Aswin Kottapurath Vijay

Iron(II), (Fe(H 2 O) 6 2+ , (Fe II ) participates in many reactions of natural and biological importance. It is critically important to understand the rates and the mechanism of Fe II oxidation by dissolved molecular oxygen, O 2 , under environmental conditions containing bicarbonate (HCO 3 − ), which exists up to millimolar concentrations. In the absence and presence of HCO 3 − , the formation of reactive oxygen species (O 2 ⋅ − , H 2 O 2 , and HO⋅) in Fe II oxidation by O 2 has been suggested. In contrast, our study demonstrates for the first time the rapid generation of carbonate radical anions (CO 3 ⋅ − ) in the oxidation of Fe II by O 2 in the presence of bicarbonate, HCO 3 − . The rate of the formation of CO 3 ⋅ − may be expressed as d[CO 3 ⋅ − ]/dt=[Fe II [[O 2 ][HCO 3 − ] 2 . The formation of reactive species was investigated using 1 H nuclear magnetic resonance ( 1 H NMR) and gas chromatographic techniques. The study presented herein provides new insights into the reaction mechanism of Fe II oxidation by O 2 in the presence of bicarbonate and highlights the importance of considering the formation of CO 3 ⋅ − in the geochemical cycling of iron and carbon.