title: Rate of oxygen isotope exchange between selenate and water.
abstract: The rate of oxygen isotope exchange between selenate and water was investigated at conditions of 10 to 80 °C and pH -0.6 to 4.4. Oxygen isotope exchange proceeds as a first-order reaction, and the exchange rate is strongly affected by reaction temperature and pH, with increased rates of isotope exchange at higher temperature and lower pH. Selenate speciation (HSeO(4)(-) vs SeO(4)(2-)) also has a significant effect on the rate of isotope exchange. The half-life for isotope exchange at example natural conditions (25 °C and pH 7) is estimated to be significantly in excess of 10(6) years. The very slow rate of oxygen isotope exchange between selenate and water under most environmental conditions demonstrates that selenate-δ(18)O signatures produced by biogeochemical processes will be preserved and hence that it will be possible to use the value of selenate-δ(18)O to investigate the biogeochemical behavior of selenate, in an analogous fashion to the use of sulfate-δ(18)O to study the biogeochemical behavior of sulfate.
authors.affiliation: Department of Geological Sciences and Engineering, University of Nevada-Reno, 1664 N. Virginia Street, Reno, Nevada 89557-0138, United States. m_kaneko@jamstec.go.jp
authors.forename: Masanori
authors.initials: M
authors.lastname: Kaneko
authors.forename: Simon R
authors.initials: SR
authors.lastname: Poulson
mesh_terms: D004785:Environmental Pollutants / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010103:Oxygen Isotopes; D064586:Selenic Acid; D018036:Selenium Compounds / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D004785:Environmental Pollutants; D010103:Oxygen Isotopes; D018036:Selenium Compounds; D014867:Water; D064586:Selenic Acid