Lake restoration by dosing aluminum relative to mobile phosphorus in the sediment.
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).
Reitzel
Kasper
K
Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Hansen
Jonas
J
Andersen
Frede O
FO
Hansen
Kjeld S
KS
Jensen
Henning S
HS
D000535:Aluminum / Q000008:administration & dosage / Q000737:chemistry*; D003718:Denmark; D005618:Fresh Water / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010758:Phosphorus / Q000032:analysis / Q000737:chemistry*; D016062:Porosity; D012621:Seasons; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis*
D014873:Water Pollutants; D010758:Phosphorus; D000535:Aluminum