title: Enhanced Cr(VI) reduction and As(III) oxidation in ice phase: important role of dissolved organic matter from biochar.
abstract: This study evaluated the impact of DOM from two biochars (sugar beet tailing and Brazilian pepper) on Cr(VI) reduction and As(III) oxidation in both ice and aqueous phases with a soil DOM as control. Increasing DOM concentration from 3 to 300mgCL(-1) enhanced Cr(VI) reduction from 20% to 100% and As(III) oxidation from 6.2% to 25%; however, Cr(VI) reduction decreased from 80-86% to negligible while As(III) oxidation increased from negligible to 18-19% with increasing pH from 2 to 10. Electron spin resonance study suggested semiquinone radicals in DOM were involved in As(III) oxidation while Fourier transform infrared analysis suggested that carboxylic groups in DOM participated in both Cr(VI) reduction and As(III) oxidation. During Cr(VI) reduction, part of DOM (∼10%) was oxidized to CO2. The enhanced conversion of Cr(VI) and As(III) in the ice phase was due to the freeze concentration effect with elevated concentrations of electron donors and electron acceptors in the grain boundary. Though DOM enhanced both Cr(VI) reduction and As(III)oxidation, Cr(VI) reduction coupled with As(III) oxidation occurred in absence of DOM. The role of DOM, Cr(VI) and/or As(III) in Cr and As transformation may provide new insights into their speciation and toxicity in cold regions.
authors.affiliation: Department of Soil and Water Science, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Jiangsu 210046, China; Department of Soil and Water Science, University of Florida, Gainesville, FL 32611, USA. Electronic address: lqma@ufl.edu.
authors.forename: Lena Q
authors.initials: LQ
authors.lastname: Ma
authors.affiliation: Department of Soil and Water Science, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Gress
authors.affiliation: Department of Soil and Water Science, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Willie
authors.initials: W
authors.lastname: Harris
authors.affiliation: Soil and Water Science Department, Tropical Research and Education Center, University of Florida, Homestead, FL 33031-3314, USA.
authors.forename: Yuncong
authors.initials: Y
authors.lastname: Li
mesh_terms: D027926:Anacardiaceae / Q000737:chemistry; D001151:Arsenic / Q000737:chemistry*; D027461:Beta vulgaris / Q000737:chemistry; D002606:Charcoal / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D002857:Chromium / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: C540010:biochar; D002857:Chromium; D002606:Charcoal; D001151:Arsenic
keywords: As(III) oxidation; Biochar; Cr(VI) reduction; Dissolved organic matter