ENVR 31 |
| Postglacial oxidation processes in young clayey soils and sediments have used up the inherited content of reduced iron compounds, e.g., exchangeable ferrous iron, structural ferrous iron in clay minerals and pyrite. Normally, the oxidized brownish colored zone reaches down to depths of 3 to 7 meters below the surface. In the oxidized zone renewal of ferrous iron is restricted to microenvironments around bioavailable organic carbon leached from the surface. Below arable land, nitrate occurs in high concentrations in the oxidized zone. An efficient reduction of nitrate takes place in the suboxic zone (thickness < 0.5 meter) characterized by mixed mineralogical composition of ferrous and ferric iron, located just above the reduced grayish colored zone. The oxidation processes in these soils and sediments promote the downward progression of nitrate. On the other hand, contemporary formation of iron oxides retards other often used agrochemicals, e.g., glyphosate and phosphorus. |
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Microbially Mediated Redox Dynamics in the Shallow Subsurface
1:30 PM-4:10 PM, Sunday, 10 September 2006 Moscone Center -- Room 202/204, Oral
Division of Environmental Chemistry |