Escherichia coli O157 survival in liquid culture and artificial soil microcosms with variable pH, humic acid and clay content.

AIMS: This research was performed to investigate the influence of clay and humic acid on Escherichia coli O157 survival in model soils. Additionally, the influence of pH and humic acid on E. coli O157 in liquid culture was investigated. METHODS AND RESULTS: Artificial soil microcosms were prepared with sand, kaolinite, bentonite and humic acid. Artificial soil microcosms pH was adjusted (6·0-7·0) with aluminium sulphate before E. coli O157 inoculation. After 56 days of incubation at 30°C, significant differences in E. coli O157 log CFU per gram were observed between 0 and 1000 ppm (P < 0·0001) and 0 and 5000 ppm (P < 0·0001) humic acid in 1·5% clay soils, but not in 7·5 or 15% clay soils. Significant differences (P < 0·05) in E. coli O157 log CFU per ml were observed in liquid culture influenced by humic acid concentrations after 8 h at 37°C. CONCLUSIONS: The developed model soils support E. coli O157 populations over 28 days, and higher clay soils may aid in E. coli O157 survival. SIGNIFICANCE AND IMPACT OF THE STUDY: These results provide insights into physicochemical properties of soil that may influence E. coli O157 in the environment and help explain E. coli O157 survival in various soils and geographical regions.

Forsythiae Fructus aqueous extract attenuates cisplatin-induced kaolin consumption (pica) by inhibiting NLRP3 inflammasome activation in rats.

The present study was conducted to evaluate the effect of Forsythiae Fructus aqueous extract (FAE) against cisplatin-induced emesis and to explore the antiemetic mechanism of FAE by focusing on NLRP3 inflammasome activation in a rat pica model. Our results showed that FAE significantly ameliorated cisplatin-induced acute and delayed pica in rats. Moreover, FAE improved the gastrointestinal histopathological injury and reduced the levels of serum ROS, IL-1ß, and IL-18 in cisplatin-treated rats. In addition, the expressions of NLRP3, ASC, caspase-1, and IL-1ß and the colocalization of the NLRP3 with ASC or caspase-1 in rat gastric antrum and ileum were also suppressed by FAE. Taken together, our findings indicate that FAE has a therapeutic effect against CINV, which may be related to its inhibition of the activation of NLRP3 inflammasome.

Gliding arc plasma pre-treatment of kaolin in spatial post-discharge mode for removal of Reactive Red 2 dye from aqueous solution.

This study investigates the ability of spatial post-discharge mode functionalized kaolin to remove textile dye Reactive Red 2 from aqueous solution compared to that of the raw kaolinite. To fulfill the aim, the removal conditions, including plasma exposure time, processed mode (direct and post-discharge), pH of the aqueous dye solution, initial dye concentration and adsorbent dosage, were investigated. The changes that occur on clay surfaces before and after gliding arc plasma treatment were followed by Fourier transform infrared spectroscopy, scanning electron microscopy and nitrogen physisorption. The point of zero charge and the changes of the textural properties after gliding arc plasma treatment were also examined. The experimental data were analyzed using pseudo-first-order, pseudo-second-order and empirical Elovich models. The diffusion phenomenon was also studied. The results obtained indicate that spatial post-discharge pre-treatment of kaolin deeply influences the functional groups of some of its minerals as well as the morphology and texture of its particles. Consequently, at room temperature (∼30 °C), the maximum adsorption capacities of natural raw kaolin clay were tripled after treatment with gliding arc plasma in spatial post-discharge mode and were almost doubled after the direct treatment mode.

Synthesis of a novel magnetic polyacrylamide coagulant and its application in wastewater purification.

In this study, a novel magnetic polyacrylamide (PAM) coagulant based on the core of magnetite (Fe3O4), with oleic acid serving as modifier and acrylamide as monomer, was synthesized to remove suspended solids in kaolin-suspended water. The composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermo gravimetric analysis and scanning electron microscopy. The results demonstrated that 82.8% of turbidity removal rate was obtained in 5 min of static settling in simulated kaolin-suspended water. This proved to be superior to that of PAM and poly aluminum chloride. Also confirmed in this study was the fact that zeta potential was significantly correlated with turbidity removal.

Cationic polyelectrolyte induced separation of some inorganic contaminants and their mixture (zirconium silicate, kaolin, K-feldspar, zinc oxide) as well as of the paraffin oil from water.

The flocculation efficiency of a cationic polyelectrolyte with quaternary ammonium salt groups in the backbone, namely PCA5 was evaluated on zirconium silicate (kreutzonit), kaolin, K- feldspar and zinc oxide (ZnO) suspensions prepared either with each pollutant or with their mixture. The effect of several parameters such as settling time, polymer dose and the pollutant type on the separation efficacy was evaluated and followed by optical density and zeta potential measurements. Except for ZnO, the interactions between PCA5 and suspended particles led to low residual turbidity values (around 4% for kreutzonit, 5% for kaolin and 8% for K-feldspar) as well as to the reduction of flocs settling time (from 1200 min to 30 min and 120 min in case of kaolinit and K-feldspar, respectively), that meant a high efficiency in their separation. The negative value of the zeta potential and flocs size measurements, at the optimum polymer dose, point to contribution from charge patch mechanism for the particles flocculation. A good efficiency of PCA5 in separation of paraffin oil (a minimum residual turbidity of 9.8%) has been also found.

Evaluation of the Dustiness of Different Kaolin Samples.

Several samples of kaolin with different mean particle size were prepared and tested using the continuous drop method, one of the reference test methods according to standard EN 15051:2006 "Workplace atmospheres - Measurement of the dustiness of bulk materials - Requirements and reference test methods." On the other hand, with a view to relating the dustiness of the materials to their properties, particle size distribution, specific surface area, and Hausner ratio of these samples were determined. This article presents a characterization of these samples and an assessment of the influence of some material parameters on dustiness. The results show that dustiness may significantly be affected by mean particle size, specific surface area, and Hausner ratio. Moreover, it is highlighted that a detailed study of the influence of fine particles content on the dustiness was carried out. This information is deemed essential for establishing the most efficient preventive and/or corrective measures to reduce the generation of fugitive emissions of particulate matter during kaolin processing, both into the outside atmosphere (air pollution) and inside the facilities (occupational health).

Noachian and more recent phyllosilicates in impact craters on Mars.

Hundreds of impact craters on Mars contain diverse phyllosilicates, interpreted as excavation products of preexisting subsurface deposits following impact and crater formation. This has been used to argue that the conditions conducive to phyllosilicate synthesis, which require the presence of abundant and long-lasting liquid water, were only met early in the history of the planet, during the Noachian period (> 3.6 Gy ago), and that aqueous environments were widespread then. Here we test this hypothesis by examining the excavation process of hydrated minerals by impact events on Mars and analyzing the stability of phyllosilicates against the impact-induced thermal shock. To do so, we first compare the infrared spectra of thermally altered phyllosilicates with those of hydrated minerals known to occur in craters on Mars and then analyze the postshock temperatures reached during impact crater excavation. Our results show that phyllosilicates can resist the postshock temperatures almost everywhere in the crater, except under particular conditions in a central area in and near the point of impact. We conclude that most phyllosilicates detected inside impact craters on Mars are consistent with excavated preexisting sediments, supporting the hypothesis of a primeval and long-lasting global aqueous environment. When our analyses are applied to specific impact craters on Mars, we are able to identify both pre- and postimpact phyllosilicates, therefore extending the time of local phyllosilicate synthesis to post-Noachian times.

Consideration of kaolinite interference correction for quartz measurements in coal mine dust.

Kaolinite interferes with the infrared analysis of quartz. Improper correction can cause over- or underestimation of silica concentration. The standard sampling method for quartz in coal mine dust is size selective, and, since infrared spectrometry is sensitive to particle size, it is intuitively better to use the same size fractions for quantification of quartz and kaolinite. Standard infrared spectrometric methods for quartz measurement in coal mine dust correct interference from the kaolinite, but they do not specify a particle size for the material used for correction. This study compares calibration curves using as-received and respirable size fractions of nine different examples of kaolinite in the different correction methods from the National Institute for Occupational Safety and Health Manual of Analytical Methods (NMAM) 7603 and the Mine Safety and Health Administration (MSHA) P-7. Four kaolinites showed significant differences between calibration curves with as-received and respirable size fractions for NMAM 7603 and seven for MSHA P-7. The quartz mass measured in 48 samples spiked with respirable fraction silica and kaolinite ranged between 0.28 and 23% (NMAM 7603) and 0.18 and 26% (MSHA P-7) of the expected applied mass when the kaolinite interference was corrected with respirable size fraction kaolinite. This is termed "deviation," not bias, because the applied mass is also subject to unknown variance. Generally, the deviations in the spiked samples are larger when corrected with the as-received size fraction of kaolinite than with the respirable size fraction. Results indicate that if a kaolinite correction with reference material of respirable size fraction is applied in current standard methods for quartz measurement in coal mine dust, the quartz result would be somewhat closer to the true exposure, although the actual mass difference would be small. Most kinds of kaolinite can be used for laboratory calibration, but preferably, the size fraction should be the same as the coal dust being collected.

Multicomponent Measurement of Respirable Quartz, Kaolinite and Coal Dust using Fourier Transform Infrared Spectroscopy (FTIR): A Comparison Between Partial Least Squares and Principal Component Regressions.

Exposure to respirable crystalline silica (RCS) is potentially hazardous to the health of thousands of workers in Great Britain. Both X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy can be used to measure RCS to assess exposures. The current method outlined in the Health and Safety Executive's (HSE) Methods for the Determination of Hazardous Substances (MDHS) guidance series is 'MDHS 101 Crystalline silica in respirable airborne dust - Direct-on-filter analyses by infrared spectroscopy or x-ray'. This describes a procedure for the determination of time-weighted average concentrations of RCS either as quartz or cristobalite in airborne dust. FTIR is more commonly employed because it is less expensive, potentially portable and relatively easy to use. However, the FTIR analysis of RCS is affected by spectral interference from silicates. Chemometric techniques, known as Partial Least Squares Regression (PLSR) and Principal Component Regression (PCR), are two computational processes that have the capability to remove spectral interference from FTIR spectra and correlate spectral features with constituent concentrations. These two common chemometric processes were tested on artificial mixtures of quartz and kaolinite in coal dust using the same commercially available software package. Calibration, validation and prediction samples were prepared by collecting aerosols of these dusts onto polyvinylchloride (PVC) filters using a Safety in Mines Personal Dust Sampler (SIMPEDS) respirable cyclone. PCR and PLSR analyses were compared when processing the same spectra. Good correlations between the target values, measured using XRD, were obtained for both the PCR and PLSR models e.g. 0.98-0.99 (quartz), 0.98-0.98 (kaolinite) and 0.96-0.97 (coal). The level of agreement between PCR and PLSR was within the 95% confidence value for each analyte. Slight differences observed between predicted PCR and PLSR values were due to the number of optimal principal components applied to each chemometric process. The presence of kaolinite in these samples caused an 18% overestimation of quartz, for the FTIR, when following MDHS 101 without a chemometric method. Chemometric methods are a useful approach to obtain interference-free results for the measurement of RCS from some workplace environments and to provide a multicomponent analysis to better characterise exposures of workers.

Application of a Fourier Transform Infrared (FTIR) Principal Component Regression (PCR) Chemometric Method for the Quantification of Respirable Crystalline Silica (Quartz), Kaolinite, and Coal in Coal Mine Dusts from Australia, UK, and South Africa.

This article describes the approach used to assess the performance of a Fourier transform infrared (FTIR) and principal component regression (PCR) chemometric method when measuring respirable quartz, kaolinite, and coal in samples from a variety of mines from different countries; relative to target assigned values determined using X-ray diffraction (XRD). For comparison, FTIR results using the partial least squares regression (PLSR) method are also available. Bulk dusts from 10 Australian mines were scanned using XRD and grouped into three sets based on the levels of quartz, kaolinite, and feldspar within their crystalline mineral composition. Prediction samples were generated from 5 of these Australian mine dusts, Durrans coal dust, 2 mine dusts from the UK, and a single South African mine dust (71 samples in total) by collecting the aerosolized respirable dust onto 25-mm diameter polyvinylchloride filters using the Safety in Mines Personal Dust Sampler (SIMPEDS) operating at 2.2 l min-1. The predicted values from the FTIR chemometric methods were compared with assigned target values determined using a direct on-aerosol filter XRD analysis method described in Method for the Determination of Hazardous Substances (MDHS) 101. Limits of detection (LOD) and uncertainty values for each analyte were calculated from a linear regression between target and predicted values. The uncertainty was determined using the calibration uncertainty equation for an unweighted regression. FTIR results from PCR and PLSR are very similar. For the PCR method, the LOD for quartz, kaolinite, and coal were 5, 25, and 71 µg, respectively. For quartz, an LOD of 5 µg corresponds to an airborne quartz concentration of 10 µg m-3, assuming a 4-h sampling time and collection flow rate of 2.2 l min-1. The FTIR measurement met the expected performance criteria outlined in ISO 20581 when sampling quartz for more than 4 h using a flow rate of 2.2 l min-1 at a concentration of 0.1 mg m-3 (100 µg m-3), the current workplace exposure limit in Great Britain. This method met the same performance criteria when measuring exposures at the Australian Workplace Exposure Standard (WES) concentration of 0.05 mg m-3, although in this case a sampling period greater than 8 h was needed.

Role of clay content in partitioning, uptake and toxicity of zinc in the earthworm Eisenia fetida.

We studied the effect of clay content on the bioavailability of zinc to pre-clitellate earthworm, Eisenia fetida in the laboratory using OECD artificial soil adjusted to 5%, 20%, and 40% clay. Batches of worms were exposed to a wide range of zinc concentrations. Mortality, growth, maturation (% clitellate), cocoon production, and body zinc concentrations were assessed over and after a period of 4 weeks. Total, DTPA, and CaCl(2) extractable zinc in the substrates were also determined. The results of the biological responses showed that interaction of clay and zinc had a significant influence on mortality but not on the other biological parameters. None of the three extraction methods showed consistent and significant effect of clay content on zinc partitioning. Although total, DTPA, and CaCl(2) extracts of zinc correlated strongly with one another and were in similar relation with the observed biological responses, only the CaCl(2) extract revealed a time dependent availability of this metal. It is concluded that clay content had no significant influence on sub-lethal toxicity of zinc to this earthworm over the range of exposure concentrations.

Abundance, chemical composition and lead adsorption properties of sedimentary colloids in a eutrophic shallow lake.

Colloidal particles are omnipresent in lake sediments and substantially influence the retention, transportation, and fate of contaminants in lake ecosystems. In this study, the abundance, chemical composition and adsorption behavior of sedimentary colloids (including total and inorganic colloids) from different ecological regions, were for the first time investigated via ultrasonic extraction, spectral analysis and batch absorption experiments. Results showed that the extraction efficiencies of sedimentary colloids showed an ultrasonic energy-dependent enhancement, and the algae-dominated area contained comparable colloidal abundance with the macrophyte-dominated area (i.e., 198.5 vs. 183.3 mg/g). Despite the different ecosystems, these sedimentary colloids usually had a wide size distribution of 30-200 nm, and were characterized with montmorillonite-, kaolin-, volkonskoite-, and quartz-rich chemical compositions. Batch experiment showed that the total pristine colloids exhibited higher adsorption capacity for Pb(II) than the inorganic colloids both for the macrophyte- and algae-dominated sediments, and the adsorption process followed pseudo-second-order kinetics and Langmuir isotherm, irrespective of different colloidal types. Thus, sedimentary colloids can immobilize the heavy metals in sediment and decrease their release into the water column, which can be considered as a sink for contaminants. This study highlighted the significance of sedimentary colloids in determining the physicochemical properties of lake sediments and in evaluating the environmental behavior and fate of contaminants in lake ecosystems.

Radiative transfer model for aerosols at infrared wavelengths for passive remote sensing applications: revisited.

We introduced a two-dimensional radiative transfer model for aerosols in the thermal infrared [Appl. Opt.45, 6860-6875 (2006)APOPAI0003-693510.1364/AO.45.006860]. In that paper we superimposed two orthogonal plane-parallel layers to compute the radiance due to a two-dimensional (2D) rectangular aerosol cloud. In this paper we revisit the model and correct an error in the interaction of the two layers. We derive new expressions relating to the signal content of the radiance from an aerosol cloud based on the concept of five directional thermal contrasts: four for the 2D diffuse radiance and one for direct radiance along the line of sight. The new expressions give additional insight on the radiative transfer processes within the cloud. Simulations for Bacillus subtilis var. niger (BG) bioaerosol and dustlike kaolin aerosol clouds are compared and contrasted for two geometries: an airborne sensor looking down and a ground-based sensor looking up. Simulation results suggest that aerosol cloud detection from an airborne platform may be more challenging than for a ground-based sensor and that the detection of an aerosol cloud in emission mode (negative direct thermal contrast) is not the same as the detection of an aerosol cloud in absorption mode (positive direct thermal contrast).

Workplace monitoring of occupational exposure to refractory ceramic fiber--a 17-year retrospective.

This article presents a 17-year (1990-2006) retrospective summary of ongoing studies of occupational exposure to refractory ceramic fiber (RCF) in the United States. Beginning in 1990, RCF producers integrated and harmonized individual workplace monitoring programs to provide data useful for various longitudinal and cross-sectional analyses, benchmarking, and various technical analyses. For 10 of these 17 years, the program has been conducted in partnership with government agencies, first a 5-year (1993-1998) program with the U.S. Environmental Protection Agency and later another 5-year (2002-2006) program with the Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health. This article updates earlier published studies and provides lessons to be learned in the design of industrial hygiene monitoring and control programs.

Preparation and sorption properties of materials from paper sludge.

Three materials were prepared from paper sludge (PS) using different treatment processes and their sorption abilities for phosphate and methylene blue (MB) were determined. The samples were a powder sample prepared by heating PS in air (sample C), a pellet prepared by grinding, forming and heating PS in air (sample G) and a powder prepared by physical activation of PS in flowing wet nitrogen (sample A). The three samples were heated at 600-900 degrees C for 6h. On heating at 700-800 degrees C, the organic fibers, limestone (CaCO3), kaolinite (Al2Si2O5(OH)4) and talc (Mg3Si4O10(OH)2) in the original PS were converted to amorphous CaO-Al2O3-SiO2 (CAS) and talc in sample C, while CAS was formed in sample G and activated carbon, CAS and talc was formed in sample A. On heating at 900 degrees C the CAS converted to gehlenite (Ca2Al2SiO7) and anorthite (CaAl2Si2O8). The specific surface areas (SBET) of the three samples achieved maximum values of 23, 37 and 70 m2/g upon heating at 700, 600 and 600 degrees C, respectively. The SBET value of the activated sample A was distinctly lower than usually reported for activated carbon. The samples C, G and A achieved maximum phosphate sorption capacities of 2.04, 1.38 and 1.70 mmol/g, calculated from the Langmuir model, upon heating at 700, 700 and 800 degrees C, respectively. The maximum sorption capacity for phosphate in sample C is attributed to the sorption by CAS, namely, adsorption on the alumina component and precipitation as Ca-phosphates. The MB multifunctional sorption capacity of sample A was 0.11 mmol/g. The phosphate and MB sorption rates show better correlation with a pseudo-second order model than with other models.

Evaluation of quicklime mixing for the remediation of petroleum contaminated soils.

Quicklime mixing is an established solidification/stabilization technique to improve mechanical properties and immobilise contaminants in soils. This study examined the effects of quicklime mixing on the concentrations and leachability of petroleum hydrocarbon compounds, in two natural soils and on a number of artificial sand/kaolinite mixtures. Several independent variables, such as clay content, moisture content and quicklime content were considered in the study. After mixing the soils with the quicklime, pH, temperature, moisture content, Atterberg limits and concentrations of petroleum hydrocarbon compounds were determined on soil and leachate samples extracted from the treated soils. Significant decreases in concentrations of petroleum hydrocarbon compounds were measured in soils and leachates upon quicklime mixing, which may be explained by a number of mechanisms such as volatilization, degradation and encapsulation of the hydrocarbon compounds promoted by the quicklime mixing. The increase in temperature due to the exothermic hydration reaction of quicklime when in contact with porewater helps to volatilize the light compounds but may not be entirely responsible for their concentration decreases and for the decrease of heavy aliphatics and aromatics concentrations.

Concentration of copper and a copper-EDTA complex at the pH junction formed in soil by an electrokinetic remediation process.

The formation and stability of a pH junction was investigated, and the precipitation and accumulation of a metal hydroxide at the pH junction was confirmed. Moreover, the possibility that metal ions could be accumulated as a Me-EDTA complex at the pH junction was demonstrated. As a result, the pH junction where the acidic and alkali fronts of soil meet and the pH of soil changes rapidly, appeared at the 0.6 position in the EK process for 6-12 h. Copper ions accumulated in the form of copper hydroxide. EDTA was also concentrated in the position, in general agreement with the position of the pH junction. In addition to copper hydroxide, a copper-EDTA complex was concentrated at the 0.6 position from the anode after EK treatment for 12 h. The copper-EDTA complex was retained in 0.7 position from the anode after 12 h and, after 24 h, the position shifted to 0.8-0.9 from the anode. The possibility of accumulating metal ions within a narrow area, such as a pH junction was demonstrated.

Imaging of Jurassic fossils from the Talbragar Fish Bed using fluorescence, photoluminescence, and elemental and mineralogical mapping.

The Talbragar Fish Bed is one of Australia's most important Jurassic deposits for freshwater fishes, land plants and aquatic and terrestrial insects. The site has yielded many well preserved fossils, which has led to the formal description of numerous new species and higher taxa. The excellent preservation of many fossils has allowed detailed anatomical studies, e.g. of the early teleost fish Cavenderichthys talbragarensis (Woodward, 1895). Here we report on the fluorescent characteristics and mineral composition of a range of Talbragar fossils. Most specimens fluoresce under ultraviolet, blue and green light. Elemental and mineralogical analyses revealed that the Talbragar fossils consist predominantly of quartz (SiO2), a mineral that is likely to account for the observed fluorescence, with trace kaolinite (Al2Si2O5(OH)4) in some of the fish fossils. Rock matrices are predominantly composed of quartz and goethite (FeO(OH)). Closer inspection of a plant leaf (Pentoxylon australicum White, 1981) establishes fluorescence as a useful tool for the visualisation of anatomical details that are difficult to see under normal light conditions.

Comparison of electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially polluted soil.

Electrokinetic remediation methods for removal of heavy metals from polluted soils have been subjected for quite intense research during the past years since these methods are well suitable for fine-grained soils where other remediation methods fail. Electrodialytic remediation is an electrokinetic remediation method which is based on applying an electric dc field and the use of ion exchange membranes that ensures the main transport of heavy metals to be out of the pollutes soil. An experimental investigation was made with electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially polluted soil under the same operational conditions (constant current density 0.2 mA/cm(2) and duration 28 days). The results of the present paper show that caution must be taken when generalising results obtained in spiked kaolinite to remediation of industrially polluted soils, as it was shown that the removal rate was higher in kaolinite than in both spiked soil and industrial polluted soil. The duration of spiking was found to be an important factor too, when attempting to relate remediation of spiked soil or kaolinite to remediation of industrially polluted soils. Spiking for 2 days was too short. However, spiking for 30 days resulted in a pattern that was more similar to that of industrially polluted soils with similar compositions both regarding sequential extraction and electrodialytic remediation result, though the remediation still progressed slightly faster in the spiked soil. Generalisation of remediation results to a variety of soil types must on the other hand be done with caution since the remediation results of different industrially polluted soils were very different. In one soil a total of 76% Cu was removed and in another soil no Cu was removed only redistributed within the soil. The factor with the highest influence on removal success was soil pH, which must be low in order to mobilize Cu, and thus the buffering capacity against acidification was the key soil characteristics determining the Cu removal rate.

Adsorption behavior of strontium on binary mineral mixtures of montmorillonite and kaolinite.

The adsorption behavior of kaolinite and montmorillonite minerals and their mixtures in respect of Sr ion were studied by means of a batch method using (90)Sr as a radio tracer. The effect of several parameters such as temperature, pH, Sr concentration and supporting electrolyte were investigated. Experimentally measured distribution coefficients showed a good agreement to within 98.5-99.7% with theoretically calculated values. The values of adsorption capacity of adsorbents and mean adsorption energy of adsorption were calculated by fitting the adsorption data to Dubinin-Radushkevich isotherm. The adsorption capacity of clay mixtures decreased as kaolinite fractions increased. The mean adsorption energy values of 8.0-9.5 kJ mol(-1) showed that adsorption was governed by ion exchange. The Freundlich parameters were used to characterize a site distribution function for binary exchange between Sr and Na.