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Title: Spatial Dependence of Reduced Sulfur in Everglades Dissolved Organic Matter Controlled by Sulfate Enrichment

Authors:
ORCiD logo; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
OTHER U.S. GOVERNMENT
OSTI Identifier:
1351336
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 51; Journal Issue: 7
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Poulin, Brett A., Ryan, Joseph N., Nagy, Kathryn L., Stubbins, Aron, Dittmar, Thorsten, Orem, William, Krabbenhoft, David P., and Aiken, George R. Spatial Dependence of Reduced Sulfur in Everglades Dissolved Organic Matter Controlled by Sulfate Enrichment. United States: N. p., 2017. Web. doi:10.1021/acs.est.6b04142.
Poulin, Brett A., Ryan, Joseph N., Nagy, Kathryn L., Stubbins, Aron, Dittmar, Thorsten, Orem, William, Krabbenhoft, David P., & Aiken, George R. Spatial Dependence of Reduced Sulfur in Everglades Dissolved Organic Matter Controlled by Sulfate Enrichment. United States. doi:10.1021/acs.est.6b04142.
Poulin, Brett A., Ryan, Joseph N., Nagy, Kathryn L., Stubbins, Aron, Dittmar, Thorsten, Orem, William, Krabbenhoft, David P., and Aiken, George R. Wed . "Spatial Dependence of Reduced Sulfur in Everglades Dissolved Organic Matter Controlled by Sulfate Enrichment". United States. doi:10.1021/acs.est.6b04142.
@article{osti_1351336,
title = {Spatial Dependence of Reduced Sulfur in Everglades Dissolved Organic Matter Controlled by Sulfate Enrichment},
author = {Poulin, Brett A. and Ryan, Joseph N. and Nagy, Kathryn L. and Stubbins, Aron and Dittmar, Thorsten and Orem, William and Krabbenhoft, David P. and Aiken, George R.},
abstractNote = {},
doi = {10.1021/acs.est.6b04142},
journal = {Environmental Science and Technology},
number = 7,
volume = 51,
place = {United States},
year = {Wed Mar 15 00:00:00 EDT 2017},
month = {Wed Mar 15 00:00:00 EDT 2017}
}
  • Organic matter isolated from the Florida Everglades caused a dramatic increase in mercury release from cinnabar (HgS), a solid with limited solubility. Hydrophobic (a mixture of both humic and fulvic) acids dissolved more mercury than hydrophilic acids and other nonacid fractions of dissolved organic matter (DOM). Cinnabar dissolution by isolated organic matter and natural water samples was inhibited by cations such as Ca{sup 2+}. Dissolution was independent of oxygen content in experimental solutions. Dissolution experiments conducted in Dl water had no detectable dissolved mercury. The presence of various inorganic (chloride, sulfate, or sulfide) and organic ligands (salicylic acid, acetic acid,more » EDTA, or cysteine) did not enhance the dissolution of mercury from the mineral. Aromatic carbon content in the isolates correlated positively with enhanced cinnabar dissolution. {zeta}-potential measurements indicated sorption of negatively charged organic matter to the negatively charged cinnabar at pH 6.0. Possible mechanisms of dissolution include surface complexation of mercury and oxidation of surface sulfur species by the organic matter.« less
  • Precipitation and aggregation of metacinnabar (black HgS) was inhibited in the presence of low concentrations of humic fractions of dissolved organic matter (DOM) isolated from the Florida Everglades. At low Hg concentrations, DOM prevented the precipitation of metacinnabar. At moderate Hg concentrations, DOM inhibited the aggregation of colloidal metacinnabar At Hg concentrations greater than 5 {times} 10{sup {minus}4} M, mercury formed solid metacinnabar particles that were removed from solution by a 0.1 {micro}m filter. Organic matter rich in aromatic moieties was preferentially removed with the solid. Hydrophobic organic acids inhibited aggregation better than hydrophilic organic acids. The presence of chloride,more » acetate, salicylate, EDTA, and cysteine did not inhibit the precipitation or aggregation of metacinnabar. Calcium enhanced metacinnabar aggregation even in the presence of DOM,m but the magnitude of the effect was dependent on the concentrations of DOM, Hg, and Ca. Inhibition of metacinnabar precipitation appears to be a result of strong DOM-Hg binding. Prevention of aggregation of colloidal particles appears to be caused by adsorption of DOM and electrostatic repulsion.« less
  • The chemical speciation of inorganic mercury (Hg) is to a great extent controlling biologically mediated processes, such as mercury methylation, in soils, sediments, and surface waters. Of utmost importance are complexation reactions with functional groups of natural organic matter (NOM), indirectly determining concentrations of bioavailable, inorganic Hg species. Two previous extended X-ray absorption fine structure (EXAFS) spectroscopic studies have revealed that reduced organic sulfur (S) and oxygen/nitrogen (O/N) groups are involved in the complexation of Hg(II) to humic substances extracted from organic soils. In this work, covering intact organic soils and extending to much lower concentrations of Hg than before,more » we show that Hg is complexed by two reduced organic S groups (likely thiols) at a distance of 2.33 Angstroms in a linear configuration. Furthermore, a third reduced S (likely an organic sulfide) was indicated to contribute with a weaker second shell attraction at a distance of 2.92-3.08 Angstroms. When all high-affinity S sites, corresponding to 20-30% of total reduced organic S, were saturated, a structure involving one carbonyl-O or amino-N at 2.07 Angstroms and one carboxyl-O at 2.84 Angstroms in the first shell, and two second shell C atoms at an average distance of 3.14 Angstroms, gave the best fit to data. Similar results were obtained for humic acid extracted from an organic wetland soil. We conclude that models that are in current use to describe the biogeochemistry of mercury and to calculate thermodynamic processes need to include a two-coordinated complexation of Hg(II) to reduced organic sulfur groups in NOM in soils and waters.« less
  • The binding of Hg{sup 2+} in organic matter of soils and waters controls the transport and transformations of Hg in terrestrial and aquatic ecosystems. The authors developed a competitive complexation method using the strong complexation of Hg{sup 2+} by Br{sup {minus}} for determining the Hg{sup 2+} binding strength in organic soils at native and elevated Hg concentrations. The distribution coefficients determined in KBr suspensions for sorption of native HG{sup 2+} to soil organic carbon (SOC) (K{sub soc}) are in the range of 10{sup 22} to 10{sup 23}. The K{sub soc} significantly decreased with increased additions of Hg{sup 2+} and withmore » decreasing pH. Using data for reduced organic S concentrations determined by x-ray absorption near-edge structure spectroscopy (XANES), the authors calculated surface complex formation constants on the order of 10{sup 32} for a model site having acidity constants of mercaptoacetic acid. This value is in fair agreement with the tabulated value of 10{sup 345} for Hg{sup 2+} binding in mercaptoacetic acid. At native Hg concentrations, formation constants and K{sub soc} values were similar for different types of soil organic matter along transects from uplands into wetlands, despite varying concentration of Hg and reduced organic S. Their adsorption data are consistent with the conclusions from their previous extended x-ray absorption fine structure spectroscopy (EXAFS) study that in a humic acid and soil, Hg{sup 2+} ions bond in two-fold coordination involving one reduced S and one O or N.« less