background information regarding these geochemical processes is given by , , , Garrels and Christ (1965), Langmuir (1997), Lindsay (1979), Morel (1983, Nordstrom and Munoz (1985), Sposito ( , 1994, , Yariv and Cross (1979), and others, and the references cited therein.…”

Section: A1 Purposementioning

confidence: 99%

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

Cantrell¹,

Zachara²,

Dresel³

et al. 2007

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Companion reports that review other subject matter areas relevant to contaminant transport within the vadose zone beneath the SST WMAs, the IDF, and groundwater have been recently published. The specific subject areas include the geology of the SST WMAs iv contaminants released to the vadose zone exhibit a wide range of mobility behaviors. Many tank waste contaminants have been strongly retarded by adsorption and precipitation reactions (e.g., cesium, plutonium, americium, and europium), while others have remained mobile (e.g., technetium, nitrate, and selenium). Still others show variable, waste-specific behaviors (e.g., cesium [where sodium concentrations are very high], strontium, chromium, and uranium) that are closely tied to evolving composition of pore water in the sediments, and for chromium, a change in oxidation state. The temperature of in-ground tank waste has moderated by heat exchange with the subsurface sediment, and high concentrations of base (OH -) have been neutralized through reactions with sediment minerals and secondary mineral precipitation. Major geochemical features that may potentially affect the mobility of key contaminants of interest in the vadose zone include oxidation state, aqueous speciation, solubility, and adsorption reactions.Processes suspected of facilitating the far-field migration of immobile radionuclides, such as formation of stable aqueous complex formation and mobile colloids, were found to be potentially operative, but unlikely to occur in the field. An exception is the enhanced migration of cobalt-60 facilitated by the formation of highly stable aqueous-cyanide complexes. Certain fission-product oxyanions (e. • Adsorption is suppressed by large concentrations of tank waste anions (e.g., NO 3 -, OH -, and CO 3 2-)• Surface charge of clay-size minerals is negative and will therefore tend to repel anions• Unlike chromium, their less-soluble, less-mobile reduced forms are unstable in oxidizing environments.Laboratory studies conducted through PNNL's Vadose Zone Characterization Project and basic-science geochemical studies are expected to continue in partnership to provide information to further refine the conceptual model used for risk assessment modeling. Results of these studies can be used to help ascertain uncertainties associated with the refinement of the conceptual models for contaminant migration in the vadose zone beneath the single-shell tanks. Results can also provide improved parameterization, such as distribution coefficients (K d ), and mathematical constructs used by modelers to predict contaminant mobility under these conditions, and to decrease the degree of conservatism incorporated in these models.For various reasons, risk assessment models typically use various approximations to represent the conceptual model developed for the site. Adsorption is frequently approximated using empirical distribution coefficients (K d s). Although the use of empirical distribution coefficients can potentially lead to erroneous results under certain conditions where the...

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Geochemistry of Colloid Systems for Earth Scientists

Cited by 30 publications

References 0 publications

Electrical Conduction in Oceanic Dikes, Hole 504B

Electrical Conduction in Oceanic Dikes, Hole 504B

Relevo Cárstico Em Rochas Siliciclásticas: Uma Revisão Com Base Na Literatura

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

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