Stability of phosphorus within a wetland soil following ferric chloride treatment to control eutrophication

Addition of iron and aluminum compounds has become an increasingly popular method to regulate phosphorus eutrophication in lakes and reservoirs. It ha s been proposed that ferric chloride addition to agricultural runoff enteri ng the northern Everglades could provide a means for enhancing natural mech anisms of phosphorus removal from the wetland. In this study we added ferri c chloride to Everglades water spiked with (PO4)-P-32, incubating the resul ting precipitates in microcosms simulating the Everglades ecosystem. P-32 a ctivity and reduction-oxidation (redox) potentials were monitored to determ ine if the P-32 was released into the overlying water column due to iron re duction. Results of redox potential measurements and P-32 activity indicate that although reducing conditions exist in the soil, on average less than 1% of the added P-32 was measured in the water column during the 139-day in cubation. Ferric chloride addition thus might prove an effective means of l ong-term phosphorus retention in the Florida Everglades and perhaps other w etland systems.