RESUMEN
The fates of cadmium (Cd) and arsenic (As) in paddy fields are generally opposite; thus, the inconsistent transformation of Cd and As poses large challenges for their remediation. In this study, the impacts of zero valent iron (ZVI) and/or biochar amendments on Cd and As bioavailability were examined in pot trials with rice. Comparison with the untreated soil, both Cd and As accumulation in different rice tissues decreased significantly in the ZVI-biochar amendments and the Cd and As accumulation in rice decreased with increasing ZVI contents. In particular, the concentrations of Cd (0.15 ± 0.01 mg kg-1) and As (0.17 ± 0.01 mg kg-1) in rice grains were decreased by 93% and 61% relative to the untreated soil, respectively. A sequential extraction analysis indicated that with increasing Fe ratios in the ZVI-biochar mixtures, bioavailable Cd and As decreased, and the immobilized Cd and As increased. Furthermore, high levels of Fe, Cd, and As were detected in Fe plaque of the ZVI-biochar amendments in comparison with the single biochar or single ZVI amendments. The ZVI-biochar mixture may have a synergistic effect that simultaneously reduces Cd and As bioavailability by increasing the formation of amorphous Fe and Fe plaque for Cd and As immobilization. The single ZVI amendment significantly decreased As bioavailability, while the single biochar amendment significantly reduced the bioavailability of Cd compared with the combined amendments. Hence, using a ZVI-biochar mixture as a soil amendment could be a promising strategy for safely-utilizing Cd and As co-contaminated sites in the future.
Asunto(s)
Arsénico/análisis , Cadmio/análisis , Carbón Orgánico/farmacología , Oryza/metabolismo , Arsénico/metabolismo , Disponibilidad Biológica , Cadmio/metabolismo , Contaminación Ambiental/análisis , Hierro/análisis , Suelo , Contaminantes del Suelo/análisisRESUMEN
The iron-catalyzed oxidation of arsenite (As(III)) associated with Fenton or Fenton-like reactions is one of the most efficient arsenic removal methods. However, the conventional chemical or electro-Fenton systems for the oxidation of As(III) are only efficient under acid conditions. In the present study, a cost-effective and efficient bio-electro-Fenton process was performed for As(III) oxidation in a dual-chamber microbial fuel cell (MFC) under neutral pH conditions. In such a system, the Fenton reagents, including H2O2 and Fe(II), were generated in situ by microbial-driven electro-reduction of O2 and γ-FeOOH, respectively, without an electricity supply. The results indicated that the process was capable of inducing As(III) oxidation with an apparent As(III) depletion first-order rate constant of 0.208 h(-1). The apparent oxidation current efficiency was calculated to be as high as 73.1%. The γ-FeOOH dosage in the cathode was an important factor in determining the system performance. Fourier-transform infrared spectroscopy (FT-IR) analysis indicated that As(V) was bound to the solid surface as a surface complex but not as a precipitated solid phase. The mechanism of bio-E-Fenton reaction for As(III) oxidation was also proposed. The bio-electro-Fenton system makes it potentially attractive method for the detoxification of As(III) from aqueous solution.
Asunto(s)
Arsenitos/química , Fuentes de Energía Bioeléctrica , Compuestos Férricos/química , Shewanella putrefaciens/metabolismo , Contaminantes Químicos del Agua/química , Compuestos Férricos/metabolismo , Peróxido de Hidrógeno/química , Concentración de Iones de Hidrógeno , Hierro/química , Oxidación-Reducción , Purificación del Agua/métodosRESUMEN
Sinus histiocytosis with massive lymphadenopathy (SHML), also known as Rosai-Dorfman disease (RDD), is an idiopathic histiocytic disorder of lymph nodes and extranodal sites. Central nervous system (CNS) manifestations, particularly in the absence of nodal disease, are rare. Intracranial RDD clinically and radiologically resembles meningioma, and histologic examination is essential for a definitive diagnosis. We report four patients with RDD primary to the CNS without evidence of other sites of involvement, review the literature, and discuss the clinical manifestations, pathology, treatment and outcome.