With 9 figures and 2 tables ,

No abstract

The distribution of sediment physical characteristics, sediment phosphorus (P) pools, and laboratory-based rates of P release from the sediments were used to identify regions and dosage for alum treatment in Wind Lake, Wisconsin. Using variations in sediment moisture content, we identified an erosional zone at depths < 1.4 m and an accumulation zone at depths > 2.6 m.Mean concentrations of porewater P, loosely-bound P, iron-and aluminum-bound P, and mean rates of P release from sediments under anoxic conditions were high in the accumulation zone compared to sediment P characteristics in the erosional zone, indicating focusing of readily mobilized sediment P pools from shallow regions and accumulation to deep regions. We determined that a future alum treatment for control of internal P loading would be most effective at depths > 2.6 in the accumulation zone. The mean rate of anoxic P release from sediments encountered in the accumulation zone (8.3 mg m-2 d') was used in conjunction with a summer anoxic period of 122 d, and a treatment area of 1.6 km2 to estimate an internal P load of 1,600 kg to be controlled. Our results suggest that an understanding of the distribution of sediment P pools and P fluxes in lakes provides a strategy for estimating alum dosage and application areas. (KEY TERMS: alum treatment; focusing; internal phosphorus loading; phosphorus; sediment; sediment phosphorus fractions.)