TY - JOUR
T1 - Mobilization of arsenic from coal fly ash in the presence of dissolved organic matter
AU - Deonarine, Amrika
AU - Kolker, Allan
AU - Doughten, Michael W.
AU - Holland, James T.
AU - Bailoo, Jeremy D.
N1 - Funding Information:
The authors thank Harvey Belkin, John Jackson, Frank Dulong and the Microbiology Lab at the U.S. Geological Survey Reston VA, Frank Huggins (University of Kentucky), Grace Schwartz (Duke University), and Andrea Foster (U.S. Geological Survey Menlo Park CA) for assistance with experimental setup, help with analyses, and providing model compounds for synchrotron work. We also thank Leslie Ruppert, Kevin Jones, and Brett Valentine (U.S. Geological Survey Reston VA) for assistance with sample collection. This study was funded by a U.S. Geological Survey Mendenhall Postdoctoral Fellowship awarded to Amrika Deonarine. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , is supported by the United States Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515 . The TEM-SAED results presented were obtained in part with the instruments and staff expertise at Virginia Tech's Nanoscale Characterization and Fabrication Laboratory (NCFL).
Funding Information:
The authors thank Harvey Belkin, John Jackson, Frank Dulong and the Microbiology Lab at the U.S. Geological Survey Reston VA, Frank Huggins (University of Kentucky), Grace Schwartz (Duke University), and Andrea Foster (U.S. Geological Survey Menlo Park CA) for assistance with experimental setup, help with analyses, and providing model compounds for synchrotron work. We also thank Leslie Ruppert, Kevin Jones, and Brett Valentine (U.S. Geological Survey Reston VA) for assistance with sample collection. This study was funded by a U.S. Geological Survey Mendenhall Postdoctoral Fellowship awarded to Amrika Deonarine. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the United States Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. The TEM-SAED results presented were obtained in part with the instruments and staff expertise at Virginia Tech's Nanoscale Characterization and Fabrication Laboratory (NCFL).
Publisher Copyright:
© 2021
PY - 2021/5
Y1 - 2021/5
N2 - In this study, we examined the influence of dissolved organic matter (humic and fulvic acids) on arsenic (As) mobilization from two Class F coal fly ashes under oxic and anoxic conditions. Batch leaching experiments were conducted to examine As leaching behavior and changes in As aqueous and solid phase speciation after exposure to humic and fulvic acids for up to 4 weeks (ash/buffer ratio = 0.01 g/mL). Under oxic conditions, mobilized As concentrations increased compared to the organic-free controls and were positively correlated with percent aliphatic carbon and oxygen/carbon ratio of the humic and fulvic acids, suggesting both non-specific hydrophobic association of the organic matter with the surface of the fly ash particles and competitive desorption between negatively charged organic functional groups and As anions adsorbed to mineral surfaces. Under anoxic conditions, organic matter enhanced the reductive dissolution of As-bearing iron oxides such as hematite, resulting in increased As mobilization. X-ray absorption spectroscopy indicated that the majority of As in the leached and unleached fly ash was As(V) (≥90%), with As(V)-ferrihydrite precipitation occurring under all leaching conditions tested. Our results demonstrated that humic and fulvic acids are capable of mobilizing As from fly ash under both oxic and anoxic conditions, though redox appeared to be a larger driver of As mobilization compared to dissolved organic matter (DOM). DOM is a parameter which should be considered in risk assessment strategies for fly ash that is exposed to water (e.g., subsurface infiltration) or released to aquatic systems.
AB - In this study, we examined the influence of dissolved organic matter (humic and fulvic acids) on arsenic (As) mobilization from two Class F coal fly ashes under oxic and anoxic conditions. Batch leaching experiments were conducted to examine As leaching behavior and changes in As aqueous and solid phase speciation after exposure to humic and fulvic acids for up to 4 weeks (ash/buffer ratio = 0.01 g/mL). Under oxic conditions, mobilized As concentrations increased compared to the organic-free controls and were positively correlated with percent aliphatic carbon and oxygen/carbon ratio of the humic and fulvic acids, suggesting both non-specific hydrophobic association of the organic matter with the surface of the fly ash particles and competitive desorption between negatively charged organic functional groups and As anions adsorbed to mineral surfaces. Under anoxic conditions, organic matter enhanced the reductive dissolution of As-bearing iron oxides such as hematite, resulting in increased As mobilization. X-ray absorption spectroscopy indicated that the majority of As in the leached and unleached fly ash was As(V) (≥90%), with As(V)-ferrihydrite precipitation occurring under all leaching conditions tested. Our results demonstrated that humic and fulvic acids are capable of mobilizing As from fly ash under both oxic and anoxic conditions, though redox appeared to be a larger driver of As mobilization compared to dissolved organic matter (DOM). DOM is a parameter which should be considered in risk assessment strategies for fly ash that is exposed to water (e.g., subsurface infiltration) or released to aquatic systems.
KW - Arsenic
KW - Coal fly ash
KW - DOM
KW - Organic matter
KW - Redox
UR - http://www.scopus.com/inward/record.url?scp=85104319873&partnerID=8YFLogxK
U2 - 10.1016/j.apgeochem.2021.104950
DO - 10.1016/j.apgeochem.2021.104950
M3 - Article
AN - SCOPUS:85104319873
VL - 128
JO - Applied Geochemistry
JF - Applied Geochemistry
SN - 0883-2927
M1 - 104950
ER -