Metal/metalloid contamination and isotopic composition of lead in edible mushrooms and forest soils originating from a smelting area

High metal contents in edible mushrooms growing in severely contaminated industrial areas pose an important toxicological risk. In the presented study, trace element (Pb, Cd, Zn, Cu, Ag, As, Se) contents were determined in caps and stipes of three different edible mushroom species (Boletus edulis Bull. Fr., Xerocomus badius Fr. Gilb., Xerocomus chrysenteron Bull. Quél.). Additionally, information about the chemical fractionation of metals in separate soil horizons and Pb isotopic data from soils and fruiting bodies allowed a more detailed insight on the uptake mechanisms of metals by the studied mushroom species. Total metal and metalloid concentrations in the organic soil horizons reached 36234 mg Pb kg(-1); 11.9 mg Cd kg(-1); 519 mg Zn kg(-1); 488 mg Cu kg(-1); 25.1 mg Ag kg(-1); 120 mg As kg(-1) and 5.88 Se mg kg(-1). In order to evaluate the accumulation capacity of the studied species, bioconcentration factors (BCF) were calculated for separate trace elements. For selected metals (Pb, Cd, Zn, Cu), a modified BCF calculation (using EDTA-extractable concentrations of metals in soil) was proposed. High contents of Pb (up to 165 mg kg(-1)) and Cd (up to 55 mg kg(-1)) exceeded all the regulatory limits in all the studied species. This was also the case for Se (up to 57 mg kg(-1)) in B. edulis. Intensive consumption of this species grown in such polluted areas can therefore pose toxicological risks for human health. A novel finding was that X. badius can act as an Ag accumulating species when grown at polluted sites due to the high concentrations of Ag (up to 190 mg kg(-1)) in caps. Pb isotopic data showed that Pb originating from the recent air pollution control residues is present mainly in the exchangeable/acid-extractable fraction of the organic horizons and is taken up by fruiting bodies; especially in the case of B. edulis, where fast Pb accumulation occurs. Due to the high species-dependent variations of metal contents, the studied mushrooms are not suitable as bioindicators of environmental pollution.     

Expedient Metrics to Describe Plant Community Change Across Gradients of Anthropogenic Influence

Human influence associated with land use may cause considerable biodiversity losses, namely in oceanic islands such as the Azores. Our goal was to identify plant indicator species across two gradients of increasing anthropogenic influence and management (arborescent and herbaceous communities) and determine similarity between plant communities of uncategorized vegetation plots to those in reference gradients using metrics derived from R programming. We intend to test and provide an expedient way to determine the conservation value of a given uncategorized vegetation plot based on the number of native, endemic, introduced, and invasive indicator species present. Using the metric IndVal, plant taxa with a significant indicator value for each community type in the two anthropogenic gradients were determined. A new metric, ComVal, was developed to assess the similarity of an uncategorized vegetation plot toward a reference community type, based on (i) the percentage of pre-defined indicator species from reference communities present in the vegetation plots, and (ii) the percentage of indicator species, specific to a given reference community type, present in the vegetation plot. Using a data resampling approach, the communities were randomly used as training or validation sets to classify vegetation plots based on ComVal. The percentage match with reference community types ranged from 77 to 100 % and from 79 to 100 %, for herbaceous and arborescent vegetation plots, respectively. Both IndVal and ComVal are part of a suite of useful tools characterizing plant communities and plant community change along gradients of anthropogenic influence without a priori knowledge of their biology and ecology.     

Evaluation of different amendments to stabilize antimony in mining polluted soils

Soil pollution with antimony is of increasing environmental concern worldwide. Measures for its control and to attenuate the risks posed to the ecosystem are required. In this study the application of several iron and aluminium oxides and oxyhydroxides as soil amendments was evaluated in order to assess their feasibility to stabilize Sb in mining polluted soils. Mine soils with different pollution levels were amended with either goethite, ferrihydrite or amorphous Al oxide at various ratios (0–10%). The effectiveness of such treatments was assessed by both batch and column leaching tests. The use of ferrihydrite or amorphous Al oxide proved to be highly effective to stabilize Sb. Immobilization levels of 100% were found when doses of 5% ferrihydrite or 10% amorphous Al oxide were applied, regardless of the soil Sb load. Column leaching studies also showed a high Sb leaching reduction (>75%) when soils were amended with 1% ferrihydrite or 5% amorphous Al oxide. Moreover, such treatments proved to simultaneously immobilize As and Pb in a great extent when soils were also polluted with such toxic elements.     

Mineralization of integrated gasification combined-cycle power-station wastewater effluent by a photo-fenton process

The aim of this work was to study the mineralization of wastewater effluent from an integrated-gasification combined-cycle (IGCC) power station sited in Spain to meet the requirements of future environmental legislation. This study was done in a pilot plant using a homogeneous photo-Fenton oxidation process with continuous addition of H₂O₂ and air to the system.The mineralization process was found to follow pseudo-first-order kinetics. Experimental kinetic constants were fitted using neural networks (NNs). The NNs model reproduced the experimental data to within a 90% confidence level and allowed the simulation of the process for any values of the parameters within the experimental range studied. At the optimum conditions (H₂O₂ flow rate = 120 mL/h, [Fe(II)] = 7.6 mg/L, pH = 3.75 and air flow rate = 1 m³/h), a 90% mineralization was achieved in 150 min.Determination of the hydrogen peroxide consumed and remaining in the water revealed that 1.2 mol of H₂O₂ was consumed per each mol of total organic carbon removed from solution. This result confirmed that an excess of dissolved H₂O₂ was needed to achieve high mineralization rates, so continuous addition of peroxide is recommended for industrial application of this process.Air flow slightly improved the mineralization rate due to the formation of peroxo-organic radicals which enhanced the oxidation process.     

Use of coatings to minimise acid emissions during ceramic tile firing

The manufacture of traditional ceramic products (ceramic tiles, roof tiles, and bricks) is often associated with the emission of F, Cl, and S compounds during the firing stage. According to the literature, fluorine emissions can be reduced by adding CaCO₃ to the raw materials mixture used in fabricating these products. However, data available to the authors indicate that this procedure, which has been successfully applied in manufacturing structural ceramics (roof tiles and bricks), is ineffective in ceramic tile manufacture and modifies tile end properties.This paper examines the possibility of reducing such emissions by applying coatings of alkaline-earth carbonates on to the ceramic tile bottom surface to retain the acid compounds emitted during tile firing. The effectiveness of MgCO₃, CaCO₃, SrCO₃, and BaCO₃ coatings for retaining these acid emissions was studied, using the evolved gas analysis (EGA) technique with a TG-DSC-FTIR-QM instrument.The SrCO₃ coating was found to provide the greatest retention, showing that SO₂ and HCl were retained more efficiently than HF. The presence of fluorides, chlorides, and sulphates of Ca, Sr, and Ba was verified in the respective fired coatings, confirming the existence of chemical reactions between the emitted acid compounds and the coating materials at high temperature.     

The role of wax and resin in the nestmate recognition system of a stingless bee, Tetragonisca angustula

Recent research has shown that entrance guards of the stingless bee Tetragonisca angustula make less errors in distinguishing nestmates from non-nestmates than all other bee species studied to date, but how they achieve this is unknown. We performed four experiments to investigate nestmate recognition by entrance guards in T. angustula. We first investigated the effect of colony odours on acceptance. Nestmates that acquired odour from non-nestmate workers were 63% more likely to be rejected while the acceptance rate of non-nestmates treated with nestmate odour increased by only 7%. We further hypothesised that guards standing on the wax entrance tube might use the tube as an odour referent. However, our findings showed that there was no difference in the acceptance of non-nestmates by guards standing on their own colony’s entrance tube versus the non-nestmate’s entrance tube. Moreover, treatment of bees with nestmate and non-nestmate resin or wax had a negative effect on acceptance rates of up to 65%, regardless of the origin of the wax or resin. The role of resin as a source of recognition cues was further investigated by unidirectionally transferring resin stores between colonies. Acceptance rates of nestmates declined by 37% for hives that donated resin, contrasting with resin donor hives where acceptance of non-nestmates increased by 21%. Overall, our results confirm the accuracy of nestmate recognition in T. angustula and reject the hypothesis that this high level of accuracy is due to the use of the wax entrance tubes as a referent for colony odour. Our findings also suggest that odours directly acquired from resin serve no primary function as nestmate recognition cues. The lack of consistency among colonies plus the complex results of the third and fourth experiments highlight the need for further research on the role of nest materials and cuticular profiles in understanding nestmate recognition in T. angustula.     

Atmospherically deposited major and trace elements in the winter snowpack along a gradient of altitude in the Central Pyrenees: The seasonal record of long-range fluxes over SW Europe

The chemistry of high mountain snowpacks is a result of the long-range atmospheric transport and deposition of elements. Pyrenean snowpacks contain information about the fluxes of elements over SW Europe in winter. Here we analysed Al, Ti, Mn, Fe, Ni, Cu, Zn, As, Se, Cd and Pb in the 2004–05 winter snowpack in the Central Pyrenees, at an altitude range of 1820–3200 m a.s.l. Ni, As, Se and Cd were not detected in most cases. The concentrations of the remaining elements were comparable to those found in other high mountain areas in Europe and North America considered representative of regional background of atmospheric deposition in populated areas. In contrast, our measurements were higher than those of polar areas, which represent the global background. Single measurements of concentrations and snow accumulation were subject to considerable spatial variability, which may be attributable to strong wind drift and other post-depositional processes. The major ions chemistry of the snow indicated three possible origins for the solutes: terrigenous dust, sea salt spray and polluting S and N aerosols. We found no association between Cu, Zn and Pb and any of these possible sources. This observation therefore indicates that these elements were not preferentially bound to any particular kind of aerosol. Snow collected at altitudes of up to 2050 m a.s.l. presented higher concentrations of several elements than snow above this altitude, thereby indicating a local influence. Snow collected above 2300 m a.s.l. was therefore more representative of broad regional inputs. At these higher altitudes, snow was not enriched in Al, Ti, Mn, Fe or As compared with the composition of the upper continental crust and the local lithology, and these elements (except Mn) appeared almost exclusively in the particulate fraction. This observation indicates that Al, Ti, Mn, Fe and As were present mainly as part of dust particles of terrigenous origin. In contrast, Cu, Zn, and Pb presented medium to high enrichment factors and showed a higher proportion of soluble forms, thereby indicating their polluting character.     

Evaluation of Saccharomyces cerevisiae strains as probiotic agent with aflatoxin B1 adsorption ability for use in poultry feedstuffs

In this study the aflatoxin B₁ (AFB₁) removal capacity, the tolerance to salivary and gastrointestinal conditions, autoaggregation and coaggregation with pathogenic bacteria of Saccharomyces cerevisiae strains isolated from broiler feces, were evaluated. Only four of twelve isolated strains were identified as Saccharomyces cerevisiae using molecular techniques. The results obtained in AFB₁ binding studies indicated that the amount of AFB₁ removed was both strain and mycotoxin-concentration dependent. Therefore, a theoretical model was applied in order to select the most efficient strain to remove AFB₁ in a wide range of mycotoxin concentration. The results indicated that S. cerevisiae 08 and S. cerevisiae 01 strains were the most efficient microorganisms in the mycotoxin removal. Viability on simulated salivary and gastrointestinal conditions was investigated and S. cerevisiae 08 strain showed the best results, achieving 98% of total survival whereas S. cerevisiae 01 reached only 75%. Autoaggregation and coaggregation assays showed S. cerevisiae 08 as the most appropriate strain, mainly because it was the unique strain able to coaggregate with the four bacterial pathogens assayed. Consequently, S. cerevisiae 08 is the best candidate for future in vivo studies useful to prevent aflatoxicosis. Further quantitative in vitro and in vivo studies are required to evaluate the real impact of yeast-binding activity on the bioavailability of AFB₁ in poultry. However, this study could be useful in selecting efficient strains in terms of AFB₁ binding and provide an important contribution to research into microorganisms with potential probiotic effects on the host.     

Homogenous catalyzed ozonation of simazine. Effect of Mn(II) and Fe(II).

Simazine, [2-chloro, 4,6-bis(ethylamino)-1,3,5-s-triazine], a common herbicide typically found in surface and ground water was ozonised by using catalytic amounts of Mn(II) and Fe(II). An optimum value for metal concentration was found in the process. Some inhibition of the simazine degradation rate was observed when these metals were added above the optimum concentration. The pH of the reaction media played a significant role in the simazine oxidation rate. Thus, an increase in simazine conversion was observed when the pH was raised from 5 to 9. However, the catalytic effect of added manganese was negligible at the highest pH used in this study (pH 9). The beneficial influence of Fe(II) was also observed when utilising the combination of ozone and hydrogen peroxide. Contrarily, Mn(II) presented a negative influence on simazine conversion when using this oxidation technology.