The role of structural iron oxidation in the weathering of trioctahedral micas by aqueous solutions

An integrated approach involving several experimental and analytical techniques was used to study the role of structural iron oxidation in the weathering of trioctahedral micas by aqueous solutions. Analytical techniques for the assay of Fe(II) by oxidimetry and for the estimation of octahedral sheet cation occupancies by x-ray diffraction were developed. A weathering apparatus to allow the continuous treatment of micas by fresh aqueous solutions was also developed. This apparatus was used to treat the 10- to 20-[mu]m size-fractions of three trioctahedral micas (a phlogopite, biotite, and siderophyllite) by aqueous solutions that varied in their tendency to promote oxidation, dissolution, and interlayer expansion reactions in the micas. The treatments generally involved 1 M KOAc(pH 4.7)-0.1 M K[subscript]2 EDTA solutions with or without 25% H[subscript]2O[subscript]2 as an oxidant, and were applied at 80°C for periods as long as 36 days. Experiments with deuterated mica samples and with K-depleted samples in 1 M Na solutions were also conducted. The time-dependence of the dissolution of the micas was determined by measuring the amounts of Al, Mg, and Fe in the effluent solutions after different periods and calculating apparent rate constants (ca. 10[superscript]-4 s[superscript]-1) using a heterogeneous kinetic model. Ratios of the rate constants obtained in different solutions were used to estimate the extent of exfoliation of the micas by the weathering treatments. Structural and chemical analyses of the micas before and after treatment were performed by conventional techniques (x-ray diffraction, infrared spectroscopy, Mossbauer spectroscopy) in addition to the two techniques that were developed. These analyses provided strong evidence for the deprotonation of structural hydroxyls and ejection of octahedral cations during the oxidation treatments and for the existence of vacant tetrahedral sites in micas. The main conclusions reached were (1) oxidation of structural Fe(II) in trioctahedral micas does not occur in aqueous solutions without an associated expansion or exfoliation of the interlayer region; (2) the charge created by oxidation is balanced by a combination of the deprotonation of structural hydroxyls, the ejection of octahedral cations (trivalent preferentially to divalent), and the loss of interlayer cations, and (3) the K-selectivity of the mica plays a key role in determining whether oxidation will occur in high-K solutions

Letter Report for Characterization of Biochar

On 27 November 2012, a bulk biochar sample was received for characterization of selected physical and chemical properties. The main purpose of the characterization was to help determine the degree to which biochar would be suitable as a soil amendment to aid in growth of plants. Towards this end, analyses to determine specific surface, pH, cation-exchange capacity, water retention, and wettability (i.e. surface tension) were conducted. A second objective was to determine how uniform these properties were in the sample. Towards this end, the sample was separated into fractions based on initial particle size and on whether the material was from the external surface or the internal portion of the particle. Based on the results, the biochar has significant liming potentials, significant cation-retention capacities, and highly variable plant-available moisture retention properties that, under the most favorable circumstances, could be helpful to plants. As a consequence, it would be quite suitable for addition to acidic soils and should enhance the fertility of those soils

Mechanisms of CCl4 Retention and Slow Release in Model Porous Solids and Sediments

Provide a better description of the processes by which non-polar compounds are retained by sediments and subsequently released. The objective will be reached through a combination of theory and experimentation with model porous materials and natural sediments. Focus is on the behavior of carbon tetrachloride in aquifer sediments

Synthesis of Colloidal Mn2+:ZnO Quantum Dots and High-TC Ferromagnetic Nanocrystalline Thin Films

We report the synthesis of colloidal Mn2+-doped ZnO (Mn2+:ZnO) quantum dots and the preparation of room-temperature ferromagnetic nanocrystalline thin films. Mn2+:ZnO nanocrystals were prepared by a hydrolysis and condensation reaction in DMSO under atmospheric conditions. Synthesis was monitored by electronic absorption and electron paramagnetic resonance (EPR) spectroscopies. Zn(OAc)2 was found to strongly inhibit oxidation of Mn2+ by O2, allowing the synthesis of Mn2+:ZnO to be performed aerobically. Mn2+ ions were removed from the surfaces of as-prepared nanocrystals using dodecylamine to yield high-quality internally doped Mn2+:ZnO colloids of nearly spherical shape and uniform diameter (6.1 +/- 0.7 nm). Simulations of the highly resolved X- and Q-band nanocrystal EPR spectra, combined with quantitative analysis of magnetic susceptibilities, confirmed that the manganese is substitutionally incorporated into the ZnO nanocrystals as Mn2+ with very homogeneous speciation, differing from bulk Mn2+:ZnO only in the magnitude of D-strain. Robust ferromagnetism was observed in spin-coated thin films of the nanocrystals, with 300 K saturation moments as large as 1.35 Bohr magneton/Mn2+ and TC > 350 K. A distinct ferromagnetic resonance signal was observed in the EPR spectra of the ferromagnetic films. The occurrence of ferromagnetism in Mn2+:ZnO and its dependence on synthetic variables are discussed in the context of these and previous theoretical and experimental results.Comment: To be published in the Journal of the American Chemical Society Web on July 14, 2004 (http://dx.doi.org/10.1021/ja048427j

Multi-Channel Auto-Dilution System for Remote Continuous Monitoring of High Soil-CO2 Fluxes

Geological sequestration has the potential capacity and longevity to significantly decrease the amount of anthropogenic CO2 introduced into the atmosphere by combustion of fossil fuels such as coal. Effective sequestration, however, requires the ability to verify the integrity of the reservoir and ensure that potential leakage rates are kept to a minimum. Moreover, understanding the pathways by which CO2 migrates to the surface is critical to assessing the risks and developing remediation approaches. Field experiments, such as those conducted at the Zero Emissions Research and Technology (ZERT) project test site in Bozeman, Montana, require a flexible CO2 monitoring system that can accurately and continuously measure soil-surface CO2 fluxes for multiple sampling points at concentrations ranging from background levels to several tens of percent. To meet this need, PNNL is developing a multi-port battery-operated system capable of both spatial and temporal monitoring of CO2 at concentrations from ambient to at least 150,000 ppmv. This report describes the system components (sampling chambers, measurement and control system, and power supply) and the results of a field test at the ZERT site during the late summer and fall of 2008. While the system performed well overall during the field test, several improvements to the system are suggested for implementation in FY2009

Speed and Agility Prediction Models in High School Football Players

Background: Optimal relationships between speed, agility, power and body mass are essential in American football. An increase in body mass, theoretically, reduces acceleration (Newton’s 2nd Law). However, an increase in lean body mass may enhance overall force or power generating potential and momentum of an athlete. Body mass, height, and vertical jump height are routinely measured, easily obtainable, and may be used as predictors of speed and agility. Purpose: To determine associations between height, vertical jump height, and body mass to speed and agility in high school football players. Methods: Data were collected on 1261 male football players (16.4±0.9yrs, 179.7±6.9cm, 87.5±18.4kg) at a regional football combine. In successive order, each athlete completed the following tests: height (HT; cm), body mass (BM; kg), 40-yard sprint (SP; s), pro-agility (AG; s), and vertical jump (VJ; cm). The data were collected after a self selected warm-up and athletes were provided three trials on performance drills. HT was measured using a standard stadiometer and BM using a calibrated scale. SP and AG times were measured with hand held stop watches. Finally, a contact mat was used to measure flight time during a countermovement VJ; subsequently VJ height was calculated from flight time using freely falling body equations. Model prediction equations for SP and AG were generated using SigmaStat statistical software package. For each equation, HT, BM, and VJ were set as predictor variables. Non-significant variables were eliminated from the model with an alpha level of p \u3c 0.05. Results: VJ (R=-0.73), BM (R= 0.67), and HT (R = 0.17), were all significant predictors of SP. The combined regression model SP(s) = 6.60561–0.0217VJ+0.00753BM– 0.00438HT explains 73% of the variance in forty yard sprint time (R=0.086; SEE =0.20). HT (R=0.08), BM (R=0.44), and VJ (-0.62) were significantly correlated with AG and were included in the combined regression model: AG(s) = 6.479-0.00437HT+0.00394BM-0.0180VJ (R=0.40; SEE=0.304). Conclusions: HT, VJ, and BM are strong predictors of linear speed. American football players may be able to increase speed by engaging in exercise programs that reduce body mass and improve vertical ground reaction force production. However, these data suggest that HT, BM, and VJ are not as strong of predictors of agility. Future research should address associations between other potential testing constructs and agility in American football players

Project Work Plan Carbon Tetrachloride and Chloroform Attenuation Parameter Studies: Heterogeneous Hydrolytic Reactions

Between 1955 and 1973, an estimated 750,000 kg of carbon tetrachloride were discharged to the soil in the 200 West Area of the Hanford Site as part of the plutonium production process. Of this amount, some carbon tetrachloride reached the groundwater more than 70 m below the ground surface and formed a plume of 10 km2. Recent information has shown that the carbon tetrachloride plume extends to a depth of at least 60 m below the water table. Some carbon tetrachloride has been degraded either by the original process or subsequent transformations in the subsurface to form a co-existing chloroform plume. Although current characterization efforts are improving the conceptual model of the source area, more information is needed to effectively assess the fate and transport of carbon tetrachloride and chloroform to support upcoming remediation decisions for the plume. As noted in a simulation study by Truex et al. (2001), parameters describing porosity, sorption, and abiotic degradation have the largest influence on predicted plume behavior. The work proposed herein will improve the ability to predict future plume movement by better quantifying abiotic degradation mechanisms and rates. This effort will help define how much active remediation may be needed and estimate where the plume will eventually stabilize – key factors in determining the most appropriate remedy for the plume

Reliability of Unilateral Isometric and Dynamic Leg Press Force and Power

Strength and power are critical components of athletic performance. Athletes commonly perform sport-specific movements off a single leg, but there are few reliable, easily administered unilateral leg force and power assessments. PURPOSE: To determine 1) the reliability of unilateral leg press maximal isometric force (MIF) and peak power tests and 2) the percentage of MIF that elicits unilateral peak power during a dynamic throw. We hypothesized that the tests would be reliable for the assessment of unilateral MIF and peak power and that unilateral peak power would be achieved at 50% of MIF. METHODS: Eighteen apparently healthy, recreationally active adults (17M: 1F; 27.4 ± 5.0 years; 1.78 ± 0.01 m; 93.5 ± 22.5 kg; 3159 ± 807 N bilateral MIF) completed three testing sessions. After a brief standardized warm-up, each subject performed three maximal unilateral isometric leg presses (MIF) with each leg at 90° of knee flexion on a modified leg press sled equipped with a force plate, linear encoder, and magnetic brake. Subsequently, the sled was unlocked and loaded in ascending fashion with 30%, 40%, 50%, 60%, and 70% of MIF; with an initial knee angle of 90°, subjects used maximal effort to throw each load twice, unilaterally, with each leg. Subjects rested and reset for 10-30 s between efforts. Data were sampled at 300 Hz, low pass filtered at 4 Hz, and peak instantaneous power (W) was calculated for each throw using the measured sled force and velocity. Intraclass correlation coefficients (ICC) were computed for the highest force and power repetition at each load across the three sessions. The ICC (95% CI) and peak power output were determined for both right and left legs. ICCs were considered excellent if ≥ 0.95, high if ≥ 0.90, good if ≥ 0.80, fair if ≥ 0.70, poor if ≤ 0.70, and very poor if ≤ 0.40. RESULTS: MIF showed good reliability between sessions [ICC: 0.85 (0.62, 0.94; left leg); 0.86 (0.58, 0.95; right leg)]. Unilateral peak power also showed good to high reliability between sessions across all loads: ICC (left leg) 30%: 0.91 (0.81, 0.96); 40%: 0.91 (0.81, 0.96); 50%: 0.95 (0.88, 0.98); 60%: 0.93 (0.86, 0.97); 70%: 0.81 (0.64, 0.92); (right leg) 30%: 0.95 (0.89, 0.98); 40%: 0.94 (0.87, 0.97); 50%: 0.92 (0.84, 0.97); 60%: 0.92 (0.84, 0.97); 70%: 0.90 (0.80, 0.96). Across all three sessions, peak power by the left leg was achieved at: 30% (11 of 18 participants); 40% (6 of 18); 50% (1 of 18). Peak power by the right leg was achieved at: 30% (13 of 18 participants); 40% (4 of 18); 50% (1 of 18). CONCLUSION: Unilateral leg press MIF and peak power can be reliably assessed with a modified leg press equipped with a force plate, linear encoder, and magnetic brake in a recreationally active population. Sport teams and coaches can use single leg isometric presses and throws as reliable methods to test their athletes’ unilateral force and peak power, respectively, with loads of 30-50% MIF appropriate for peak power measurement

Influence of soil minerals on chromium(VI) reduction by sulfide under anoxic conditions

The effects of soil minerals on chromate (Cr(VI)O(4)(2-), noted as Cr(VI)) reduction by sulfide were investigated in the pH range of 7.67 to 9.07 under the anoxic condition. The examined minerals included montmorillonite (Swy-2), illite (IMt-2), kaolinite (KGa-2), aluminum oxide (γ-Al(2)O(3)), titanium oxide (TiO(2), P-25, primarily anatase), and silica (SiO(2)). Based on their effects on Cr(VI) reduction, these minerals were categorized into three groups: (i) minerals catalyzing Cr(VI) reduction – illite; (ii) minerals with no effect – Al(2)O(3); and (iii) minerals inhibiting Cr(VI) reduction- kaolinite, montmorillonite, SiO(2 )and TiO(2 ). The catalysis of illite was attributed primarily to the low concentration of iron solubilized from the mineral, which could accelerate Cr(VI) reduction by shuttling electrons from sulfide to Cr(VI). Additionally, elemental sulfur produced as the primary product of sulfide oxidation could further catalyze Cr(VI) reduction in the heterogeneous system. Previous studies have shown that adsorption of sulfide onto elemental sulfur nanoparticles could greatly increase sulfide reactivity towards Cr(VI) reduction. Consequently, the observed rate constant, k(obs), increased with increasing amounts of both iron solubilized from illite and elemental sulfur produced during the reaction. The catalysis of iron, however, was found to be blocked by phenanthroline, a strong complexing agent for ferrous iron. In this case, the overall reaction rate at the initial stage of reaction was pseudo first order with respect to Cr(VI), i.e., the reaction kinetics was similar to that in the homogeneous system, because elemental sulfur exerted no effect at the initial stage prior to accumulation of elemental sulfur nanoparticles. In the suspension of kaolinite, which belonged to group (iii), an inhibitive effect to Cr(VI) reduction was observed and subsequently examined in more details. The inhibition was due to the sorption of elemental sulfur onto kaolinite, which reduced or completely eliminated the catalytic effect of elemental sulfur, depending on kaolinite concentration. This was consistent with the observation that the catalysis of externally added elemental sulfur (50 μM) on Cr(VI) reduction would disappear with a kaolinite concentration of more than 5.0 g/L. In kaolinite suspension, the overall reaction rate law was: -d[Cr(VI)]/dt = k(obs)[H(+)](2)[Cr(VI)][HS(-)](0.70