Understanding the P Chemistry In the Everglades Agricultural Area Canals.

Phosphorus (P) forms and mineral characteristics were investigated in sediments of three EAA main canals Miami, WPB and Ocean in the Everglades Agricultural Area (EAA) in South Florida. The entire EAA is underlain by marl and limestone thus calcium carbonate chemistry was thought to be important in influencing P release/retention in the EAA canals as well. High P concentration in EAA drainage has been attributed to be responsible for the ecosystem changes in the downstream Everglades National Park. Thus understanding the P release/retention mechanisms in these canals is important for effective mitigation and maintenance efforts. Phosphorus fractionation analyses indicated that HCl-P (60-73% of total P) and Residue-P (17-26% of total P) dominated the P fractions in all the canals which indicated P in these canals should be stable. But mineral analysis of the canal sediments by X-ray diffraction and thermogravimetry failed to identify the presence of discrete apatite minerals thereby implying P in these canals to be loosely bound to carbonates that can be subject to release within sediment microzones depending on the ph conditions. Organic matter content varied from 17-43% in the EAA canal sediments, thus organic acids released from the sediment organic matter (17-43%) could be responsible in creating these favorable microzones. Carbonate and organic matter chemistry seem to control the P release/retention mechanisms in the EAA canals.