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Lake Restoration by Dosing Aluminum Relative to Mobile Phosphorus in the Sediment

2005; American Chemical Society; Volume: 39; Issue: 11 Linguagem: Inglês

10.1021/es0485964

1520-5851

Kasper Reitzel, Jonas Hansen, Frede Østergaard Andersen, Kjeld Hansen, Henning S. Jensen,

Phosphorus and nutrient management

In the sediment of the shallow, hypertrophic Lake Sønderby, Denmark, potentially mobile phosphorus (Pmobile) was determined by a sequential extraction technique as the sum of porewater P, iron-bound P, and nonreactive P (i.e., polyphosphates and organic P). A good agreement was observed between loss rates of Pmobile in the top 10 cm of the sediment from winter to summer, P release rates measured in undisturbed sediment cores, and rates of P accumulation in the lake water from winter to summer (22, 32, and 30 mg of P m-2 day-1, respectively). This suggests that the operationally defined Pmobile was the sediment P fraction responsible for the internal loading in the lake. In autumn 2001, 11 mg of aluminum (Al) L-1, equivalent to 31 g of Al m-2, was added to the lake water. This dosage represented a 4:1 molar ratio between Al and Pmobile. The Al treatment significantly decreased lake water P, and P precipitated from the lake water was recovered as Al-bound P in the sediment after the treatment. Internal P loading was reduced by 93% in the two posttreatment years, relative to 2001. Accordingly, average summer concentrations of total P in lake water declined from 1.28 (SE = 0.17) and 1.3 (SE = 0.14) mg L-1 in the two pretreatment years to 0.09 (SE = 0.01) and 0.13 (SE = 0.01) mg L-1 in the posttreatment years. pH levels remained unchanged relative to pretreatment levels, while the total alkalinity was reduced from 3.2 (SE = 0.04) to 2.7 (SE = 0.03) mequiv L-1.