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Isotope Studies of the Sulfur Cycling using the Four Sulfur Isotopes: Developing Tools to Investigate the Flow of Sulfur through Biogeochemical Systems

Periodic Report Summary - SULFUTOPES (Isotope Studies of the Sulfur Cycling using the Four Sulfur Isotopes: Developing Tools to Investigate the Flow of Sulfur through Biogeochemical Systems)

During last 12 months of the project execution, Wadden Sea sediments and tidal flat sulfide-rich water pools were sampled for studying their biogeochemistry by combination of quantitative and isotopic techniques. Concentrations of sulfate, sulfide, elemental sulfur and thiosulfate as well as quadruple sulfur isotope composition of both, main (sulfate and sulfide) and intermediate (zero-valent sulfur) species were measured.

Analyses of quadruple sulfur isotope composition of samples acquired in the first two years of the project execution (Yellowstone National Park hydrothermal springs and Delaware Great Marsh pore-waters) were continued during two visits to the University of Maryland, 7 - 10 days each. Unexpected detection of high concentrations of hydrogen cyanide (up to 1.92 µmol l-1 of free and 6.94 µmol l-1 of strong metallo-complexed cyanide) and thiocyanate (up to 2.28 µmol l-1 of free thiocyanate) in the Delaware Great Marsh pore waters led to a collateral research. This research resulted in clarification of cyanide source and sinks in the salt marsh. I found that hydrogen cyanide is produced by the roots of cord grass Spartina alterniflora. The main sinks of free hydrogen cyanide were found to be complexation with Fe(II), adsorption on sediment and especially the reaction with zero-valent sulfur species. This reaction results in formation of thiocyanate, which is less toxic than hydrogen cyanide.

Four papers based on results obtained during previous years were submitted to international peer-reviewed journals. One paper was published in Geochimica et Cosmochimica Acta, two of them were accepted for publication in Marine Chemistry and one was accepted for publication in International Journal of Environmental Analytical Chemistry. Significant part of the work time in the last 12 months of project period was focused on acquiring of academic position. From 1 August 2011 I was received tenure-track senior lecturer position at the Ben-Gurion University of the Negev, Beer Sheva, Israel.