The Experts below are selected from a list of 17172 Experts worldwide ranked by ideXlab platform

Roel Cruz - One of the best experts on this subject based on the ideXlab platform.

  • Arsenopyrite weathering under conditions of simulated Calcareous Soil
    Environmental Science and Pollution Research, 2016
    Co-Authors: Rene H Lara, Manuel Dossot, Leticia J. Velázquez, Jorge Vazquez-arenas, Martine Mallet, Israel Labastida, Fabiola S. Sosa-rodríguez, León F. Espinosa-cristóbal, Miguel A. Escobedo-bretado, Roel Cruz
    Abstract:

    Mining activities release arsenopyrite into Calcareous Soils where it undergoes weathering generating toxic compounds. The research evaluates the environmental impacts of these processes under semi-alkaline carbonated conditions. Electrochemical (cyclic voltammetry, chronoamperometry, EIS), spectroscopic (Raman, XPS), and microscopic (SEM, AFM, TEM) techniques are combined along with chemical analyses of leachates collected from simulated arsenopyrite weathering to comprehensively examine the interfacial mechanisms. Early oxidation stages enhance mineral reactivity through the formation of surface sulfur phases (e.g., S (n) (2-)/S-0) with semiconductor properties, leading to oscillatory mineral reactivity. Subsequent steps entail the generation of intermediate siderite (FeCO3)-like, followed by the formation of low-compact mass sub-micro ferric oxyhydroxides (alpha, gamma-FeOOH) with adsorbed arsenic (mainly As(III), and lower amounts of As(V)). In addition, weathering reactions can be influenced by accessible arsenic resulting in the formation of a symplesite (Fe-3(AsO4)(3))-like compound which is dependent on the amount of accessible arsenic in the system. It is proposed that arsenic release occurs via diffusion across secondary alpha, gamma-FeOOH structures during arsenopyrite weathering. We suggest weathering mechanisms of arsenopyrite in Calcareous Soil and environmental implications based on experimental data.

  • An experimental study of iron sulfides weathering under simulated Calcareous Soil conditions
    Environmental Earth Sciences, 2015
    Co-Authors: Rene H Lara, Manuel Dossot, Martine Mallet, Marcos G. Monroy, Ma Azucena González, Roel Cruz
    Abstract:

    In Calcareous sites, hard rock mining activities release pyrite (FeS2), pyrrhotite (Fe1-x S) and other sulfides to Soils. The sulfides then undergo weathering processes, generating acid rock drainage and secondary compounds. Despite the potentially important environmental impacts, very few studies have considered the mechanisms of pyrite and pyrrhotite weathering and the transformation of secondary compounds under neutral-alkaline carbonated conditions. In this study, we used an experimental approach combining electrochemical, microscopic and spectroscopic techniques to examine the interfacial processes involved in pyrite and pyrrhotite weathering under simulated Calcareous Soil conditions. The results showed an initial oxidation step with the formation of variable amounts of surface sulfur compounds (e.g., polysulfides, S (n) (2-) , and elementary sulfur, S-0) and acid generation, leading to significant modification of the oxidative behavior of the minerals. The surface changes that occurred as a result of mineral weathering provoked transient enhancement of pyrite reactivity and progressive passivation in the pyrrhotite system. Iron sulfides weathering was found to involve the formation of an intermediate siderite (FeCO3)-like compound, preceding the predominant formation of K-jarosite (K center dot Fe-3(SO4)(2)(OH)(6)) and/or ferric oxyhydroxide (alpha, gamma-FeOOH) compounds, depending on the surface acid condition reached in the systems. Mechanisms of pyrite and pyrrhotite weathering in Calcareous Soils are suggested on the basis of surface characterization and chemical analysis of the leachates generated, and the environmental implications are discussed.

  • galena weathering under simulated Calcareous Soil conditions
    Science of The Total Environment, 2011
    Co-Authors: Rene H Lara, Roberto Briones, Marcos Monroy, Martine Mullet, Bernard Humbert, Ghinwa Naja, Manuel Dossot, Roel Cruz
    Abstract:

    Exploitation of polymetallic deposits from Calcareous mining sites exposes galena and others sulfides to weathering factors. Galena weathering leads to the formation of lead phases (e.g., PbSO4, PbCO3) with a higher bioaccessibility than galena, thus increasing the mobility and toxicity of lead. Despite the environmental impacts of these lead phases, the mechanisms of galena oxidation and the transformation of lead secondary phases, under neutral-alkaline carbonated conditions, have rarely been studied. In this work, an experimental approach, combining electrochemical and spectroscopic techniques, was developed to examine the interfacial processes involved in the galena weathering under simulated Calcareous conditions. The results showed an initial oxidation stage with the formation of an anglesite-like phase leading to the partial mineral passivation. Under neutral-alkaline carbonated conditions, the stability of this phase was limited as it transformed into a cerussite-like one. Based on the surface characterization and the formation of secondary species, the weathering mechanisms of galena in Calcareous Soil and its environmental implications were suggested.

  • galena weathering under simulated Calcareous Soil conditions
    Science of The Total Environment, 2011
    Co-Authors: Rene H Lara, Roberto Briones, Marcos Monroy, Martine Mullet, Bernard Humbert, Ghinwa Naja, Manuel Dossot, Roel Cruz
    Abstract:

    Exploitation of polymetallic deposits from Calcareous mining sites exposes galena and others sulfides to weathering factors. Galena weathering leads to the formation of lead phases (e.g., PbSO4, PbCO3) with a higher bioaccessibility than galena, thus increasing the mobility and toxicity of lead. Despite the environmental impacts of these lead phases, the mechanisms of galena oxidation and the transformation of lead secondary phases, under neutral-alkaline carbonated conditions, have rarely been studied. In this work, an experimental approach, combining electrochemical and spectroscopic techniques, was developed to examine the interfacial processes involved in the galena weathering under simulated Calcareous conditions. The results showed an initial oxidation stage with the formation of an anglesite-like phase leading to the partial mineral passivation. Under neutral-alkaline carbonated conditions, the stability of this phase was limited as it transformed into a cerussite-like one. Based on the surface characterization and the formation of secondary species, the weathering mechanisms of galena in Calcareous Soil and its environmental implications were suggested.

Rene H Lara - One of the best experts on this subject based on the ideXlab platform.

  • Arsenopyrite weathering under conditions of simulated Calcareous Soil
    Environmental Science and Pollution Research, 2016
    Co-Authors: Rene H Lara, Manuel Dossot, Leticia J. Velázquez, Jorge Vazquez-arenas, Martine Mallet, Israel Labastida, Fabiola S. Sosa-rodríguez, León F. Espinosa-cristóbal, Miguel A. Escobedo-bretado, Roel Cruz
    Abstract:

    Mining activities release arsenopyrite into Calcareous Soils where it undergoes weathering generating toxic compounds. The research evaluates the environmental impacts of these processes under semi-alkaline carbonated conditions. Electrochemical (cyclic voltammetry, chronoamperometry, EIS), spectroscopic (Raman, XPS), and microscopic (SEM, AFM, TEM) techniques are combined along with chemical analyses of leachates collected from simulated arsenopyrite weathering to comprehensively examine the interfacial mechanisms. Early oxidation stages enhance mineral reactivity through the formation of surface sulfur phases (e.g., S (n) (2-)/S-0) with semiconductor properties, leading to oscillatory mineral reactivity. Subsequent steps entail the generation of intermediate siderite (FeCO3)-like, followed by the formation of low-compact mass sub-micro ferric oxyhydroxides (alpha, gamma-FeOOH) with adsorbed arsenic (mainly As(III), and lower amounts of As(V)). In addition, weathering reactions can be influenced by accessible arsenic resulting in the formation of a symplesite (Fe-3(AsO4)(3))-like compound which is dependent on the amount of accessible arsenic in the system. It is proposed that arsenic release occurs via diffusion across secondary alpha, gamma-FeOOH structures during arsenopyrite weathering. We suggest weathering mechanisms of arsenopyrite in Calcareous Soil and environmental implications based on experimental data.

  • An experimental study of iron sulfides weathering under simulated Calcareous Soil conditions
    Environmental Earth Sciences, 2015
    Co-Authors: Rene H Lara, Manuel Dossot, Martine Mallet, Marcos G. Monroy, Ma Azucena González, Roel Cruz
    Abstract:

    In Calcareous sites, hard rock mining activities release pyrite (FeS2), pyrrhotite (Fe1-x S) and other sulfides to Soils. The sulfides then undergo weathering processes, generating acid rock drainage and secondary compounds. Despite the potentially important environmental impacts, very few studies have considered the mechanisms of pyrite and pyrrhotite weathering and the transformation of secondary compounds under neutral-alkaline carbonated conditions. In this study, we used an experimental approach combining electrochemical, microscopic and spectroscopic techniques to examine the interfacial processes involved in pyrite and pyrrhotite weathering under simulated Calcareous Soil conditions. The results showed an initial oxidation step with the formation of variable amounts of surface sulfur compounds (e.g., polysulfides, S (n) (2-) , and elementary sulfur, S-0) and acid generation, leading to significant modification of the oxidative behavior of the minerals. The surface changes that occurred as a result of mineral weathering provoked transient enhancement of pyrite reactivity and progressive passivation in the pyrrhotite system. Iron sulfides weathering was found to involve the formation of an intermediate siderite (FeCO3)-like compound, preceding the predominant formation of K-jarosite (K center dot Fe-3(SO4)(2)(OH)(6)) and/or ferric oxyhydroxide (alpha, gamma-FeOOH) compounds, depending on the surface acid condition reached in the systems. Mechanisms of pyrite and pyrrhotite weathering in Calcareous Soils are suggested on the basis of surface characterization and chemical analysis of the leachates generated, and the environmental implications are discussed.

  • galena weathering under simulated Calcareous Soil conditions
    Science of The Total Environment, 2011
    Co-Authors: Rene H Lara, Roberto Briones, Marcos Monroy, Martine Mullet, Bernard Humbert, Ghinwa Naja, Manuel Dossot, Roel Cruz
    Abstract:

    Exploitation of polymetallic deposits from Calcareous mining sites exposes galena and others sulfides to weathering factors. Galena weathering leads to the formation of lead phases (e.g., PbSO4, PbCO3) with a higher bioaccessibility than galena, thus increasing the mobility and toxicity of lead. Despite the environmental impacts of these lead phases, the mechanisms of galena oxidation and the transformation of lead secondary phases, under neutral-alkaline carbonated conditions, have rarely been studied. In this work, an experimental approach, combining electrochemical and spectroscopic techniques, was developed to examine the interfacial processes involved in the galena weathering under simulated Calcareous conditions. The results showed an initial oxidation stage with the formation of an anglesite-like phase leading to the partial mineral passivation. Under neutral-alkaline carbonated conditions, the stability of this phase was limited as it transformed into a cerussite-like one. Based on the surface characterization and the formation of secondary species, the weathering mechanisms of galena in Calcareous Soil and its environmental implications were suggested.

  • galena weathering under simulated Calcareous Soil conditions
    Science of The Total Environment, 2011
    Co-Authors: Rene H Lara, Roberto Briones, Marcos Monroy, Martine Mullet, Bernard Humbert, Ghinwa Naja, Manuel Dossot, Roel Cruz
    Abstract:

    Exploitation of polymetallic deposits from Calcareous mining sites exposes galena and others sulfides to weathering factors. Galena weathering leads to the formation of lead phases (e.g., PbSO4, PbCO3) with a higher bioaccessibility than galena, thus increasing the mobility and toxicity of lead. Despite the environmental impacts of these lead phases, the mechanisms of galena oxidation and the transformation of lead secondary phases, under neutral-alkaline carbonated conditions, have rarely been studied. In this work, an experimental approach, combining electrochemical and spectroscopic techniques, was developed to examine the interfacial processes involved in the galena weathering under simulated Calcareous conditions. The results showed an initial oxidation stage with the formation of an anglesite-like phase leading to the partial mineral passivation. Under neutral-alkaline carbonated conditions, the stability of this phase was limited as it transformed into a cerussite-like one. Based on the surface characterization and the formation of secondary species, the weathering mechanisms of galena in Calcareous Soil and its environmental implications were suggested.

Manuel Dossot - One of the best experts on this subject based on the ideXlab platform.

  • Arsenopyrite weathering under conditions of simulated Calcareous Soil
    Environmental Science and Pollution Research, 2016
    Co-Authors: Rene H Lara, Manuel Dossot, Leticia J. Velázquez, Jorge Vazquez-arenas, Martine Mallet, Israel Labastida, Fabiola S. Sosa-rodríguez, León F. Espinosa-cristóbal, Miguel A. Escobedo-bretado, Roel Cruz
    Abstract:

    Mining activities release arsenopyrite into Calcareous Soils where it undergoes weathering generating toxic compounds. The research evaluates the environmental impacts of these processes under semi-alkaline carbonated conditions. Electrochemical (cyclic voltammetry, chronoamperometry, EIS), spectroscopic (Raman, XPS), and microscopic (SEM, AFM, TEM) techniques are combined along with chemical analyses of leachates collected from simulated arsenopyrite weathering to comprehensively examine the interfacial mechanisms. Early oxidation stages enhance mineral reactivity through the formation of surface sulfur phases (e.g., S (n) (2-)/S-0) with semiconductor properties, leading to oscillatory mineral reactivity. Subsequent steps entail the generation of intermediate siderite (FeCO3)-like, followed by the formation of low-compact mass sub-micro ferric oxyhydroxides (alpha, gamma-FeOOH) with adsorbed arsenic (mainly As(III), and lower amounts of As(V)). In addition, weathering reactions can be influenced by accessible arsenic resulting in the formation of a symplesite (Fe-3(AsO4)(3))-like compound which is dependent on the amount of accessible arsenic in the system. It is proposed that arsenic release occurs via diffusion across secondary alpha, gamma-FeOOH structures during arsenopyrite weathering. We suggest weathering mechanisms of arsenopyrite in Calcareous Soil and environmental implications based on experimental data.

  • An experimental study of iron sulfides weathering under simulated Calcareous Soil conditions
    Environmental Earth Sciences, 2015
    Co-Authors: Rene H Lara, Manuel Dossot, Martine Mallet, Marcos G. Monroy, Ma Azucena González, Roel Cruz
    Abstract:

    In Calcareous sites, hard rock mining activities release pyrite (FeS2), pyrrhotite (Fe1-x S) and other sulfides to Soils. The sulfides then undergo weathering processes, generating acid rock drainage and secondary compounds. Despite the potentially important environmental impacts, very few studies have considered the mechanisms of pyrite and pyrrhotite weathering and the transformation of secondary compounds under neutral-alkaline carbonated conditions. In this study, we used an experimental approach combining electrochemical, microscopic and spectroscopic techniques to examine the interfacial processes involved in pyrite and pyrrhotite weathering under simulated Calcareous Soil conditions. The results showed an initial oxidation step with the formation of variable amounts of surface sulfur compounds (e.g., polysulfides, S (n) (2-) , and elementary sulfur, S-0) and acid generation, leading to significant modification of the oxidative behavior of the minerals. The surface changes that occurred as a result of mineral weathering provoked transient enhancement of pyrite reactivity and progressive passivation in the pyrrhotite system. Iron sulfides weathering was found to involve the formation of an intermediate siderite (FeCO3)-like compound, preceding the predominant formation of K-jarosite (K center dot Fe-3(SO4)(2)(OH)(6)) and/or ferric oxyhydroxide (alpha, gamma-FeOOH) compounds, depending on the surface acid condition reached in the systems. Mechanisms of pyrite and pyrrhotite weathering in Calcareous Soils are suggested on the basis of surface characterization and chemical analysis of the leachates generated, and the environmental implications are discussed.

  • galena weathering under simulated Calcareous Soil conditions
    Science of The Total Environment, 2011
    Co-Authors: Rene H Lara, Roberto Briones, Marcos Monroy, Martine Mullet, Bernard Humbert, Ghinwa Naja, Manuel Dossot, Roel Cruz
    Abstract:

    Exploitation of polymetallic deposits from Calcareous mining sites exposes galena and others sulfides to weathering factors. Galena weathering leads to the formation of lead phases (e.g., PbSO4, PbCO3) with a higher bioaccessibility than galena, thus increasing the mobility and toxicity of lead. Despite the environmental impacts of these lead phases, the mechanisms of galena oxidation and the transformation of lead secondary phases, under neutral-alkaline carbonated conditions, have rarely been studied. In this work, an experimental approach, combining electrochemical and spectroscopic techniques, was developed to examine the interfacial processes involved in the galena weathering under simulated Calcareous conditions. The results showed an initial oxidation stage with the formation of an anglesite-like phase leading to the partial mineral passivation. Under neutral-alkaline carbonated conditions, the stability of this phase was limited as it transformed into a cerussite-like one. Based on the surface characterization and the formation of secondary species, the weathering mechanisms of galena in Calcareous Soil and its environmental implications were suggested.

  • galena weathering under simulated Calcareous Soil conditions
    Science of The Total Environment, 2011
    Co-Authors: Rene H Lara, Roberto Briones, Marcos Monroy, Martine Mullet, Bernard Humbert, Ghinwa Naja, Manuel Dossot, Roel Cruz
    Abstract:

    Exploitation of polymetallic deposits from Calcareous mining sites exposes galena and others sulfides to weathering factors. Galena weathering leads to the formation of lead phases (e.g., PbSO4, PbCO3) with a higher bioaccessibility than galena, thus increasing the mobility and toxicity of lead. Despite the environmental impacts of these lead phases, the mechanisms of galena oxidation and the transformation of lead secondary phases, under neutral-alkaline carbonated conditions, have rarely been studied. In this work, an experimental approach, combining electrochemical and spectroscopic techniques, was developed to examine the interfacial processes involved in the galena weathering under simulated Calcareous conditions. The results showed an initial oxidation stage with the formation of an anglesite-like phase leading to the partial mineral passivation. Under neutral-alkaline carbonated conditions, the stability of this phase was limited as it transformed into a cerussite-like one. Based on the surface characterization and the formation of secondary species, the weathering mechanisms of galena in Calcareous Soil and its environmental implications were suggested.

Naoko K Nishizawa - One of the best experts on this subject based on the ideXlab platform.

  • A new transgenic rice line exhibiting enhanced ferric iron reduction and phytosiderophore production confers tolerance to low iron availability in Calcareous Soil.
    PloS one, 2017
    Co-Authors: Hiroshi Masuda, Yuko Ogo, Takanori Kobayashi, May Sann Aung, Hiromi Nakanishi, Erika Shimochi, Tatsuro Hamada, Takeshi Senoura, Yasuhiro Ishimaru, Naoko K Nishizawa
    Abstract:

    Iron (Fe) deficiency is a critical agricultural problem, especially in Calcareous Soil, which is distributed worldwide. Rice plants take up Fe(II) from Soil through a OsIRT1 transporter (Strategy I-related system) and also take up Fe(III) via a phytosiderophore-based system (Strategy II system). However, rice plants are susceptible to low-Fe conditions because they have low Fe(III) reduction activity and low-level phytosiderophore secretion. Previously, we produced transgenic rice plants expressing a mutationally reconstructed yeast ferric chelate reductase, refre1/372, under the control of the OsIRT1 promoter. This transgenic rice line exhibited higher Fe(III) chelate reductase activity and tolerance to Fe deficiency. In addition, we produced transgenic rice overexpressing the Fe deficiency-inducible transcription factor, OsIRO2, which regulates the expression of various genes involved in the strategy II Fe(III) uptake system, including OsNAS1, OsNAAT1, OsDMAS1, OsYSL15, and TOM1. This transgenic rice exhibited improved phytosiderophore secretion ability and tolerance to Fe deficiency. In the present research, transgenic rice plants that possess both the OsIRT1 promoter-refre1/372 and the 35S promoter-OsIRO2 (RI lines) were produced to enhance both Strategy I Fe(II) reductase ability and Strategy II phytosiderophore productivity. RI lines exhibited enhanced tolerance to Fe-deficient conditions at the early and middle-late stages of growth in Calcareous Soil, compared to both the non-transgenic line and lines harboring either OsIRT1 promoter-refre1/372 or 35S promoter-OsIRO2 alone. RI lines also exhibited a 9-fold higher yield than the non-transgenic line. Moreover, we successfully produced Fe-deficiency-tolerant Tachisugata rice, which is a high-biomass variety used as fodder. Collectively, our results demonstrate that combined enhancement of two Fe uptake systems in rice is highly effective in conferring tolerance to low Fe availability in Calcareous Soil.

  • osiro2 is responsible for iron utilization in rice and improves growth and yield in Calcareous Soil
    Plant Molecular Biology, 2011
    Co-Authors: Yuko Ogo, Reiko Nakanishi Itai, Takanori Kobayashi, May Sann Aung, Hiromi Nakanishi, Naoko K Nishizawa
    Abstract:

    Iron (Fe) deficiency, a worldwide agricultural problem on Calcareous Soil with low Fe availability, is also a major human nutritional deficit. Plants induce Fe acquisition systems under conditions of low Fe availability. Previously, we reported that an Fe-deficiency-inducible basic helix-loop-helix (bHLH) transcription factor, OsIRO2, is responsible for regulation of the genes involved in Fe homeostasis in rice. Using promoter-GUS transformants, we showed that OsIRO2 is expressed throughout a plant’s lifetime in a spatially and temporally similar manner to the genes OsNAS1, OsNAS2 and TOM1, which is involved in Fe absorption and translocation. During germination, OsIRO2 expression was detected in embryos. OsIRO2 expression in vegetative tissues was restricted almost exclusively to vascular bundles of roots and leaves, and to the root exodermis under Fe-sufficient conditions, and expanded to all tissues of roots and leaves in response to Fe deficiency. OsIRO2 expression was also detected in flowers and developing seeds. Plants overexpressing OsIRO2 grew better, and OsIRO2-repressed plants showed poor growth compared to non-transformant rice after germination. OsIRO2 overexpression also resulted in improved tolerance to low Fe availability in Calcareous Soil. In addition to increased Fe content in shoots, the overexpression plants accumulated higher amounts of Fe in seeds than non-transformants when grown on Calcareous Soil. These results suggest that OsIRO2 is synchronously expressed with genes involved in Fe homeostasis, and performs a crucial function in regulation not only of Fe uptake from Soil but also Fe transport during germination and Fe translocation to grain during seed maturation.

Marcos Monroy - One of the best experts on this subject based on the ideXlab platform.

  • galena weathering under simulated Calcareous Soil conditions
    Science of The Total Environment, 2011
    Co-Authors: Rene H Lara, Roberto Briones, Marcos Monroy, Martine Mullet, Bernard Humbert, Ghinwa Naja, Manuel Dossot, Roel Cruz
    Abstract:

    Exploitation of polymetallic deposits from Calcareous mining sites exposes galena and others sulfides to weathering factors. Galena weathering leads to the formation of lead phases (e.g., PbSO4, PbCO3) with a higher bioaccessibility than galena, thus increasing the mobility and toxicity of lead. Despite the environmental impacts of these lead phases, the mechanisms of galena oxidation and the transformation of lead secondary phases, under neutral-alkaline carbonated conditions, have rarely been studied. In this work, an experimental approach, combining electrochemical and spectroscopic techniques, was developed to examine the interfacial processes involved in the galena weathering under simulated Calcareous conditions. The results showed an initial oxidation stage with the formation of an anglesite-like phase leading to the partial mineral passivation. Under neutral-alkaline carbonated conditions, the stability of this phase was limited as it transformed into a cerussite-like one. Based on the surface characterization and the formation of secondary species, the weathering mechanisms of galena in Calcareous Soil and its environmental implications were suggested.

  • galena weathering under simulated Calcareous Soil conditions
    Science of The Total Environment, 2011
    Co-Authors: Rene H Lara, Roberto Briones, Marcos Monroy, Martine Mullet, Bernard Humbert, Ghinwa Naja, Manuel Dossot, Roel Cruz
    Abstract:

    Exploitation of polymetallic deposits from Calcareous mining sites exposes galena and others sulfides to weathering factors. Galena weathering leads to the formation of lead phases (e.g., PbSO4, PbCO3) with a higher bioaccessibility than galena, thus increasing the mobility and toxicity of lead. Despite the environmental impacts of these lead phases, the mechanisms of galena oxidation and the transformation of lead secondary phases, under neutral-alkaline carbonated conditions, have rarely been studied. In this work, an experimental approach, combining electrochemical and spectroscopic techniques, was developed to examine the interfacial processes involved in the galena weathering under simulated Calcareous conditions. The results showed an initial oxidation stage with the formation of an anglesite-like phase leading to the partial mineral passivation. Under neutral-alkaline carbonated conditions, the stability of this phase was limited as it transformed into a cerussite-like one. Based on the surface characterization and the formation of secondary species, the weathering mechanisms of galena in Calcareous Soil and its environmental implications were suggested.