Rich Clay Research Articles

Calcined iron rich clay as an adsorbent and a photocatalyst for the degradation of phenol

This study investigates the potential of a calcined iron rich clay for the removal of phenol from aqueous solutions (adsorption) and subsequent degradation of the adsorbed phenol (photocatalysis). The calcined clay contains 21.47 % wt of α-Fe2O3which is a well known visible light responsive photocatalyst. Adsorption data were analyzed using the Langmuir and Freundlich isotherm models, as well as the pseudo-first-order and pseudo-second-order kinetic models. Adsorption of phenol on the calcined iron rich clay is best described by the Pseudo-secoond-order kinetic model and the Langmuir isotherm model. The adsorption capacity of the calcined iron rich clay for phenol was found to be higher than the reported capacity of bentonitic clay. Photocatalytic degradation of phenol using the calcined clay obeys pseudo-first order kinetic model. The apparent rate constants (kapp) of the photocatalytic degradation of phenol using the calcined iron rich clay are higher than the reported kapp for the photocatalytic degradation of phenol using TiO2. The calcined iron rich clay can be used to treat phenol containing wastewater via adsorption and photocatalysis.Key words: Adsorbent, Photocatalyst, Phenol, Calcined iron rich clay, Degradation

Laboratory study of the long-term durability of buried concrete exposed to Lower Lias Clay

This paper describes a long-term investigation into chemical degradation vulnerability of four different types of concrete that were exposed to pyrite rich clay. In this, four 100mm square by 1.2m long concrete columns made from Portland cement (PC), Portland limestone cement (PLC), sulfate resisting Portland cement (SRPC) and Portland cement blended with 25% pulverised fuel ash (PC–PFA) were buried for 9years in slightly weathered Lower Lias Clay of water soluble sulfate class DS-2. One face of each concrete column was coated with bitumen to test the performance of this method of protection. The temperature was controlled at 4.5±0.5°C using a cold water circulation system. The performance of the different concretes was assessed by means of visual observation supported by X-ray diffraction (XRD), Infra-red Scanning (IR) and Scanning Electron Microscopy with Energy Dispersive X-ray analysis (SEM-EDX) to identify the deterioration products.It was found that deterioration due to the thaumasite form of sulfate attack occurred in all four concretes with PLC concrete being the worst affected. The thickness of thaumasite deterioration into the concretes over the 9-year exposure was as follows: PLC=47; PC=33; SRPC=22 and PC–PFA=10mm. The study affirmed the susceptibility to Thaumasite Sulfate Attack (TSA) of both PC–25% PFA replacement and SRPC concretes. It was also found that, the amount of concrete deterioration decreased with increasing burial depth, which was probably due to reduced access to air. The bitumen coating, even if damaged, was an effective barrier at preventing deterioration in all concretes.

Functional megadiversity

Western Amazonian and Andean forests have Earth’s highest biodiversity and are globally important for ecosystem services and climate regulation. Straddling the planet’s longest ecological gradients, they have captured the imagination of scientists since von Humboldt (1). However, ecological studies and theory have incorporated that spectacular biological variation in only the most rudimentary ways, or not at all. It is widely understood that there are many traits that are important to plant performance, consequential not only for things like carbon gain and loss, but also timing of life histories, evolutionary patterns, and interactions with symbionts. In PNAS, Asner et al. (2) focus on one of the best known suites of traits, those comprising the biochemical functions of canopy leaves, on a breathtaking number of species drawn from nearly all major angiosperm clades. The study crosses ecological gradients spanning lowland Amazonian soil fertilities from poor white sands to rich clays, and an altitudinal gradient stretching 3.5 km from the hot lowlands to the frost and ice near the limit of tree growth in the Andes. The authors’ findings show that there is immense variability in functional traits found in the canopies of tropical forests: indeed, as much variability in the forests of western South America as was previously known for all tropical forests on the planet.

Shallow geological environment of Krishna–Godavari offshore, eastern continental margin of India as inferred from the interpretation of high resolution sparker data

Krishna–Godavari offshore basin, a part of the eastern continental margin of India is a proven petroliferous basin. Recent drilling in this area in search of gas hydrates reveals that the upper ∼300 m thick Quaternary–Recent strata comprised of nannofossil bearing rich clays and, fractures/faults are the suitable zones for gas hydrates accumulation. Therefore, the knowledge about the shallow geological environments and its architecture are significantly important in assessing the gas hydrates potential of this area. In order to enhance the geological understanding, the newly acquired high resolution seismic (HRS) reflection data in this gas hydrates prone area is interpreted. The processed seismic sections show a maximum penetration of 562 ms TWT (∼450 m) underneath the seabed with high resolution stratification. An attempt has been made to: (i) deduce the shallow geological environment from the reflection characteristics, and, (ii) assign tentative ages under the constraints of drilling/coring results. We further explained the observed folded structures on the surface and subsurface through a mechanism linked to shale tectonism and neotectonic activity.

Hydraulic properties of smectite rich clay controlled by hydraulic gradients and filter types

The common practice in geotechnical laboratories is to apply high hydraulic gradients for getting results in reasonable time but this can jeopardize the accuracy. In this paper, the hydraulic conductivity of a smectite rich clay from Iraq was determined under different hydraulic gradients (5 to 10,000m/m) using several densities and two permeants. Also, two types of filters were used, ordinary stainless steel sintered filter and sand/silt filter, in order to examine the possible effect of clogging by dragged clay gel particles. It was concluded that the outflow filter can affect the evaluated conductivity especially when applying high hydraulic gradients. For sintered filters the hydraulic conductivity was reduced as the gradient increased, while the conductivity increased as the hydraulic gradient increased when using sand/silt filters. For salt water the impact of the gradient was less obvious than for distilled water. A theoretical model was derived for selecting safe hydraulic gradients as a function of dry density, swelling pressure and permeant type. A major conclusion was that the gradient in laboratory testing should not exceed 100m/m.

Palaeoenvironmental and chronological constraints on the Tuğlu Formation (Çankırı Basin, Central Anatolia, Turkey)

The Çankırı Basin, located in the northern part of the Central Anatolian Plateau, is a large Tertiary basin where thick Miocene to Quaternary continental sediments overlay the Cretaceous-Tertiary units. This investigation focuses on the Tuğlu Formation, an Upper Miocene succession mainly composed of dark grey silty and organic rich clays. The type section of Tuğlu has been sampled for an array of multidisciplinary analyses. The palaeontological proxies included ostracod, foraminifer, nannoplankton, pollen, molluscs, charophytes, small mammal assemblages, fish, and crab remains. The abiotic parameters studied were: palaeomagnetism and environmental magnetism, stable carbon and oxygen isotope ratios (on ostracods and bulk sediment samples), strontium isotope ratios (on ostracods and foraminifera), and major elemental composition of the sediments. All analysed proxies point to a continental setting characterised by permanent water bodies affected by strong salinity oscillations. A shallow saline lake developed in a permanent freshwater lake. Barren layers, potentially linked to a short subaerial exposure, mark the end of the saline lake and the transition to a fluvial environment. Geochemical analysis confirms aridity-humidity oscillations as recorded by the micropalaeontological proxies. Analysis of small mammal assemblages refined the chronology of the Tuğlu Formation, with the onset of the deposition at the base of the mammal zone MN9 (around 11 Ma) and continuous deposition until the MN11 zone (around 8 Ma). The stable oxygen isotope records from the Tuğlu section point to Miocene delta^{18}O water values consistent with subdued topography where no prominent mountain belts were yet developed at the northern plateau margin. If correct, this suggests that at least until the end of the deposition of the Tuğlu Formation, the Çankırı Basin did not yet experience rain shadow conditions, and the regional surface uplift of the area most likely occurred after 8 Ma.

Paleosol occurrences along the Archean–Proterozoic contact in the Aravalli craton, NW India

The Archean–Proterozoic contact (APC) comprises a large scale folded surface around Udaipur in NW India. The APC is exposed on both eastern and western flanks of a synclinorium formed during thick skinned thrusting of the Archean basement and the Paleoproterozoic cover units. Paleosol occurrences on both the limbs of this structure imply an originally continuous paleoweathering horizon and not individual pockets of paleosol as seen today. Preservation of paleosol sections along the Archean–Proterozoic interface in the Aravalli craton is strongly controlled by the structural grain. Complete paleosol sections are recognized in the eastern flank of the Udaipur synclinorium in low strain regions with respect to the regional F1 and F2 folding. In this sector the Tulsi Namla paleosol section represents an ancient lateritic weathering profile with an iron depleted pallid lower zone (lithomarge) and an iron enriched upper zone (mottled zone to ferricrete). Original kaolinite in the saprolite and pallid zone has been transformed into kyanite during metamorphism and subsequently to white mica during retrograde overprint, while Fe rich clay and goethite were probably the primary minerals for the chloritoid and hematite which now constitute the upper zone. At the western flank of the synclinorium the contact is heavily sheared and Archean basement and Proterozoic units show interfingering on a small scale. Here, the paleosol sections are incomplete.The weathering interval can be inferred by the stabilization of the craton at ∼2.5Ga and deposition of rift related sequences of the Aravalli basin (Delwara formation) at ∼2.15Ga. The Udaipur paleosols, especially in the eastern flank, represent the most complete Archean–Paleoproterozoic paleosol sections in India.

Surface modification of Cameroonian magnetite rich clay with Eriochrome Black T. Application for adsorption of nickel in aqueous solution

In this study, the surface of Cameroonian magnetite rich clay was modified using Eriochrome Black T, EBT by the batch adsorption method. The EBT-modified magnetite rich clays were used for nickel ions adsorption from aqueous solution. The effect of various experimental factors; the pH of solution, the influence of concentration, the temperature, the contact time and the particle size of the sample were studied by using the batch technique. Adsorption process was better described by the pseudo-second-order kinetic and Tempkin isotherm model. The results showed that the EBT adsorption onto samples is affected by the pH of solution and the maximum EBT ion adsorption takes place between pH 2 and pH 3. The characterization of the surface modification was performed with FTIR and ZPC measurements. The FTIR shows that chemisorption took place at the surface of the bulk samples. The EBT-modified magnetite rich clay presented a binding capacity of nickel ions about 30% higher compared to the unmodified samples from an initial nickel ions concentration of 5.26mmol using 0.5g of sample.

A hybrid waveguide cell for the dielectric properties of reservoir rocks

A hybrid waveguide cell is described for broad-band measurements of the dielectric properties of hydrocarbon reservoir rocks. The cell is designed to operate in the radio frequency range of 1 MHz to 1 GHz. The waveguide consists of 50 Ω coaxial lines feeding into a central cylindrical section which contains the sample under test. The central portion of the waveguide acts as a circular waveguide and can accept solid core plugs of 38 mm diameter and lengths from 2 to 150 mm. The central section can also be used as a conventional coaxial waveguide when a central electrode with spring-loaded end collets is installed. In the latter mode the test samples are required to be in the form of hollow cylinders. An additional feature of the cell is that the central section is designed to telescope over a limited range of 1–2 mm with the application of an axial load. Effective pressures up to 35 MPa can be applied to the sample under the condition of uniaxial strain. The theoretical basis of the hybrid waveguide cell is discussed together with calibration results. Two reservoir rocks, a Donnybrook sandstone and a kaolin rich clay, are then tested in the cell, both as hollow cylinders in coaxial mode and in the form of solid core plugs. The complex dielectric properties of the two materials over the bandwidth of 1 MHz to 1 GHz are compared with the results of the two testing methods.

Iron-rich Oklahoma clays as a natural source of chromium in monitoring wells

Water samples, drawn from groundwater monitoring wells located southeast of Oklahoma City, OK, were found to contain elevated concentrations of total chromium with an apparent source localized to the area surrounding each well. Since these monitoring wells are located in areas with no historic chromium usage, industrial sources of chromium were ruled out. Water testing was performed on twelve monitoring wells in the area that historically had elevated total chromium concentrations ranging from 10-4900 micrograms per litre. Filtered water samples were found to be free of chromium contamination, indicating that the source of the chromium is the suspended solids. Analysis of these solids by acid digestion and a sequential extraction technique revealed that the chromium was primarily associated with iron-containing solids. X-ray diffraction identified goethite, an iron oxide hydroxide, as the dominant iron-containing phase in the suspended solids. The mineralogy in this region is dominated by interbedded red-bed sandstone and mudstone whose mineral content includes mixed-layer illite-smectite, hematite, goethite, gypsum and dolomite. Elemental analysis of soil samples collected as a function of depth in the locale of the monitoring wells indicated that the iron rich clays contain a natural source of chromium. The elevated levels of total chromium are most likely due to the dissolution of silica and alumina from the chromium containing iron clays in the basic well water, resulting in the release of fine suspended solids that naturally have high chromium concentrations. These results should be applicable to other areas containing iron-rich clays.

Correlations between Combustion Type Additives and Expansion after Extrusion of Clay Bricks

Experimental work was conducted on illite-chlorite and kaolinite-carbonate rich clays to investigate effects of pore forming additive materials. Three types of additives were applied: vegetal materials like sawdust, sunflower seeds hull and rice husks; lignite, as high organic content mineral material; fuel-grade coke, as synthetic additive. Raw materials were characterized regarding their composition, thermal behavior, microstructure and chemical composition. Expansion of extruded samples was detected after pressing release. Correlations were determined between the type and cellulose content of vegetal materials and expansion caused. The mineral and synthetic additive does not produce expansion, but lowers the working moisture needed.

A Comparative Evaluation of Various Additives Used in the Stabilization of Sulfate Bearing Lean Clay

Abstract A laboratory study was conducted on both raw and stabilized clay specimens to evaluate short- and long-term performance of three different additives, namely, hydrated lime, class C fly ash (CFA), and cement kiln dust (CKD), for providing better treatment of sulfate rich lean clay. Short-term performance evaluation experiments included Atterberg limits, resilient modulus (Mr), modulus of elasticity (ME), and unconfined compressive strength (UCS), after 28 days of curing. Long-term performance was evaluated in terms of moisture susceptibility (tube suction test) and three-dimensional swell during 120 days of capillary soaking. At the end of 120 days, specimens were also tested for Mr, ME, and UCS, as additional indicators to long-term pavement performance. Short-term performance evaluation projected 15 % CKD with highest improvement, while long-term performance evaluation showed 15 % CFA providing maximum enhancements after 120 days of capillary soaking. The study further indicated swelling of specimens stabilized with lime and CKD; however, CFA helped in reducing the swelling. All the percentages of additives used in the study helped in reducing the moisture susceptibility of clay. Mineralogical studies such as scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction were also used to verify research findings observed from the macro test results.

Palaeolimnology of Lake Hess (Patagonia, Argentina): multi-proxy analyses of short sediment cores

In contrast with the extensive palaeolimnological studies carried out in North America and Europe, relatively few studies have described the anthropogenic and/or climate impacts in Patagonian lakes. We addressed these issues by analysing geochemistry, lithology, pigments and chironomid remains from sediment cores collected from Lake Hess (41°22′20″S, 71°44′0″W) located in the Nahuel Huapi National Park in northern Patagonia. The aim of this study is to provide a palaeoenvironmental and climate reconstruction of the past ca. three centuries for this cold oligotrophic, quasi-pristine lake which receives meltwaters from the Tronador ice cap. Chronology was based on 137Cs and 210Pb measurements of the upper sediments, and the inferred sedimentation rate of 23.2 mg cm−2 y−1 (0.15 cm y−1) was consistent with both sets of measurements. The sediment from Lake Hess was rich in tephra deposits particularly evident in the lower part of the cores. Tephras are valuable to use for core correlation and can be traced through peaks in the magnetic susceptibility (MS) profiles. Results from the multiproxy analyses in the longest core (83 cm) identify three main phases of change. From the bottom up to 42 cm (ca. ad 1800), the sediment is composed of light-grey organically rich clays. Both pigments and chironomids suggest variable trends in productivity and precipitation regime. At the end of the Little Ice Age chronozone (ad 1770–1850), pigment concentrations were very low. From 42 cm to ca. 25 cm (ad 1800–1940), the sedimentary record is composed of alternating black and dark organic-matter rich mud with variable amounts of macrophyte remains. Pigment concentrations and chironomid head capsule counts were also very low. These facies are composed of very fine plastic sediments with some faintly laminated intervals and an organic matter composition gradually decreasing towards the top of the zone. A sharp change occurs at 25 cm (ca. ad 1940) showing a strong increase in organic matter content, algal nutrients and plant pigments together with a change in the chironomid assemblages. This might document a change in the trophic condition of the lake associated with changes in erosion/deposition rates. Although there are records of human impact in the area studied, involving the use of fires, most of the observed chemical and biological changes in Lake Hess sediment sequence were interpreted in terms of climate changes, especially to changes in moisture balance brought about by variations in the strength of the westerlies.

Accumulation of As, Pb, and Cu Associated with the Recent Sedimentary Processes in the Colorado Delta, South of the United States-Mexico Boundary

Sediment cores from the Colorado River (CR) remnant delta were used to assess the changing sedimentation and pollutant deposition processes in response to extensive human manipulation of the river. The cores are formed of alternating layers of clays and silts, with isolated sandy horizons. The clayey units are interpreted as periods of flood flows into this low gradient and meandering estuary after dam construction in the United States. The geochemistry of these sediments is particular because of the association of MnO with CaO rather than with the Fe(2)O(3)-rich clays. Past pollution of the CR delta by As, and probably also Pb and Cu, is recorded in some cores. Enrichment factors (EFs) >1 for these elements and their statistical association suggest anthropogenic inputs. The most likely sources for these element enrichments (especially As) are the arsenate-based pesticides used intensively in the area during the first half of the 20th century. The transport of these elements from the nearby agricultural lands into the present river reaches appears to have been driven in part by flooding events of the CR. Flushing by river and tide flows appear to be responsible of a lower pollutant deposition in the CR compared to the adjacent Hardy River (HR). Arsenic in the buried clay units of the HR has concentrations above the probable toxic effect level (PEL) for dwelling organisms, with maximum concentrations of 30 microg g(-1). Excess (210)Pb activities ((210)Pb(xs)) indicate that fluxes of this unsupported atmospheric isotope were not constant in this estuarine environment. However, the presence of (210)Pb(xs) does indicate that these sediments accumulated during the last ~100 years. Aproximate sediment ages were estimated from the correlation of historic flooding events with the interpretation of the stratigraphic record. They are in fair agreement with the reported onset of DDT metabolites at the bottom of one core.

Isozyme polymorphism and genetic differentiation in natural populations of an endemic tetraploid species Avena maroccana in Morocco

A wild tetraploid oat Avena maroccana Gdgr. was collected from the 11 populations in the periphery of Rommani and Casablanca geographic groups of Morocco. Genetic diversity of the species was investigated using six allozyme systems. Allelic frequencies were scored representing eight polymorphic and five monomorphic loci. Coefficient of gene differentiation (Gst) was 0.3019, which indicated great genetic differentiation. The number of alleles per locus was 2.6154, the percentage of polymorphic loci was 61.54, and the expected heterozygosity was 0.2462 in all populations. Genetic diversity in A. maroccana was high in comparison to self-pollinated species. In total, nine heterozygotes resulting from outcrossing were found in the progeny from M1, M3, M4, M22 and M26. The population of M7 had peculiar alleles Pgd-2SS and Pgd-1SS in high frequency. M9 had the lowest level of diversity out of the 11 populations. Geographic and genetic distances between all the populations were not significantly correlated with each other (r = 0.0996). Cluster analysis showed that two groups, (M1, M22, M2 and M4) and (M3, M23, M8, M5 and M26) were apparently differentiated. Two populations of the Casablanca group, M7 and M9 were independent from each other, and were separated distinctly from the other populations. Genetic diversity of the Rommani and Casablanca groups was almost the same in all the parameters. This was due to the similar man-made habitat such as roadside or rich fertile soil and brown clay soils. The population size of A. maroccana was small and restricted to the narrow central Morocco with great genetic differentiation so that genetic diversity may be reflected from the results of genetic drift and outcrossing heterozygote segregation.

Mineralogical transformations of calcareous rich clays with firing: A comparative study between calcite and dolomite rich clays from Algarve, Portugal

Mineralogical transformations during firing of two extremely calcareous clays, one calcite and other dolomite rich, and relatively poor in silica were studied. Original clays were mineralogical and chemically characterized with X-ray diffraction (XRD) and X-ray fluorescence (XRF). Firing of both clays was carried out in the temperature range 300–1100 °C under oxidizing conditions and the mineralogical transformations were investigated with XRD, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy associated with energy dispersive X-ray spectroscopy (SEM-EDS). Important compositional differences in the neoformed phases were observed between calcite and dolomite rich clays. In the Ca-rich clay the assemblage gehlenite + wollastonite + larnite was observed. In the Mg(Ca)-rich clay the reaction products included akermanite, diopside, monticellite, forsterite, periclase and spinel. XRD and SEM-EDS showed the presence, in both clays, of a potassium–calcium sulfate in samples fired between 900 and 1100 °C.

Imagining the flowers, but working the rich and heavy clay: participation and empowerment in action research for health

Participation of the ‘target group’ is a key concept in working on empowerment in health education. However, it raises many questions and is not without struggle. I will discuss the findings from a study into the state of the art of empowerment in health education, which includes a literature review and the analysis of eight Dutch health‐promotion projects. An important finding is that participation is not an unequivocal concept. Professionals working in health education strongly disagree on the value, goals and meaning of participation. Moreover, in working on empowerment, a tension exists—between the ideal of participatory, ‘bottom‐up’ approaches on the one hand; and the ‘top‐down’ structure of health education programmes, on the other. I will argue for a ‘realistic approach’ in which the practice of health promotion is taken as the starting point to work on empowerment. After all, imagining the flowers is easy, but working the rich and heavy clay is the challenge.

Evaluation of the transient electromagnetic geophysical method for stratigraphic mapping and hydrogeological delineation in Campos Basin,Brazil

The applicability of the Transient Electromagnetic (TEM) geophysical method for stratigraphic mapping and hydrogeological delineation has been tested in terrestrial part of the Campos Basin in Brazil. The study area is located within the fluvial plain of Paraiba do Sul River, at the W edge of the continental portion of the Basin, geologically consisting of Tertiary and Quaternary sediments and a gneissic basement. Around 32 central loop TEM soundings were made with 10 or20 m-sided transmitter loops, to map the conductive and/or resistive zones in the subsurface, which were correlated with lithology from a drilled borehole in the test area, whose location was indicated by the present study. In general, the one-dimensional (1D) models constructed for the TEM field data suggest a 3-layer resistivity structure characterized by a resistor-conductor-resistor pattern. The shallow section of 100-500 ohm.m and 50 m average thickness is interpreted as correlating with clay and shaly sand formations. The intermediate layer, with thickness around 20 m and resistivity less than 10 ohm.m, corresponds to clay. The basal resistor of 10-100 ohm.m at depths of more than 60 m at most sites is interpreted as the combined signature of the basal conglomerates, shaly sands and crystalline basement. Comparison with borehole data shows that the zone corresponding to the conductive geoelectrical units contains many thin layers of clay and sand that cannot be individually resolved by the TEM data and that there are no thick aquifers in the investigated area. In addition to that the shaly sand sediments have iron rich clays, which pollute groundwater, deeper resistive layers formed by conglomerates are considered the main aquifers of this area.

Low-temperature alteration and magnetic changes of variably altered pillow basalts

SUMMARY Pillow basalt fragments from the East Pacific Rise, dredged during the Phoenix expedition, often show discoloured rims due to alteration. A suite of nine pillow basalts with such discoloured rims and ranging in age between 200 and 820 ka has been characterized in terms of their Fe‐Ti-oxide mineralogy and rock magnetic properties. These large pillow fragments show relatively unaltered grey interiors, surrounded by darker, concentric halos, which vary in thickness as measured from glassy pillow rims and surfaces caused by large cracks penetrating into the original pillow interior. The discoloured zones are characterized by precipitation of abundant secondary minerals, such as Fe 3+ -rich clays that filled vesicle spaces. Fe‐Ti oxides in subsamples from discoloured rims and grey interiors have been investigated with electron microscopy and rock magnetic techniques. The subsamples come from traverses that are parallel to the outer glassy pillow rims, allowing us to study the low-temperature alteration effects and rock magnetic properties without having to take variable grain size into account. Not surprisingly, titanomaghemites in discoloured rims are, in a general sense, oxidized to a higher degree (z typically >0.55) than those in the relatively unaltered grey interior (z typically 0.6 within 200 000 yr. The difference between the oxidation states of titanomaghemite within the grey pillow interior and the discoloured rims gradually diminishes with increasing age, so that for samples with ages of 800 ka the oxidation state of titanomaghemites in the grey interior approaches that of the discoloured rim. Our study demonstrates that visible discolouration of pillow basalts is not a suitable proxy for z. Because average Ti content can vary from sample to sample, Curie temperatures are also inaccurate proxies for z .I fone wants to study possible correlations between z and rock magnetic parameters, the best technique is to determine z for each subsample by using trans° )

Errata for “Dynamic Properties of Chemically Stabilized Sulfate Rich Clay”

Errata for “Dynamic Properties of Chemically Stabilized Sulfate Rich Clay”