Journal
WATER RESEARCH
Volume 125, Issue -, Pages 191-200Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2017.08.044
Keywords
Restoration; Phoslock; Lanthanum; Geoengineering; Lake
Funding
- Villum Kann Rasmussen Centre of Excellence: Centre for Lake Restoration (CLEAR)
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A 12 days laboratory study on potential desorption of Lanthanum (La) from a commercial La modified clay (Phoslock) was conducted using lake water from 17 Danish lakes with alkalinities between 0.02 and 3.7 meq L-1 and varying concentrations of DOC and humic acids (HA's). A similar study was conducted in artificial lake water with alkalinities from 0 to 2.5 meq L-1 order to exclude interference from dissolved HA's. To test if La in solution (FLa) was associated with fine particles, the water samples were filtered sequentially through three filter sizes (1.2 mu m, 0.45 mu m and 0.2 mu m), and finally, ultracentrifugation was used in an attempt to separate colloidal La from dissolved La. The study showed that higher FLa (up to 2.5 mg L-1 or 14% of the total La in the Phoslock) concentrations were found in soft water lakes compared to hard water lakes, probably due to dispersion of the clay at low alkalinities. In addition, this study showed that HA's seem to increase the FLa concentrations in soft water lakes, most likely through complexation of La retained in the Phoslock matrix. In summary, we conclude that elevated La concentrations in lake water after a Phoslock treatment should only be expected in soft water lakes rich in DOC and HA's. (C) 2017 Elsevier Ltd. All rights reserved.
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