title: Humic substances interfere with phosphate removal by Lanthanum modified clay in controlling eutrophication.
abstract: The lanthanum (La) modified bentonite Phoslock(®) has been proposed as dephosphatisation technique aiming at removing Filterable Reactive Phosphorus (FRP) from the water and blocking the release of FRP from the sediment. In the modified clay La is expected the active ingredient. We conducted controlled laboratory experiments to measure the FRP removal by Phoslock(®) in the presence and absence of humic substances, as La complexation with humic substances might lower the effectiveness of La (Phoslock(®)) to bind FRP. The results of our study support the hypothesis that the presence of humic substances can interfere with the FRP removal by the La-modified bentonite. Both a short-term (1 d) and long-term (42 d) experiment were in agreement with predictions derived from chemical equilibrium modelling and showed lower FRP removal in presence of humic substances. This implies that in DOC-rich inland waters the applicability of exclusively Phoslock(®) as FRP binder should be met critically. In addition, we observed a strong increase of filterable La in presence of humic substances reaching in a week more than 270 μg La l(-1) that would infer a violation of the Dutch La standard for surface water, which is 10.1 μg La l(-1). Hence, humic substances are an important factor that should be given attention when considering chemical FRP inactivation as they might play a substantial role in lowering the efficacy of metal-based FRP-sorbents, which makes measurements of humic substances (DOC) as well as controlled experiments vital.
authors.affiliation: Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands; Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB Wageningen, The Netherlands. Electronic address: miquel.lurling@wur.nl.
authors.forename: Miquel
authors.initials: M
authors.lastname: Lürling
authors.affiliation: Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands; Regional Water Authority Brabantse Delta, P.O. Box 5520, 4801 DZ Breda, The Netherlands.
authors.forename: Guido
authors.initials: G
authors.lastname: Waajen
authors.affiliation: Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
authors.forename: Frank
authors.initials: F
authors.lastname: van Oosterhout
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D002244:Carbon / Q000032:analysis; D011232:Chemical Precipitation; D000077215:Clay; D004553:Electric Conductivity; D005068:Eutrophication; D005374:Filtration; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007811:Lanthanum / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry; D008956:Models, Chemical; D010710:Phosphates / Q000302:isolation & purification*; D010758:Phosphorus / Q000032:analysis; D013535:Suspensions; D013997:Time Factors
chemical_list: D000538:Aluminum Silicates; D006812:Humic Substances; D008903:Minerals; D010710:Phosphates; D013535:Suspensions; C003004:rhabdophane; D010758:Phosphorus; D007811:Lanthanum; D002244:Carbon; D000077215:Clay
keywords: DOC; Eutrophication control; Lake management; Lake restoration; Lanthanum modified clay; Phoslock(®)