I. González

Heavy metal partitioning in river sediments severely polluted by acid mine drainage in the Iberian Pyrite Belt

This study provides a geochemical partitioning pattern of Fe, Mn and potentially toxic trace elements (As, Cd, Cr, Cu, Ni, Pb, Zn) in sediments historically contaminated with acid mine drainage, as determined by using a 4-step sequential extraction scheme. At the upperstream, the sediments occur as ochreous precipitates consisting of amorphous or poorly crystalline oxy-hydroxides of Fe, and locally jarosite, whereas the estuarine sediments are composed mainly of detrital quartz, illite, kaolinite, feldspars, carbonates and heavy minerals, with minor authigenic phases (gypsum, vivianite, halite, pyrite). The sediments are severely contaminated with As, Cd, Cu, Pb and Zn, especially in the vicinity of the mining pollution sources and some sites of the estuary, where the metal concentrations are several orders of magnitude above background levels. Although a significant proportion of Zn, Cd and Cu is present in a readily soluble form, the majority of heavy metals are bonded to reducible phases, suggesting that Fe oxy-hydroxides have a dominant role in the metal accumulation. In the estuary, the sediments are potentially less reactive than in the riverine environment, because relevant concentrations of heavy metals are immobilised in the crystalline structure of minerals.

Residual pollution load of soils impacted by the Aznalcóllar (Spain) mining spill after clean-up operations

By comparing total concentrations of potentially toxic elements in soils affected by the Aznalcóllar mining spill with those of the adjacent unaffected soils, it can be inferred that after the sludge removal, there still exists a considerable amount of residual pollution. This exceeds the suitable levels for cultivation, especially in the case of arsenic for which total concentrations are in the range of values above which eco-toxicity is considered to be possible. Elemental distribution in the soil seems to be determined by two distinctive associations (As-Pb-Hg-Sb and Cu-Zn-Cd) with different geochemical behaviours.

Contribution of mine wastes to atmospheric metal deposition in the surrounding area of an abandoned heavily polluted mining district (Rio Tinto mines, Spain)

The present study seeks to estimate the impact of abandoned mine wastes on the levels and chemical profile of total atmospheric deposition in one of the oldest and largest mining districts in Europe (Rio Tinto mines, Iberian Pyrite Belt), on the basis of a complete geochemical characterization of particulate matter samples periodically collected in five sampling stations located around the mining district between March 2009 and February 2011. The annual levels of total bulk deposition (soluble and insoluble fractions) registered in the Rio Tinto Mining District ranged between 18 and 43 g/m(2) depending on the distance from the sampling station with regard to the mine waste deposits. As a general pattern in the area, high mass levels of Zn and Cu were deposited in a range of 9-62 mg/m(2) not only in the insoluble but also in the soluble fraction. Other potentially toxic trace elements such as As, Sb, Ba, Pb, Sn and Bi showed greater deposition fluxes in the locations closest to the mine waste deposits. A principal component analysis with a Multilinear Regression Analysis certifies the presence of two common sources in the mining area: 1) a mineral factor composed mainly of elements derived from silicate minerals (Al, Ca, Sr, Ti, Li, Mg, Mn, K, Na and Fe), mixed with other anthropogenic species (NH4(+), SO4(2-), NO3(-)) within the village closest to the mine; and 2) a marine factor composed of Na, Cl, Mg, SO4(2-) and Sr. In addition, a mine waste factor made up of toxic elements (Cu, Zn, Ga, As, Sb, Ba, Pb, Sn, Cd and Bi) has been recognized in the sampling sites exposed to dust-bearing winds downwind of the mining area, suggesting that mine wastes are a relevant source of heavy-mineral particles with potentially adverse environmental effects to surrounding soils, plants and humans.

Pyridoxal 5′-Phosphate Is a Slow Tight Binding Inhibitor of E. coli Pyridoxal Kinase

Pyridoxal 5′-phosphate (PLP) is a cofactor for dozens of B6 requiring enzymes. PLP reacts with apo-B6 enzymes by forming an aldimine linkage with the ε-amino group of an active site lysine residue, thus yielding the catalytically active holo-B6 enzyme. During protein turnover, the PLP is salvaged by first converting it to pyridoxal by a phosphatase and then back to PLP by pyridoxal kinase. Nonetheless, PLP poses a potential toxicity problem for the cell since its reactive 4′-aldehyde moiety forms covalent adducts with other compounds and non-B6 proteins containing thiol or amino groups. The regulation of PLP homeostasis in the cell is thus an important, yet unresolved issue. In this report, using site-directed mutagenesis, kinetic, spectroscopic and chromatographic studies we show that pyridoxal kinase from E. coli forms a complex with the product PLP to form an inactive enzyme complex. Evidence is presented that, in the inhibited complex, PLP has formed an aldimine bond with an active site lysine residue during catalytic turnover. The rate of dissociation of PLP from the complex is very slow, being only partially released after a 2-hour incubation with PLP phosphatase. Interestingly, the inactive pyridoxal kinase•PLP complex can be partially reactivated by transferring the tightly bound PLP to an apo-B6 enzyme. These results open new perspectives on the mechanism of regulation and role of pyridoxal kinase in the Escherichia coli cell.

Geology, mineralogy, origin and possible applications of some Argentinian kaolins in the Neuquen basin

Abstract The geology and genesis of three kaolin deposits (Las Mellizas, Chita and Misud), located in the Neuquen basin were studied. Kaolin mineralogy and oxygen isotopic data indicate that kaolinite comes from a weathered area developed during the lower to middle Jurassic times; the kaolinite was then transported and deposited in a fluvial environment. I/Sm comes from in situ illite degradation. Kaolin properties are related to mineralogical and chemical composition and to compactation and cementation. Low plasticity of these kaolins is due to high degrees of compactation undergone, and plasticity increases as I/Sm content increases. Viscosity is related to pH: in low pH clay suspensions the edge faces are positively charged, so on stirring, they collide with the negative charged faces forming card-house structures, thus enhancing the viscosity. Cementation effects makes it difficult to get dispersed suspensions. As a ceramic raw material, these kaolins are considered stoneware clays. When kaolins with lower iron oxide content are mixed with quartz and feldspar, an optimum white stoneware is obtained at 1150°C. On this basis, the three deposits can be exploited to make stoneware products, but selected beds should be mined in order to obtain the best quality.

Properties and applications of diatomitic materials from SW Spain

Abstract Diatomaceous materials (diatomites and diatomitic marls) from the Guadalquivir basin (SW Spain) were characterized mineralogically, physically and physico-chemically. Some potential uses for these materials are suggested based on the results obtained, as well as on laboratory beneficiation tests and applicable specifications. The diatomitic materials are of only fair quality, but, upon appropriate treatment, can be used as catalyst supports, filter aids and lightweight structural ceramic bodies. In addition, the marls can be used for industrial ceramic purposes as constituents of structural clay products to be fired at temperatures between 900 and 1000°C.

A proposal for reducing F and Cl emission in the brick industry using new formulations

Abstract Emissions of F and Cl by the brick and tile industry of Bailen (Jaen, Spain) can be reduced by preparing mixtures of the three clays traditionally used in that area (white, and blonde Tertiary loams and Triassic red loam), which F content ranges between 850 and 1200 ppm, with an Al-rich clay of low F content ( 30% because its higher F initial content and its lower proportion of carbonate produce higher emissions. For Cl, the initial content is very low (

Stabilization of fly ash using cementing bacteria. Assessment of cementation and trace element mobilization

Fly ash from municipal solid waste incineration (MSWI) was treated with microorganisms (Sporosarcina pasteurii and Myxococcus xanthus) to assess their capacity for cementing this waste material. Leaching tests on the samples treated with bacteria were also performed to assess the possibility of recovering and recycling trace elements from the fly ash. Sequential extractions combined with mineralogical studies demonstrated that Pb is mobile in water when associated with portlandite. Also, Cd, Pb, and Zn are primarily associated with carbonates and are mobile in acidic environments (up to 4.8, 13.9 and 248mg/l of Cd, Pb and Zn, respectively, extracted with acetic acid). Microbial treatment of the fly ash, especially with Sporosarcina pasteurii, led to its cementation and stabilization, preventing its dispersion into the environment. But samples treated with bacteria exhibited a higher capacity for trace element leaching than did untreated fly ash. The ability of these bacteria to mobilize metals can be applied to recover those of economic interest. The use of low cost biotechnologies can be an alternative to chemical treatments currently utilized for the recovery and reuse of these wastes.

A methodological approach to estimate the geogenic contribution in soils potentially polluted by trace elements. Application to a case study

PurposeThe determination of the contribution of background values in a potentially polluted soil is very important in defining the contamination extension, in particular in areas of geological complexity and long-term economic development, where mining and industry have been traditional activities and soils are showing both geogenic and anthropogenic contributions. Some approaches have been proposed for the estimation of the anthropogenic input vs. the background; in this paper we present a more robust approach.Materials and methodsThe proposed methodological approach includes the following steps. The first step consists of the comparison among the trace element contents in potentially polluted soils (PPS) and the reference and threshold values calculated both for the same geotectonic unit. A second stage is the calculation of the reference and threshold values for the surrounding area (LTV), natural setting, of the PPS with similar lithological characteristics. The final step is based on the analysis of the results by comparison of the PPS with LTV. On the other hand, the definition of a new pollution factor allows to grade the pollution and to classify the pollution importance.Results and discussionThe protocol proposed was applied to PPS from a potentially polluted area of SW Spain. The anthropogenic vs. geogenic anomalies and the pollution grade of the three PPS were assessed, which is important to establish the priority to further actions. In addition, this study makes clear that the use of the enrichment factors to estimate the pollution of soils is not advisable. On the other hand, in this study, new areas close to the PPS were defined as potentially polluted because of the high trace element concentration.ConclusionsThe methodological approach proposed can be considered as a good indicator for evaluating the geogenic vs. anthropogenic contribution in polluted soils and for classifying the pollution importance in a more robust way than the use of other previous indexes. The proposal methodology could be used also by the administration to detect other PPS in a study area, which a priori were not considered as contaminated.

The effect of pressure on order/disorder in kaolinite under wet and dry conditions

Well ordered kaolinite was isostatically and uniaxially pressurized up to 13,200 kg/cm2 for 10 min in dry conditions and the effects of pressure on kaolinite order were determined by analyzing the shapes of two-dimensional diffraction bands on X-ray powder diffraction patterns. Increased pressure decreased the percentage of low-defect kaolinite phase, and isostatic pressure proved to be more effective than uniaxial pressure in increasing disorder, e.g. the degree of disorder resulting from 2000 kg/cm2 isostatic pressure was equivalent to that caused by a 3200 kg/cm2 uniaxial pressure. Also, the effect of high pressure was similar to that obtained with lower pressures applied several times (e.g. the effect of applying 8500 kg/cm2 pressure for 10 min was comparable to using 3200 kg/cm2 pressure five times).In addition, six kaolinites of different structural order were isostatically pressurized up to 4000 kg/cm2 for 10 min, both in dry and wet (water) conditions. Under dry conditions, changes in structurally ordered kaolinite were comparable to those cited above whereas kaolinite pressurized in wet conditions showed a moderate improvement in structural order.These results may contribute to our understanding of kaolinite behavior during burial diagenesis and low-grade metamorphism. In addition, these results can also be used in industry to improve kaolin technological properties that depend on kaolinite structural order by application of appropriate industrial pressure processes.