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

Abstract

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).

The influence of the coagulant PAX-18 on Planktothrix agardhii bloom in a shallow eutrophic fishpond.

“…Differences in phytoplankton abundance between the fishpond and control dealt mainly with its influence on environmental variables in large, deep lakes and phytoplankton communities were usually evaluated only as chlorophyll-a concentrations , GAwrońskA & bRozoWSka 2002. The same situation is in the case of other coagulants , lewAndowski et al 2003, ReitzeL et al 2005. As far as we know, there are no studies focused on the influence of aluminium coagulants on phytoplankton structure in small, shallow fishponds.…”

“…Previous reports on the PAX-18 coagulant have coagulants , lewAndowski et al 2003, ReitzeL et al 2005. In the case of the Bílá Lhota fishpond the PAX-18 coagulant was used for prevention of phosphate release from bottom sediments and removal of phytoplankton organisms from the water column by their coagulation, aggregation and sedimentation.…”

Geo-Engineering in Lakes: A Crisis of Confidence?

“…4 Sequential sediment extractions continue to provide the necessary, standardized information on site specific material-P binding ratios. 1,5 Powerful analytical techniques (e.g., X-ray absorption spectroscopy) are being utilized to provide insights into specific binding mechanisms of the materials with the target chemical species in the presence of confounding constituents (e.g., humic materials). Collectively, these studies highlight the importance of humic substances, Si, pH, alkalinity, and material aging processes in receiving waters and sediments in reducing the binding efficiency and geomorphological stability of various materials.…”

“…(5) Standard protocols for dose determination should be developed based on published literature 5 and knowledge of the likely behavior of the amendment material in the receiving water. (6) The application of materials should be assessed in the context of "dose−response" (i.e., repeated smaller doses) as opposed to the common "single pill" (i.e., single large dose) approach to minimize the risk of unintended consequences.…”

Manipulating nutrient limitation using modified local soils: A case study at Lake Taihu (China)

“…Some conventional geo-engineering materials, such as aluminum-/iron-salts and solid-phase P sorbents (aluminum, iron and lanthanum modified soils/clays etc.) have been tested in fields, which can reduce bioavailable P in water column or sediments (Douglas et al, 2012;Egemose et al, 2010;Lurling and Van Oosterhout, 2013;Reitzel et al, 2005;Robb et al, 2003). However, long-term records of N and P concentrations in 12 large lakes indicate that reducing P consistently is not conductive to N removal (Finlay et al, 2013).…”