Reassessment of the performance of mineral-based sediment capping materials to bind phosphorus: a comment on Akhurst et al. (2004)

Abstract

The understanding and management of eutrophication leading to troublesome algal blooms is pivotal to the health of aquatic systems. There are also considerable economic implications. Algal blooms in Australia cost between A$180 and 240 million dollars per annum (Atech 2000). Initial strategies to control phosphorus (P) supply as a limiting nutrient for algal growth centred on the reduction of point sources and the manipulation of water-column oxygen. In the past decade, however, mineral-based amendments have been recognised for their potential to bind P under a range of physico-chemical conditions (e.g. Douglas et al. 2004). Akhurst et al. (2004) examined the performance of two mineral-based materials to treat P-enriched water and/or sediment. The first was Bauxsol, a red mud–seawater derivative, presumably similar to the seawater amendment of red mud originally described in Thornber and Hughes (1987). The second material was a lanthanum (La)-modified bentonite. We address two major issues: