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Title: Impact of dissolved organic matter on mercury and methylmercury sorption to activated carbon in soils: implications for remediation

Abstract

Activated carbon (AC) amendments have shown promise in reducing inorganic mercury (Hg(II) complexes, “Hg”) and methylmercury (MeHg) risk in contaminated soils. However, the effectiveness of AC in Hg and MeHg immobilization has varied among studies, suggesting that site biogeochemistry might dictate efficacy. In this study, we examined the effect of dissolved organic matter (DOM) on MeHg and Hg sorption to AC. We evaluated the impact of Suwannee River Humic Acid (SRHA) on sorption to AC directly using an isotherm approach and in a soil/AC mixture using slurry microcosms. Aqueous sorption coefficients to AC (log K AC) for Hg-SRHA and MeHg-SRHA complexes were one to two orders of magnitude lower (Hg-SRHA = 4.53, MeHgSRHA = 4.35) than those for chloride complexes (HgCl 2 = 6.55, MeHgCl = 4.90) and more closely resembled the log K AC of SRHA (3.64). In anoxic, sulfidic soil slurries, the K AC for sulfide species appeared stronger than for chloride or SRHA species for both Hg and MeHg. AC significantly reduced porewater concentrations of both ambient MeHg and a fresh Me 199Hg spike, and the addition of up to 60 mg L -1 SRHA did not reduce sorption to AC. The AC also reduced ambient Hgmore » and 201Hg porewater concentrations, but as SRHA concentration increased, the magnitude of solid phase sorption decreased. Speciation modeling revealed that SRHA may have impacted Hg distribution to the solid phase by reducing HgS precipitation. In conclusion, this study highlights the need for site-specific evaluation of AC efficacy and the value in developing biogeochemical models of AC performance for Hg control.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1];  [3]; ORCiD logo [2]; ORCiD logo [1]
  1. Smithsonian Environmental Research Center, Edgewater, MD (United States)
  2. Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States). Dept. of Chemical, Biochemical, and Environmental Engineering
  3. The Dow Chemical Company, Midland, MI (United States). Environmental Remediation and Restoration
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE; National Institutes of Health (NIH)
OSTI Identifier:
1511919
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Environmental Science: Processes & Impacts
Additional Journal Information:
Journal Volume: 21; Journal Issue: 3; Journal ID: ISSN 2050-7887
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Schwartz, Grace E., Sanders, James P., McBurney, Alyssa M., Brown, Steven S., Ghosh, Upal, and Gilmour, Cynthia C. Impact of dissolved organic matter on mercury and methylmercury sorption to activated carbon in soils: implications for remediation. United States: N. p., 2019. Web. doi:10.1039/c8em00469b.
Schwartz, Grace E., Sanders, James P., McBurney, Alyssa M., Brown, Steven S., Ghosh, Upal, & Gilmour, Cynthia C. Impact of dissolved organic matter on mercury and methylmercury sorption to activated carbon in soils: implications for remediation. United States. doi:10.1039/c8em00469b.
Schwartz, Grace E., Sanders, James P., McBurney, Alyssa M., Brown, Steven S., Ghosh, Upal, and Gilmour, Cynthia C. Thu . "Impact of dissolved organic matter on mercury and methylmercury sorption to activated carbon in soils: implications for remediation". United States. doi:10.1039/c8em00469b.
@article{osti_1511919,
title = {Impact of dissolved organic matter on mercury and methylmercury sorption to activated carbon in soils: implications for remediation},
author = {Schwartz, Grace E. and Sanders, James P. and McBurney, Alyssa M. and Brown, Steven S. and Ghosh, Upal and Gilmour, Cynthia C.},
abstractNote = {Activated carbon (AC) amendments have shown promise in reducing inorganic mercury (Hg(II) complexes, “Hg”) and methylmercury (MeHg) risk in contaminated soils. However, the effectiveness of AC in Hg and MeHg immobilization has varied among studies, suggesting that site biogeochemistry might dictate efficacy. In this study, we examined the effect of dissolved organic matter (DOM) on MeHg and Hg sorption to AC. We evaluated the impact of Suwannee River Humic Acid (SRHA) on sorption to AC directly using an isotherm approach and in a soil/AC mixture using slurry microcosms. Aqueous sorption coefficients to AC (log KAC) for Hg-SRHA and MeHg-SRHA complexes were one to two orders of magnitude lower (Hg-SRHA = 4.53, MeHgSRHA = 4.35) than those for chloride complexes (HgCl2 = 6.55, MeHgCl = 4.90) and more closely resembled the log KAC of SRHA (3.64). In anoxic, sulfidic soil slurries, the KAC for sulfide species appeared stronger than for chloride or SRHA species for both Hg and MeHg. AC significantly reduced porewater concentrations of both ambient MeHg and a fresh Me199Hg spike, and the addition of up to 60 mg L-1 SRHA did not reduce sorption to AC. The AC also reduced ambient Hg and 201Hg porewater concentrations, but as SRHA concentration increased, the magnitude of solid phase sorption decreased. Speciation modeling revealed that SRHA may have impacted Hg distribution to the solid phase by reducing HgS precipitation. In conclusion, this study highlights the need for site-specific evaluation of AC efficacy and the value in developing biogeochemical models of AC performance for Hg control.},
doi = {10.1039/c8em00469b},
journal = {Environmental Science: Processes & Impacts},
number = 3,
volume = 21,
place = {United States},
year = {2019},
month = {1}
}

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Works referenced in this record:

Effect of chemical surface heterogeneity on the adsorption mechanism of dissolved aromatics on activated carbon
journal, January 2000