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RESEARCH ARTICLE
Contents Vol 7(1)

Roles of dissolved organic matter in the speciation of mercury and methylmercury in a contaminated ecosystem in Oak Ridge, Tennessee

Wenming Dong A , Liyuan Liang A , Scott Brooks A , George Southworth A and Baohua Gu A B
+ Author Affiliations
- Author Affiliations

A Oak Ridge National Laboratory, Environmental Sciences Division, PO Box 2008, MS 6036, Oak Ridge, TN 37831-6036, USA.

B Corresponding author. Email: gub1@ornl.gov

Environmental Chemistry 7(1) 94-102 https://doi.org/10.1071/EN09091
Submitted: 14 July 2009  Accepted: 13 January 2010   Published: 22 February 2010

Environmental context. Mercury (Hg) presents an environmental concern owing to its transformation to the potent neurotoxin methylmercury (CH3Hg+). The environmental factors that control bacterial methylation of mercury are poorly understood, but we know that methylmercury is bioaccumulated and biomagnified in aquatic food webs. We show that, even at low concentrations (~3 mg L–1), natural dissolved organic matter strongly complexes with ionic Hg2+ and CH3Hg+, thereby influencing biological uptake and methylation of Hg in aquatic environments.

Abstract. Complexation of the mercuric ion (Hg2+) and methylmercury (CH3Hg+) with organic and inorganic ligands influences mercury transformation and bioaccumulation in aquatic environments. Using aqueous geochemical modelling, we show that natural dissolved organic matter (DOM), even at low concentrations (~3 mg L–1), controls the Hg speciation by forming strong Hg-DOM and CH3Hg-DOM complexes through the reactive sulfur or thiol-like functional groups in DOM in the contaminated East Fork Poplar Creek at Oak Ridge, Tennessee. Concentrations of neutral Hg(OH)2, Hg(OH)Cl, CH3HgCl, and CH3HgOH species are negligible. Of the coexisting metal ions, only Zn2+, at concentrations of 1.6–2.6 × 10–7 M, competes with Hg2+ for binding with DOM, causing decrease in Hg-DOM complexation but having little impact on CH3Hg-DOM complexation. DOM may thus play a dominant role in controlling the transformation, biological uptake, and methylation of Hg in this contaminated ecosystem.

Additional keywords: aquatic environments, complexation, geochemical model, methylation, reduced sulfur, thiols.


Acknowledgements

This research is part of the Science Focus Area (SFA) at Oak Ridge National Laboratory (ORNL) supported by the Office of the Biological and Environmental Research, US Department of Energy (DOE). ORNL is managed by UT-Battelle LLC for US DOE under contract DE-AC05–00OR22725.


References


[1]   M. O. Barnett , L. A. Harris , R. R. Turner , R. J. Stevenson , T. J. Henson , R. C. Melton , D. P. Hoffman , Formation of mercuric sulfide in soil. Environ. Sci. Technol. 1997 , 31,  3037.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS |  open url image1

[2]   N. W. Revis , T. R. Osborne , G. Holdsworth , C. Hadden , Distribution of mercury species in soil from a mercury-contaminated site. Water Air Soil Pollut. 1989 , 45,  105.
        |  CAS | CAS |  open url image1

[3]   G. Southworth , M. J. Peterson , M. A. Bogle , Bioaccumulation factors for mercury in stream fish. Environ. Pract. 2004 , 6,  135.
        | Crossref | GoogleScholarGoogle Scholar |  open url image1

[4]   G. R. Southworth , M. J. Peterson , M. A. Bogle , Effect of point-source removal on mercury bioaccumulation in an industrial pond. Chemosphere 2002 , 49,  455.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[5]   G. R. Southworth , R. R. Turner , M. J. Peterson , M. A. Bogle , M. G. Ryon , Response of mercury contamination in fish to decreased aqueous concentrations and loading of inorganic mercury in a small stream. Environ. Monit. Assess. 2000 , 63,  481.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS |  open url image1

[6]   A. Amirbahman , A. L. Reid , T. A. Haines , J. S. Kahl , C. Arnold , Association of methylmercury with dissolved humic acids. Environ. Sci. Technol. 2002 , 36,  690.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed |  open url image1

[7]   Stumm W., Morgan J. J., Aquatic Chemistry 1995 (Wiley Interscience: New York).

[8]   K. Xia , U. L. Skyllberg , W. F. Bleam , P. R. Bloom , E. A. Nater , P. A. Helmke , X-ray absorption spectroscopic evidence for the complexation of Hg(II) by reduced sulfur in soil humic substances. Environ. Sci. Technol. 1999 , 33,  257.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS |  open url image1

[9]   M. Ravichandran , Interactions between mercury and dissolved organic matter – a review. Chemosphere 2004 , 55,  319.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[10]   U. Skyllberg , Competition among thiols and inorganic sulfides and polysulfides for Hg and MeHg in wetland soils and sediments under suboxic conditions: illumination of controversies and implications for MeHg net production. J. Geophys. Res. Biogeosci. 2008 , 113,  G00C03.
        | Crossref | GoogleScholarGoogle Scholar |  open url image1

[11]   M. Haitzer , G. R. Aiken , J. N. Ryan , Binding of mercury(II) to dissolved organic matter: the role of the mercury-to-DOM concentration ratio. Environ. Sci. Technol. 2002 , 36,  3564.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[12]   M. Haitzer , G. R. Aiken , J. N. Ryan , Binding of mercury(II) to aquatic humic substances: influence of pH and source of humic substances. Environ. Sci. Technol. 2003 , 37,  2436.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[13]   A. R. Khwaja , P. R. Bloom , P. L. Brezonik , Binding constants of divalent mercury (Hg2+) in soil humic acids and soil organic matter. Environ. Sci. Technol. 2006 , 40,  844.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[14]   S. H. Han , G. A. Gill , Determination of mercury complexation in coastal and estuarine waters using competitive ligand exchange method. Environ. Sci. Technol. 2005 , 39,  6607.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[15]   C. H. Lamborg , C. M. Tseng , W. F. Fitzgerald , P. H. Balcom , C. R. Hammerschmidt , Determination of the mercury complexation characteristics of dissolved organic matter in natural waters with ‘reducible Hg’ titrations. Environ. Sci. Technol. 2003 , 37,  3316.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[16]   D. Hesterberg , J. W. Chou , K. J. Hutchison , D. E. Sayers , Bonding of Hg(II) to reduced organic, sulfur in humic acid as affected by S/Hg ratio. Environ. Sci. Technol. 2001 , 35,  2741.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[17]   J. Qian , U. Skyllberg , W. Frech , W. F. Bleam , P. R. Bloom , P. E. Petit , Bonding of methyl mercury to reduced sulfur groups in soil and stream organic matter as determined by X-ray absorption spectroscopy and binding affinity studies. Geochim. Cosmochim. Acta 2002 , 66,  3873.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS |  open url image1

[18]   U. Skyllberg , P. R. Bloom , J. Qian , C. M. Lin , W. F. Bleam , Complexation of mercury(II) in soil organic matter: EXAFS evidence for linear two-coordination with reduced sulfur groups. Environ. Sci. Technol. 2006 , 40,  4174.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[19]   S. J. Yoon , L. M. Diener , P. R. Bloom , E. A. Nater , W. F. Bleam , X-ray absorption studies of CH3Hg+-binding sites in humic substances. Geochim. Cosmochim. Acta 2005 , 69,  1111.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS |  open url image1

[20]   Schnitzer M., Humic substances, chemistry and reactions, in Soil Organic Matter (Eds M. Schnitzer, S. U. E. Khan) 1978, pp. 1–64 (Elsevier: Amsterdam).

[21]   K. Xia , F. Weesner , W. F. Bleam , P. R. Bloom , U. L. Skyllberg , P. A. Helmke , XANES studies of oxidation states of sulfur in aquatic and soil humic substances. Soil Sci. Soc. Am. J. 1998 , 62,  1240.
        |  CAS | CAS |  open url image1

[22]   R. T. Drexel , M. Haitzer , J. N. Ryan , G. R. Aiken , K. L. Nagy , Mercury(II) sorption to two Florida Everglades peats: evidence for strong and weak binding and competition by dissolved organic matter released from the peat. Environ. Sci. Technol. 2002 , 36,  4058.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[23]   T. Barkay , M. Gillman , R. R. Turner , Effects of dissolved organic carbon and salinity on bioavailability of mercury. Appl. Environ. Microbiol. 1997 , 63,  4267.
        |  CAS | PubMed | PubMed |  open url image1

[24]   H. Hintelmann , K. Keppel-Jones , R. D. Evans , Constants of mercury methylation and demethylation rates in sediments and comparison of tracer and ambient mercury availability. Environ. Toxicol. Chem. 2000 , 19,  2204.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[25]   C. Miller , G. Southworth , S. C. Brooks , L. Liang , B. Gu , Kinetic controls on the complexation between mercury and dissolved organic matter in a contaminated environment. Environ. Sci. Technol. 2009 , 43,  8548.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[26]   Method 1631, Revised E: Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence Spectrometry, EPA-821-R-02–019 2002 (US EPA: Washington, DC).

[27]   Method 1630: Methyl Mercury in Water by Distillation, Aqueous Ethylation, Purge and Trap, and CVAFS, EPA-821-R-01–020 2001 (US EPA: Washington, DC).

[28]   P. Zhou , H. Yan , B. Gu , Competitive complexation of metal ions with humic substances. Chemosphere 2005 , 58,  1327.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[29]   J. F. McCarthy , B. Gu , L. Liang , J. Mas-Pla , T. M. Williams , T. C. J. Yeh , Field tracer tests on the mobility of natural organic matter in a sandy aquifer. Water Resour. Res. 1996 , 32,  1223.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[30]   Parkhurst D. L., Appelo C. A. J., User’s Guide to PHREEQC (Version 2) – A Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations 2004 (US Geological Survey: Denver, CO).

[31]   K. J. Powell , P. L. Brown , R. H. Byrne , T. Gajda , G. Hefter , S. Sjoberg , H. Wanner , Chemical speciation of environmentally significant heavy metals with inorganic ligands – Part 1: The Hg2+-Cl–, OH–, CO32–, SO42–, and PO43– aqueous systems – (IUPAC technical report). Pure Appl. Chem. 2005 , 77,  739.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[32]   Martell A. E.; Smith R. M.; Motekaitis R. J., NIST Critically Selected Stability Constants of Metal Complexes. NIST Standard Reference Database 46, 6.0 edn 2001 (National Institute of Standards and Technology: Gaithersburg, MD).

[33]   Langmuir D., Aqueous Environmental Chemistry 1997 (Prentice-Hall: New York).

[34]   J. Chen , B. Gu , E. J. LeBoeuf , H. Pan , S. Dai , Spectroscopic characterization of the structural and functional properties of natural organic matter fractions. Chemosphere 2002 , 48,  59.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[35]   I. Christl , R. Kretzschmar , Relating ion binding by fulvic and humic acids to chemical composition and molecular size. 1. Proton binding. Environ. Sci. Technol. 2001 , 35,  2505.
        | Crossref | GoogleScholarGoogle Scholar | CAS | CAS | PubMed | PubMed |  open url image1

[36]   Aiken G. R., McKnight D. M., Wershaw R. L., MacCarthy P., Humic Substances in Soil, Sediment, and Water 1985 (Wiley: New York).

[37]   J. M. Benoit , R. P. Mason , C. C. Gilmour , G. R. Aiken , Constants for mercury binding by dissolved organic matter isolates from the Florida Everglades. Geochim. Cosmochim. Acta 2001 , 65,  4445.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[38]   N. J. O’Driscoll , R. D. Evans , Analysis of methyl mercury binding to freshwater humic and fulvic acids by gel permeation chromatography/hydride generation ICP-MS. Environ. Sci. Technol. 2000 , 34,  4039.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[39]   T. Karlsson , U. Skyllberg , Bonding of ppb levels of methyl mercury to reduced sulfur groups in soil organic matter. Environ. Sci. Technol. 2003 , 37,  4912.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[40]   H. Hsu , D. L. Sedlak , Strong Hg(II) complexation in municipal wastewater effluent and surface waters. Environ. Sci. Technol. 2003 , 37,  2743.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[41]   F. J. Black , K. W. Bruland , A. R. Flegal , Competing ligand exchange–solid phase extraction method for the determination of the complexation of dissolved inorganic mercury(II) in natural waters. Anal. Chim. Acta 2007 , 598,  318.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[42]   U. Skyllberg , J. Qian , W. Frech , Combined XANES and EXAFS study on the bonding of methyl mercury to thiol group in soil and aquatic organic matter. Phys. Scr. 2005 , T115,  894.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[43]   H. Hintelmann , P. M. Welbourn , R. D. Evans , Binding of methylmercury compounds by humic and fulvic-acids. Water Air Soil Pollut. 1995 , 80,  1031.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[44]   H. Hintelmann , P. M. Welbourn , R. D. Evans , Measurement of complexation of methylmercury(II) compounds by freshwater humic substances using equilibrium dialysis. Environ. Sci. Technol. 1997 , 31,  489.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[45]   D. S. Smith , R. A. Bell , J. R. Kramer , Metal speciation in natural waters with emphasis on reduced sulfur groups as strong metal binding sites. Comp. Biochem. Phys. C 2002 , 133,  65.
         open url image1

[46]   T. Karlsson , U. Skyllberg , Complexation of zinc in organic soils – EXAFS evidence for sulfur associations. Environ. Sci. Technol. 2007 , 41,  119.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[47]   F. J. Stevenson , Stability-constants of Cu2+, Pb2+, and Cd2+ complexes with humic acids. Soil Sci. Soc. Am. J. 1976 , 40,  665.
        |  CAS |  open url image1

[48]   Tipping E., Cation Binding by Humic Substances 2002 (Cambridge University: Cambridge, UK).

[49]   G. Berthon , Critical evalution of the stability-constants of metal-complexes of amino-acids with polar side-chains. Pure Appl. Chem. 1995 , 67,  1117.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[50]   B. M. Miskimmin , J. W. M. Rudd , C. A. Kelly , Influence of dissolved organic-carbon, pH, and microbial respiration rates on mercury methylation and demethylation in lake water. Can. J. Fish. Aquat. Sci. 1992 , 49,  17.
        |  CAS | | Crossref | | Crossref |  open url image1

[51]   M. H. Choi , J. J. Cech , M. C. Lagunas-Solar , Bioavailability of methylmercury to Sacramento blackfish (Orthodon microlepidotus): dissolved organic carbon effects. Environ. Toxicol. Chem. 1998 , 17,  695.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[52]   P. R. Gorski , D. E. Armstrong , J. P. Hurley , M. M. Shafer , Speciation of aqueous methylmercury influences uptake by a freshwater alga (Selenastrum capricornutum). Environ. Toxicol. Chem. 2006 , 25,  534.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[53]   P. R. Gorski , D. E. Armstrong , J. P. Hurley , D. P. Krabbenhoft , Influence of natural dissolved organic carbon on the bioavailability of mercury to a freshwater alga. Environ. Pollut. 2008 , 154,  116.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[54]   P. C. Pickhardt , N. S. Fisher , Accumulation of inorganic and methylmercury by freshwater phytoplankton in two contrasting water bodies. Environ. Sci. Technol. 2007 , 41,  125.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed | PubMed |  open url image1

[55]   V. I. Slaveykova , K. J. Wilkinson , Predicting the bioavailability of metals and metal complexes: critical review of the biotic ligand model. Environ. Chem. 2005 , 2,  9.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[56]   A. Boullemant , B. Vigneault , C. Fortin , P. G. C. Campbell , Uptake of neutral metal complexes by a green alga: influence of pH and humic substances. Aust. J. Chem. 2004 , 57,  931.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[57]   B. Vigneault , A. Percot , M. Lafleur , P. G. C. Campbell , Permeability changes in model and phytoplankton membranes in the presence of aquatic humic substances. Environ. Sci. Technol. 2000 , 34,  3907.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[58]   U. Skyllberg , K. Xia , P. R. Bloom , E. A. Nater , W. F. Bleam , Binding of mercury(II) to reduced sulfur in soil organic matter along upland-peat soil transects. J. Environ. Qual. 2000 , 29,  855.
        |  CAS |  open url image1