Soil processes and trace metals Have some ideas about metal concentrations in soils Get familiar with FDEP Soil Cleanup Target Levels and regulations by different countries Background metal concentrations in Florida soils Factors controlling metal behaviors in soils

Typical Eh in soils: -0.4 to 0.7 Pe=16.9 Eh = -2.1 Adding metallic iron to protect Pb corrosion?? Typical Eh in soils: -0.4 to 0.7

Fig. 2.1 Equilibrium redox relationships of aqueous systems. The inscribed area is representative of most soils pH: 4 to 9 pe: -4 to 12 Eh: -0.3 to 0.7 Sb= +110 Pb= -130 Pe = 16.9 E Fe= -440 Lindsay (1979)

Possible Lead Reactions in Soils Pb + O2 + 2H+ + 2e- --Oxidation--> PbO  + H2O CO2 + H2O --carbonation--> H2CO3 --> H+ + HCO3- PbO + H2CO3 --precipitation--> PbCO3  + H2O PbCO3 --dissolution--> Pb2+ + CO32- 3Pb2+ + 2CO32- + 2OH---precipitation-->Pb3(CO3)2(OH)2

Possible Lead Reactions in Soils Pb + O2 + 2H+ + 2e- --Oxidation--> PbO  + H2O CO2 + H2O --carbonation--> H2CO3 --> H+ + HCO3- PbO + H2CO3 --precipitation--> PbCO3  + H2O PbCO3 --dissolution--> Pb2+ + CO32- 3Pb2+ + 2CO32- + 2OH---precipitation-->Pb3(CO3)2(OH)2