Speciation of Polysulfides and Zerovalent Sulfur in Sulfide-rich Water Wells in Southern and Central Israel |
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Authors: | Jr" target="_blank">A KamyshnyJr M Zilberbrand I Ekeltchik T Voitsekovski J Gun O Lev |
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Institution: | (1) Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, Bremen, 28359, Germany;(2) Research Division, Hydrological Service of Israel, P.O. Box 36118, Jerusalem, 91360, Israel;(3) Laboratory of Environmental Chemistry, The Casali Institute of Applied Chemistry, The Chemistry Institute, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel |
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Abstract: | Zerovalent sulfur and inorganic polysulfides were determined in nine sulfide-rich water wells in central and southern Israel.
Although the two locations belong to the same aquifer, they are characterized by different pH and hydrogen sulfide levels.
Hydrogen sulfide in the central Israel wells ranged between 19 and 32 μM, and the pH was 7.26 ± 0.07. The southern basin is
characterized by lower water circulation, lower pH (around 6.8), and higher hydrogen sulfide levels (>470 μM). Polysulfides
were determined by a rapid single-phase methylation using methyl trifluoromethanesulfonate (methyl triflate) reagent. The
summary polysulfide concentration for S42−–S72− species was found to be around 0.14–0.75 μM in the central region of Israel and substantially higher, 2.3–4.6 μM in the southern
region. The sum of polysulfide zerovalent sulfur and colloidal sulfur was quantitatively detected by cyanide derivatization
and compared to polysulfide sulfur determined by methyl triflate derivatization and to the chloroform extraction of zerovalent
sulfur. A method for the determination of sulfur undersaturation level—the ratio between dissolved elemental sulfur and its
equilibrium concentration in the presence of solid sulfur—based on the observed levels of the major polysulfide species is
described. The observed polysulfide speciation was compared with the predicted speciation under sulfur saturation conditions
taking into account the water temperature, its ionic strength, and pH. Criteria for sulfur saturation versus unsaturated conditions
were established based on (1) the chain length dependence of the ratio between the observed polysulfide concentrations and
their predicted value under sulfur saturated conditions, and (2) the difference between the concentration of zerovalent sulfur,
as determined by cyanolysis, and the total polysulfide sulfur. According to this dual criterion five of the water wells were
classified as being undersaturated with respect to sulfur, though for all the examined water wells the majority of the zerovalent
sulfur was in the form of polysulfide sulfur. |
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Keywords: | Inorganic polysulfides Sulfide Speciation Methyl trifluoromethanesulfonate Methylation Derivatization Reduced sulfur compounds Dimethylpolysulfanes |
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