clay and goethite

Soil, composed mainly of minerals, plays a central role in the circulation of microbial pathogens in the environment. Herein, the growth, biofilm formation, and virulence gene expression of the pathogenic bacteria Escherichia coli O157:H7 were monitored following exposure to montmorillonite, kaolinite, and goethite, three common soil minerals in the clay size fraction. E. coli O157:H7 growth was notably promoted (P < 0.05), while biofilm formation was inhibited in the presence of montmorillonite (P < 0.05), which is attributed to the suppression of colanic acid (CA) production and an increase in bacterial motility. Kaolinite not only promoted bacterial growth (P < 0.05), but also contributed to biofilm formation upon stimulating CA production. Upon exposure to goethite, notably slower bacterial growth and higher biomass of biofilm were observed as compared to the control (P < 0.05). Goethite stimulated the synthesis of CA to encase cells in a protective biofilm in response to the tight association between bacteria and goethite, which could cause bacterial death. Additionally, the transcription of virulence factors (stxA-1 and stxA-2) was significantly decreased in goethite or kaolinite system (P < 0.05). These findings indicate that minerals play important roles in the physiological state of bacteria and ultimately govern the fate of this pathogen in soils.

Topics: Bentonite; Biofilms; Clay; Escherichia coli O157; Iron Compounds; Kaolin; Minerals; Soil; Virulence

Infiltration of heavy metal (HM) polluted wastewater can seriously compromise soil and groundwater quality. Interactions between mineral soil components (e.g. clay minerals) and dissolved organic matter (DOM) play a crucial role in determining HM mobility in soils. In this study, the influence of the timing of addition of DOM, i.e. concurrent with or prior to HMs, on HM mobility was explored in a set of continuous flow column experiments using well defined natural soil samples amended with goethite, birnessite and/or smectite. The soils were subjected to concurrent and sequential additions of solutions of DOM, and Cu, Ni and Zn. The resulting breakthrough curves were fitted with a modified dose-response model to obtain the adsorption capacity (q

Topics: Adsorption; Aluminum Silicates; Clay; Copper; Hydroxides; Ions; Iron Compounds; Kinetics; Minerals; Nickel; Organic Chemicals; Soil; Soil Pollutants; Wastewater; Water Pollutants, Chemical; Zinc

Reactive waste dumps with sulfide minerals promote acid mine drainage (AMD), which results in water and soil contamination by metals and metalloids. In these systems, contamination is regulated by many factors, such as mineralogical composition of soil and the presence of sorption sites on specific mineral phases. So, the present study dedicates itself to understanding the distribution of trace elements in different size fractions (<2-mm and <2-μm fractions) of mining soils and to evaluate the relationship between chemical and mineralogical composition. Cerdeirinha and Penedono, located in Portugal, were the waste dumps under study. The results revealed that the two waste dumps have high degree of contamination by metals and arsenic and that these elements are concentrated in the clay size fraction. Hence, the higher degree of contamination by toxic elements, especially arsenic in Penedono as well as the role of clay minerals, jarosite, and goethite in retaining trace elements has management implications. Such information must be carefully thought in the rehabilitation projects to be planned for both waste dumps.

Topics: Aluminum Silicates; Arsenic; Clay; Environmental Monitoring; Environmental Pollution; Ferric Compounds; Iron Compounds; Metalloids; Metals; Minerals; Mining; Portugal; Soil; Soil Pollutants; Sulfates; Sulfides; Trace Elements; Waste Disposal Facilities

Archaeological indicators of cognitively modern behaviour become increasingly prevalent during the African Middle Stone Age (MSA). Although the exploitation of ochre is viewed as a key feature of the emergence of modern human behaviour, the uses to which ochre and ochre-based mixtures were put remain ambiguous. Here we present the results of an experimental study exploring the efficacy of ochre as a topical photoprotective compound. This is achieved through the in vivo calculation of the sun protection factor (SPF) values of ochre samples obtained from Ovahimba women (Kunene Region, Northern Namibia) and the Palaeozoic Bokkeveld Group deposits of the Cape Supergroup (Western Cape Province, South Africa). We employ visible spectroscopy, energy-dispersive X-ray fluorescence (ED-XRF), X-ray diffraction (XRD) and granulometric analyses to characterise ochre samples. The capacity of ochre to inhibit the susceptibility of humans to the harmful effects of exposure to ultraviolet radiation (UVR) is confirmed and the mechanisms implicated in the efficacy of ochre as a sunscreen identified. It is posited that the habitual application of ochre may have represented a crucial innovation for MSA humans by limiting the adverse effects of ultraviolet exposure. This may have facilitated the colonisation of geographic regions largely unfavourable to the constitutive skin colour of newly arriving populations.

Topics: Aluminum Silicates; Animals; Butter; Clay; Cosmic Radiation; Earth, Planet; Extinction, Biological; Female; Ferric Compounds; History, 21st Century; History, Ancient; Hominidae; Human Migration; Humans; Iron Compounds; Magnetic Fields; Male; Minerals; Namibia; Ointments; Particle Size; Quartz; Selection, Genetic; Skin; Skin Pigmentation; Soil; Spectrometry, X-Ray Emission; Spectrophotometry; Sun Protection Factor; Sunlight; Sunscreening Agents; Ultraviolet Rays; X-Ray Diffraction

Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of -3.0 ± 0.4 nN and -330 ± 43 aJ (10(-18) J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions.

Topics: Agrobacterium tumefaciens; Aluminum Silicates; Bacillus subtilis; Bacterial Adhesion; Biofilms; Clay; Escherichia coli; Iron Compounds; Microscopy, Atomic Force; Microscopy, Electron, Scanning; Minerals; Particle Size; Pseudomonas putida; Surface Properties; Thermodynamics; Time Factors

The photochemical behavior of the pesticide azinphos methyl at the surface of clays (kaolinite, bentonite) and goethite was studied using Suntest setup (λ > 300 nm). The quantum yield on the clays was found to be roughly three times lower than that in aqueous solution. However, the photochemical efficiency was much higher at the surface of goethite owing to its photocatalytic activity through the hydroxyl radical production. The added humic substances on kaolonite show an inhibition of azinphos methyl degradation while the incorporation of iron(III) aquacomplexes leads to an important increase of the disappearance together with the formation of iron(II). Hydroxyl radical species were found to be formed either by excitation of goethite or clays. The goethite support acts as a more efficient catalyst for the formation of these reactive oxygen species. The photodecomposition reactions observed were (i) hydrolysis process leading to the formation of benzotriazone and the oxidation of the P = S bond giving rise to the formation of the oxon derivative, and (ii) homolytic cleavage of the N-C and C-S bonds of the organophosphorus bridge leading to the formation of dimers that appear to be specific to the irradiation at the surface of solid supports since they were not observed when the irradiation was performed in aqueous media: a statement that is related to the presence of aggregates at the surface of solid supports.

Topics: Aluminum Silicates; Azinphosmethyl; Catalysis; Clay; Humic Substances; Hydroxyl Radical; Iron Compounds; Minerals; Oxidation-Reduction; Pesticides; Photolysis; Sunlight; Surface Properties

The adsorption of extracellular polymeric substances (EPS) from Bacillus subtilis on montmorillonite, kaolinite and goethite was investigated as a function of pH and ionic strength using batch studies coupled with Fourier transform infrared (FTIR) spectroscopy. The adsorption isotherms of EPS on minerals conformed to the Langmuir equation. The amount of EPS-C and -N adsorbed followed the sequence of montmorillonite>goethite>kaolinite. However, EPS-P adsorption was in the order of goethite>montmorillonite>kaolinite. A marked decrease in the mass fraction of EPS adsorption on minerals was observed with the increase of final pH from 3.1 to 8.3. Calcium ion was more efficient than sodium ion in promoting EPS adsorption on minerals. At various pH values and ionic strength, the mass fraction of EPS-N was higher than those of EPS-C and -P on montmorillonite and kaolinite, while the mass fraction of EPS-P was the highest on goethite. These results suggest that proteinaceous constituents were adsorbed preferentially on montmorillonite and kaolinite, and phosphorylated macromolecules were absorbed preferentially on goethite. Adsorption of EPS on clay minerals resulted in obvious shifts of infrared absorption bands of adsorbed water molecules, showing the importance of hydrogen bonding in EPS adsorption. The highest K values in equilibrium adsorption and FTIR are consistent with ligand exchange of EPS phosphate groups for goethite surface. The information obtained is of fundamental significance for understanding interfacial reactions between microorganisms and minerals.

Topics: Adsorption; Aluminum Silicates; Bacillus subtilis; Bentonite; Biopolymers; Carbon; Clay; Extracellular Space; Ferric Compounds; Hydrogen-Ion Concentration; Iron Compounds; Kaolin; Minerals; Nitrogen; Osmolar Concentration; Phosphorus; Spectroscopy, Fourier Transform Infrared; Temperature

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.

Topics: Aluminum Silicates; Chromium; Clay; Environmental Monitoring; Filtration; Groundwater; Iron Compounds; Minerals; Oklahoma; Soil; Soil Pollutants; Water Pollutants, Chemical; X-Ray Diffraction

Bacterial-mineral composites are important in the retention of heavy metals due to their large sorption capacity under a wide range of environmental conditions. This study provides the first quantitative comparison of the metal-binding capacities of P. putida CZ1-goethite composite to its individual components. When the same amount (on a dry weight basis) of living and nonliving cells of P. putida CZ1, goethite or their composites was separately exposed to solutions of 0.5 mM Cu(II) and Zn(II) in 0.01 M KNO(3), the living cells removed the largest quantity of heavy metals. The results of calculated metal retention values indicated that the adsorption of goethite to bacteria has not mask or neutralize chemically reactive adsorption sites normally available to metal ions. Moreover, the nonliving cells-goethite composite retained approximately 82% more Zn than that predicted by their individual behavior. The preferential association of Zn with P. putida CZ1 was observed by TEM and EDS analyses of a mixture consisting of the bacteria and goethite. Desorption of Cu and Zn with 1.0M CH(3)COOK solution from P. putida CZ1 and goethite indicated the differences in the functional groups able to bind heavy metals.

Topics: Adsorption; Aluminum Silicates; Clay; Environmental Restoration and Remediation; Iron Compounds; Metals, Heavy; Microbial Viability; Minerals; Pseudomonas putida; Solutions

Adsorption of Pseudomonas putida on minerals including montmorillonite, kaolinite and goethite was studied. The adsorption isotherms of P. putida on the examined minerals conformed to the Langmuir equation. The amount of P. putida adsorbed followed the order: goethite > kaolinite > montmorillonite. A greater extent of P. putida adsorption on minerals was observed in the range of temperature from 15 to 35 degrees C. The adsorption of P. putida on minerals decreased with the increase of pH from 3.0 to 10.0. Magnesium ion was more efficient than sodium ion in promoting P. putida adsorption on minerals. The results suggest that electrostatic interactions play a vital role in P. putida adsorption by soil colloidal factions. The information obtained in this study is of fundamental significance for the understanding of the survival and transport of bacteria in soil systems.

Topics: Adsorption; Aluminum Silicates; Bacterial Proteins; Bentonite; Clay; Ferric Compounds; Iron Compounds; Kaolin; Minerals; Pseudomonas putida

Polymerase chain reaction (PCR) was used to amplify a 600-base pair (bp) sequence of plasmid pGEX-2T DNA bound on soil colloidal particles from Brown soil (Alfisol) and Red soil (Ultisol), and three different minerals (goethite, kaolinite, montmorillonite). DNA bound on soil colloids, kaolinite, and montmorillonite was not amplified when the complexes were used directly but amplification occurred when the soil colloid or kaolinite-DNA complex was diluted, 10- and 20-fold. The montmorillonite-DNA complex required at least 100-fold dilution before amplification could be detected. DNA bound on goethite was amplified irrespective of whether the complex was used directly, or diluted 10- and 20-fold. The amplification of mineral-bound plasmid DNA by PCR is, therefore, markedly influenced by the type and concentration of minerals used. This information is of fundamental importance to soil molecular microbial ecology with particular reference to monitoring the fate of genetically engineered microorganisms and their recombinant DNA in soil environments.

Topics: Aluminum Silicates; Animals; Bentonite; Cattle; Clay; Colloids; DNA, Bacterial; Iron Compounds; Kaolin; Minerals; Plasmids; Polymerase Chain Reaction; Soil

The sorption interactions of oxytetracycline with goethite, hematite, and two iron oxide-rich soils were investigated using batch sorption experiments. Oxytetracycline sorption coefficients for goethite and hematite increased with pH to maximum values at pH approximately 8. The sorption edge shape and desorption treatments were consistent with a surface complexation mechanism and could be described by the interaction of divalent anion species with the oxide surface. Oxytetracycline sorption to Georgeville and Orangeburg Ultisol soils decreased with pH. Chemical digestion treatments were used to deduce that soil sorption occurred by complexation to oxide coatings on clay and quartz grains. These results indicate that sorption models must consider the interaction of oxytetracycline, and other similar ionogenic compounds, with soil oxide components in addition to clays and organic matter when predicting sorption in whole soils.

Topics: Adsorption; Aluminum Silicates; Clay; Ferric Compounds; Hydrogen-Ion Concentration; Iron Compounds; Minerals; Organic Chemicals; Oxytetracycline; Soil; Soil Pollutants; Surface Properties; Water Pollutants

Adsorption, desorption and activity of acid phosphatase on various soil colloidal particles and pure clay minerals were studied. Higher adsorption amounts and low percentage of desorption of acid phosphatase were found on fine soil clays (<0.2 microm). Electrostatic force and ligand exchange are the major driving forces that are involved in the adsorption of enzymes on soil clays. More enzyme molecules were adsorbed on soil clays in the presence of organic components. However, enzymes on organic clays were more easily released. One-third of the enzyme on goethite was adsorbed via ligand exchange process. Some other interactions, such as van der Waals force, hydrophobic force and hydrogen bonding may be more important in the adsorption of enzyme on kaolinite and the enzyme in this system cannot be easily removed. Coarse clays (0.2-2 microm) and inorganic soil clays had higher affinities for enzyme molecules than fine clays and organic clays, respectively. The activity of enzyme bound on soil clays was inhibited and the thermal stability was increased in the presence of organic matter. Data obtained in this study are helpful for a better understanding of the interactions of enzymes with inorganic and organic constituents in soil and associated environments.

Topics: Acid Phosphatase; Adsorption; Aluminum Silicates; Clay; Colloids; Hydrogen-Ion Concentration; Iron Compounds; Kaolin; Ligands; Minerals; Particle Size; Sensitivity and Specificity; Soil; Surface Properties; Temperature