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 has been proposed that ferric chloride addition to agricultural runoff entering the northern Everglades could provide a means for enhancing natural mechanisms of phosphorus removal from the wetland. In this study we added ferric chloride to Everglades water spiked with 32PO4, incubating the resulting precipitates in microcosms simulating the Everglades ecosystem. 32P activity and reduction-oxidation (redox) potentials were monitored to determine if the 32P was released into the overlying water column due to iron reduction. Results of redox potential measurements and 32P activity indicate that although reducing conditions exist in the soil, on average less than 1% of the added 32P was measured in the water column during the 139-day incubation. Ferric chloride addition thus might prove an effective means of long-term phosphorus retention in the Florida Everglades and perhaps other wetland systems.