Effectiveness of Al, Ca, and Fe salts for control of internal phosphorus loading in shallow and deep lakes

Abstract

Internal P loading can maintain high P concentrations and delay eutrophic lake recovery following abatement of external loading. Sediment P inactivation with Al salts has been shown to provide long- term (5-14 years) control of sediment P release; long-term effectiveness of Fe and Ca salts has not been reported. Al toxicity problems are possible unless pH is maintained in the 6-8 range. Vertical transport of hypolimnetic P is unlikely in small, deep, dimictic lakes (zJA;;> 8), and effectiveness of P inacti- vation in lowering their mid-summer epilimnetic P has not been demonstrated. To date, P inactivation has been found to be most effective in improving trophic state in shallow, softwater, polymictic lakes where control of sediment P release affects the entire water column. Abatement of external loading, where necessary, is essential for a successful P inactivation treatment.