Efficient use of Fe metal as an electron transfer agent in a heterogeneous Fenton system based on Fe0/Fe3O4 composites

In this work a novel heterogeneous Fenton system based on Fe(0)/Fe3O4 composites is described. The composites with several Fe(0)/Fe3O4 ratios were prepared by two different methods, i.e. mechanical alloying of Fe(0) and Fe3O4 powders and controlled reduction of Fe3O4 with H2. Reaction studies and detailed Conversion Electron M?ssbauer surface characterization of the composites Fe(0)/Fe3O4, Fe(0), Fe3O4, alpha-Fe2O3 and gamma-Fe2O3 suggested that Fe2+surf species are essential to produce an active Fenton system. Kinetic studies for the oxidation of the dye methylene blue, used as an organic model molecule, and for the peroxide decomposition suggest that the reactions proceed via HO* radicals generated from Fe2+surf species and H2O2 in a Fenton like mechanism. The increase in activity caused by the addition of Fe(0) is discussed in terms of a creation of Fe2+surf species during the preparation of the composite and by an electron transfer mechanism from Fe(0) to Fe3+surf during the Fenton reaction to regenerate the Fe2+surf active species.     

Mercury exposure through diet in pregnant women and women of childbearing age

The study examined the stage of clean-up of the Port Lavaca bay sites in Texas, which were polluted during the early 1990's by effluent containing mercury (Hg) from a chloralkali plant. In addition to Hg intoxication through environmental contaminations, human exposure through dietary fish and other seafoods occurred. Bacteria converts inorganic Hg to alkyl organic compounds and subsequently the metal crosses the blood brain barrier thus exerting adverse effects on the fetal developing nervous system. In order to conduct a survey of dietary Hg exposure, blood was collected from pregnant women and those of childbearing age at routine clinic visits at each of three centers in South Texas cities (Galveston, Texas City, Port Lavaca/Victoria, TX). A questionnaire sought dietary and lifestyle information including consumption, sources of fish and other seafoods. A significant number of subjects (119 out of 175, 68%) ate fish caught locally. The blood Hg concentrations (µg?L^?1) range varied with the location of the study centers: City of Galveston 2.6–62; Texas City 2.8–111.8; and the Port Lavaca areas 3.02–126.7. The concentrations of blood Hg was directly proportional to the number of fish meals consumed for each species considered. Mean blood Hg concentrations for no fish meals per week were: Port Lavaca 4.5 (N?=?3), Galveston 4.3 (N?=?3), Texas City 3.5 (N?=?10). For >3 fish meals per week, the mean blood Hg concentrations were: Port Lavaca, 48.0 (N?=?53), Galveston 29.1 (N?=?35), Texas City, 36.1 (N?=?31). Data show that residues of Hg were still present in 1994 despite the clean-up efforts.     

Uptake and genotoxicity of micromolar concentrations of cobalt chloride in mammalian cells

Literature data concerning the genotoxicity of cobalt salts have been conflicting. To establish appropriate incubation conditions, we conducted a series of uptake studies, before genotoxicity was determined by DNA strand break induction in HeLa cells and mutagenicity in V79 Chinese hamster cells. Co(II) is taken up by HeLa cells in a concentration‐dependent manner and is accumulated inside the cell. The uptake is preceded by a fast association step to the outer membrane, with no saturation up to 24 h. DNA strand breaks as determined by nucleoid sedimentation are induced at concentrations as low as 50μMCoCl₂. The induction is time‐dependent, showing the highest number of breaks after 4h incubation with no further increase up to 24h. CoCl₂ is mutagenic at the HPRT‐locus, enhancing the spontaneous mutation frequency 4.2‐fold at 100μ?. Besides direct interactions with DNA, the mutagenicity of CoCl₂ could also be due to a decrease in the Fidelity of DNA polymerisation.     

Recycling glass-polishing sludge and aluminum anodising sludge in polyurethane and cement composites: fire performance and mechanical properties

Journal of Material Cycles and Waste Management - This article aims to study the mechanical strength and fire resistance of polyurethane/cement (PuCem) composites containing glass sludge and sludge...     

C and N Content in Density Fractions of Whole Soil and Soil Size Fraction Under Cacao Agroforestry Systems and Natural Forest in Bahia,Brazil

Agroforestry systems (AFSs) have an important role in capturing above and below ground soil carbon and play a dominant role in mitigation of atmospheric CO₂. Attempts has been made here to identify soil organic matter fractions in the cacao-AFSs that have different susceptibility to microbial decomposition and further represent the basis of understanding soil C dynamics. The objective of this study was to characterize the organic matter density fractions and soil size fractions in soils of two types of cacao agroforestry systems and to compare with an adjacent natural forest in Bahia, Brazil. The land-use systems studied were: (1) a 30-year-old stand of natural forest with cacao (cacao cabruca), (2) a 30-year-old stand of cacao with Erythrina glauca as shade trees (cacao + erythrina), and (3) an adjacent natural forest without cacao. Soil samples were collected from 0-10 cm depth layer in reddish-yellow Oxisols. Soil samples was separated by wet sieving into five fraction-size classes (>2000 μm, 1000–2000 μm, 250–1000 μm, 53–250 μm, and <53 μm). C and N accumulated in to the light (free- and intra-aggregate density fractions) and heavy fractions of whole soil and soil size fraction were determined. Soil size fraction obtained in cacao AFS soils consisted mainly (65 %) of mega-aggregates (>2000 μm) mixed with macroaggregates (32–34%), and microaggregates (1–1.3%). Soil organic carbon (SOC) and total N content increased with increasing soil size fraction in all land-use systems. Organic C-to-total N ratio was higher in the macroaggregate than in the microaggregate. In general, in natural forest and cacao cabruca the contribution of C and N in the light and heavy fractions was similar. However, in cacao + erythrina the heavy fraction was the most common and contributed 67% of C and 63% of N. Finding of this study shows that the majority of C and N in all three systems studied are found in macroaggregates, particularly in the 250–1000 μm size aggregate class. The heavy fraction was the most common organic matter fraction in these soils. Thus, in mature cacao AFS on highly weathered soils the main mechanisms of C stabilization could be the physical protection within macroaggregate structures thereby minimizing the impact of conversion of forest to cacao AFS.     

Arsenic,antimony, and other trace element contamination in a mine tailings affected area and uptake by tolerant plant species

The study was conducted to characterize mineralogical and elemental composition of mine tailings in order to evaluate the environmental hazards, and identify the metal accumulation potential of native plant species from São Domingos mine, one of the long-term activity mines of the Iberian Pyrite Belt dating back to pre-Roman times. The mine tailings including soils and different plant species from São Domingos were analyzed for determination of tailings characteristics and chemical element contents in tailings and plants. The large amounts of mining wastes are causing significant adverse environment impacts due to acid mine drainage production and mobilization of potentially toxic metals and metalloids in residential areas, agricultural fields, downstreams, and rivers. The typical mineralogical composition is as follows: quartz, micas, K-feldspar, olivine-group minerals, magnetite, goethite, hematite, jarosite, and sulfides. The mine tailings were highly contaminated by As, Ag, Cr, Hg, Sn, Sb, Fe, and Zn; and among them, As and Sb, main contaminants, attained the highest concentrations except Fe. Arsenic has exhibited very good correlations with Au, Fe, Sb, Se, and W; and Sb with As, Au, Fe, Se, Sn, and W in tailings. Among the all plant species, the higher concentrations of all the metals were noted in Erica andevalensis, Erica australis, Echium plantagium, and Lavandula luisierra. Considering the tolerant behavior and abundant growth, the plant species Erica australis, Erica andevalensis, Lavandula luisierra, Daphne gnidium, Rumex induratus, Ulex eriocladus, Juncus, and Genista hirsutus are of major importance for the rehabilitation and recovery of degraded São Domingos mining area.     

Regional-scale meteorological characteristics of the Vento Norte phenomenon observed in Southern Brazil

Environmental Fluid Mechanics - The sudden increase in air temperature associated with strong gusty winds of northerly direction is a phenomenon occasionally observed during the cold season in the...     

Life cycle inventory of recycled aggregates derived from construction and demolition waste

Journal of Material Cycles and Waste Management - This study is performed to identify environmental aspects that can be improved during the derivation of recycled aggregates (RAs) from construction...     

1,4-Dioxane removal from water and membrane fouling elimination using CuO-coated ceramic membrane coupled with ozone

Environmental Science and Pollution Research - 1,4-Dioxane is a synthetic cyclic ether traditionally used as a chlorinated solvent stabilizer. It is a small molecule and recalcitrant compound that...     

Carbon Storage in Soil Size Fractions Under Two Cacao Agroforestry Systems in Bahia, Brazil

Shaded perennial agroforestry systems contain relatively high quantities of soil carbon (C) resulting from continuous deposition of plant residues; however, the extent to which the C is sequestered in soil will depend on the extent of physical protection of soil organic C (SOC). The main objective of this study was to characterize SOC storage in relation to soil fraction-size classes in cacao (Theobroma cacao L.) agroforestry systems (AFSs). Two shaded cacao systems and an adjacent natural forest in reddish-yellow Oxisols in Bahia, Brazil were selected. Soil samples were collected from four depth classes to 1 m depth and separated by wet-sieving into three fraction-size classes (>250 μm, 250–53 μm, and <53 μm)—corresponding to macroaggregate, microaggregate, and silt-and-clay size fractions—and analyzed for C content. The total SOC stock did not vary among systems (mean: 302 Mg/ha). On average, 72% of SOC was in macroaggregate-size, 20% in microaggregate-size, and 8% in silt-and-clay size fractions in soil. Sonication of aggregates showed that occlusion of C in soil aggregates could be a major mechanism of C protection in these soils. Considering the low level of soil disturbances in cacao AFSs, the C contained in the macroaggregate fraction might become stabilized in the soil. The study shows the role of cacao AFSs in mitigating greenhouse gas (GHG) emission through accumulation and retention of high amounts of organic C in the soils and suggests the potential benefit of this environmental service to the nearly 6 million cacao farmers worldwide.