SUPPLY OF PHOSPHORUS TO THE WATER COLUMN OF A PRODUCTIVE HARDWATER LAKE - CONTROLLING MECHANISMS AND MANAGEMENT CONSIDERATIONS

Onondaga Lake is a hypereutrophic, industrially polluted lake located in Syracuse, NY. High hypolimnetic concentrations of H2S that develop after anoxia restrict the accumulation of total Fe2+ due to the format ion of FeS, and may limit Fe-PO4 interactions. High water column conce ntrations of Ca2+ and high rates of CaCO3 deposition occur due to inpu ts of Ca2+ from an adjacent soda ash manufacturing facility. Patterns of P concentration and other water chemistry parameters in the lower w aters, and results from chemical equilibrium calculations, suggest tha t Ca-PO4 minerals may regulate the supply of P from sediments to the w ater column in Onondaga Lake. These findings have important management implications for Onondaga Lake. First, declines in water column Ca2concentrations due to reductions in industrial CaCl2 input may result in conditions of undersaturation with respect to Ca-PO4 mineral solubi lity and increases in the release of P from sediments to the water col umn. Second, introduction Of O2 from hypolimnetic oxygenation, as a la ke remediation initiative, may enhance P supply from sediments, becaus e of increased solubility of Ca-PO4 minerals at lower pH.