Iron Reduction and Phosphorus Release from Lake Sediments and Bt Horizon Soil: Incubation Studies to Explore Phosphorus Cycling

Sediment from two Georgia Piedmont impoundments and soil from the Georgia Piedmont Bt horizon were incubated with an easily consumable organic carbon substrate in an anaerobic environment to observe iron reduction and phosphorus release. 97% of porewater iron in the Bt horizon soil, 96% of porewater iron in Lake Lanier sediments, and 93% of porewater iron in Lake Oglethorpe sediments was reduced to a soluble form during anaerobic incubation. Phosphorus release followed a similar trend with 83% of total P in Bt horizon porewaters, 77% of total P in Lake Lanier sediment porewater, and 61% of total P in Lake Oglethorpe sediment porewater solubilized. The iron reduction and phosphorus release observed in soil from the Bt horizon collected in the Piedmont region of Georgia indicates that phosphorus transported to Piedmont impoundments may be made biologically available through iron reduction in the sediments. The smaller percentage of P and Fe solubilized in Lake Oglethorpe sediments may indicate that there is less reducible iron in these sediments, and that less P is directly adsorbed or bound to oxidized iron and thus less available for release upon iron reduction. We discuss the implications this work has on lake and watershed management practices in the Georgia Piedmont.