Sediment amendment with Phoslock in Clatto Reservoir (Dundee, UK): investigating changes in sediment elemental composition and phosphorus fractionation

Meis, Sebastian; Spears, Bryan M.; Maberly, Stephen C.; O'Malley, Michael B.; Perkins, Rupert G.. 2012 Sediment amendment with Phoslock in Clatto Reservoir (Dundee, UK): investigating changes in sediment elemental composition and phosphorus fractionation. Journal of Environmental Management, 93 (1). 185-193. 10.1016/j.jenvman.2011.09.015

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Abstract/Summary

Lanthanum-modified bentonite clay (Phoslock®) is a lake remediation tool designed to strip dissolved phosphorus (P) from the water column and increase the sediment P-sorption capacity. This study investigated short term alterations in sediment elemental composition and sediment P-fractions based on sediment cores taken 2 days before and 28 days following the application of 24 t of Phoslock® to a 9 ha, man-made reservoir. Following the application, sediment lanthanum (La) content increased significantly (p < 0.05; n = 4) in the top 8 cm of the sediment, thereby theoretically increasing sediment P-binding capacity on the whole reservoir scale by 250 kg. Mass balance calculations were used to estimate the theoretical binding of release-sensitive P (Pmobile; sum of ‘labile P’, ‘reductant-soluble P’ and ‘organic P’ fraction) by La across the top 4 cm and 10 cm depth of sediment. The amended mass of La in the sediment had the potential to bind 42% of Pmobile present in the top 4 cm or 17% of Pmobile present in the top 10 cm. However, with the exception of a significant increase (p < 0.05; n = 4) in the ‘residual P’ fraction in the top 2 cm, sediment P-fractions, including Pmobile, did not differ significantly following the Phoslock® application. Experimental P-adsorption studies indicated P-saturation values for Phoslock® of 21,670 mg P kg−1 Phoslock®. Sequential extraction of P from saturated Phoslock® under laboratory conditions indicated that around 21% of P bound by Phoslock® was release-sensitive, while around 79% of bound P was unlikely to be released under reducing or common pH (5–9) conditions in shallow lakes. Applying Phoslock® is, therefore, likely to increase the P-sorption capacity of sediments under reducing conditions.

Item Type:	Article
Identification Number/DOI:	10.1016/j.jenvman.2011.09.015
Programmes:	CEH Topics & Objectives 2009 onwards > Water > WA Topic 3 - Science for Water Management > WA - 3.4 - Develop novel and improved methods to enable the sustainable management of freshwaters and wetlands
CEH Sections:	Parr Watt
ISSN:	0301-4797
Additional Keywords:	internal loading, remediation, whole-lake, phosphorus fractions, Phoslock®
NORA Subject Terms:	Ecology and Environment
Date made live:	15 Dec 2011 13:52
URI:	http://nora.nerc.ac.uk/id/eprint/16157

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