Transcript Slide 1

Electrical Potential
Generated by the
Iron Cycle
Air
O2 O2
Water
+
H2HO2O
Sediment
Fe3+
Fe3+
eFe2+
2H+
2H+
Organic Matter
e-
eCO2
-
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The oxidation of organic matter to CO2 by bacteria in the anaerobic zones of sediment produces an excess of reactive
electrons at the bottom of the column. Some of these electrons are transferred directly to the bottom electrode (anode). Others
are used by bacteria to reduce Fe3+ to Fe2+. This reduced iron can then be oxidized back to Fe3+ at the anode which takes up
the extra electron. The presence of oxygen at the top of the column causes a deficit of electrons. The difference between
concentrations of electrons at the top and bottom of the column produces an electrical potential or charge. We can measure
the potential by connecting the top and bottom electrodes. The electrons at the anode will flow to the cathode where they will
react with oxygen to form water. Potential is measured in volts and the rate of flow (current) is measured in amps.