Phosphorus Sequestration in Lake Sediment with Iron Mine Tailings

Abstract

Internal phosphorus loading can lead to eutrophication in lakes when anoxic sediments release bioavailable phosphorus into the water column. In laboratory experiments, iron mine tailings helped to sequester phosphorus in sediment from a eutrophic lake. Phosphorus release from the sediments after extraction with distilled water or 0.02 N H ₂ SO ₄ was significantly reduced when mine tailings were added (1:1 w/w), even when the system was anaerobic (∼ 1 mg O ₂ /L). The degree of sequestration was enhanced when glucose (1% w/w) was added to stimulate the growth of microorganisms, suggesting that the process was microbially mediated. We suggest that oxidized iron in the mine tailings served as an electron sink for microbial respiration via dissimilatory Fe³⁺ reduction. The reduced iron released into solution sequestered phosphorus, either as it re-oxidized and formed hydrous ferric oxide complexes containing phosphorus (HFO-P), or through precipitation. Since mine tailings are inexpensive, they may prove useful for preventing phosphorus from entering surface waters, as well as reducing internal phosphorus loading.

Keywords:

• Nutrients
• phosphorus
• lakes
• wetlands
• soil
• remediation
• sequestration.

Acknowledgements

The authors appreciate constructive comments on the manuscript from M. Iqbal, K. Dhanwada, A. Schwemm and three anonymous reviewers. This study was funded by the Roy J. Carver Charitable Trust, the Iowa Space Grant Consortium, the Iowa State Water Resources Research Institute and Environmental Programs at the University of Northern Iowa. S. Liegeois was supported by an exchange program between UNI and the Ecole Nationale Supérieure de Chimie de Rennes, France.