Inorganic phosphorus chemistry of Utah Lake's effluent mixing zones

Abstract

While restoration efforts for eutrophic lakes often target point sources containing high concentrations of total phosphorus, Utah Lake may present a challenging case wherein restoration efforts could be potentially overwhelmed by the loading and cycling of phosphorus in the lake. The effects of wastewater phosphorus on the effluent mixing zones of Utah Lake were investigated through water and sediment analyses, including mixing experiments, geochemical modeling, batch desorption, sequential extraction, and x-ray diffraction. Under the given experimental conditions, soluble reactive phosphorus appears to remain stable while in transit to the lake. Geochemical models indicate that calcite is the only major mineral precipitating in Utah Lake. Although redox-sensitive minerals can temporarily retain phosphorus, the only inorganic sedimentation mechanism that may permanently render phosphorus biologically unavailable in this system is the coprecipitation of phosphate with calcite. Quantifying these mechanisms will become an essential aspect of characterizing total phosphorus cycling in Utah Lake.