Oxidation-Reduction Reactions

Oxidation-reduction or ‘redox reactions’ involve a transfer of electrons, and cause changes in the oxidation state of both the reactants and the products. Oxidation is the loss of electrons and reduction is the gain of electrons. Redox reactions are important in marine systems because the chemical properties of many elements change depending on their oxidation state: for example sulphate (SO₄^2-) and hydrogen sulfide gas (H₂S) formed by sulfate reduction have very different physical, chemical and ecotoxological properties.The redox condition of a solution is usually expressed in terms of pE, which is dimensionless, or Eh which is measured in volts.