Soil processes and trace metals

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Presentation transcript:

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

Metal mobility & sorption in soils IP Formation of hydrolysis species Soil Fe/Al/Mn oxides OM Environments pH pe

Concentrations of trace metals in equilibrium solutions of sandy Spodisols Precipitation hydrolysis Cu Pb The best way to draw the lines? Kabata-Pendias and Pendias (1992)

Precipitation/hydrolysis logk Cu2+ + 2H2O  Cu(OH)2 + 2H+ -8.68 Cu2+ + H2O  CuOH- + H+ -7.70 Cu2+ + 2H2O  Cu(OH)2 + 2H+ -13.8 Log (Cu2+) = log k – 2 pH Log (CuOH-) = log k + log (Cu2+) + pH Log (Cu(OH)2) = log k + log (Cu2+) + 2 pH

Solubility of hydrous oxide (Lindsay, 1979) Cd(OH)2 + 2H+  Cd2+ + 2H2O 13.7 Zn(OH)2 + 2H+  Zn2+ + 2H2O 11.8 Cu(OH)2 + 2H+  Cu2+ + 2H2O 8.68 Pb(OH)2 + 2H+  Pb2+ + 2H2O 8.16 Cd2+ + H2O  CdOH+ + H+ -10.1/-20.3 Cu2+ + H2O  CuOH+ + H+ -7.70/-13.8 Pb2+ + H2O  PbOH+ + H+ -7.70/-17.8 Zn2+ + H2O  ZnOH+ + H+ -7.69/-16.8 Stability of hydrolysis species (Lindsay, 1979)

Kabata-Pendias and Pendias (1992)

Mobility of metals as influenced by soil pH Cd 8.0-9.5 Cu 5.4-6.9 Pb 7.2-8.7 Zn 5.2-8.3 Fe3+ 2.2-3.2 Cr3+ 4.6-5.6 Al3+ 3.8-4.8 pH of hydrous oxide formation Kabata-Pendias and Pendias (1992)

Sposito, 1984

Siegel, 2002 pH<6: Cd mobility increases pH<5: Zn mobility increases All except Mn and Ni are chalcophile elements Siegel, 2002