Time filter

Source Type

Ottersberg, Germany

Dithmer L.,University of Southern Denmark | Nielsen U.G.,University of Southern Denmark | Lurling M.,Wageningen University | Spears B.M.,UK Center for Ecology and Hydrology | And 5 more authors.
Water Research | Year: 2016

A combined field and laboratory scale study of 10 European lakes treated between 2006 and 2013 with a lanthanum (La) modified bentonite (LMB) to control sediment phosphorus (P) release was conducted. The study followed the responses in sediment characteristics including La and P fractions and binding forms, P adsorption capacity of discrete sediment layers, and pore water P concentrations. Lanthanum phosphate mineral phases were confirmed by solid state 31P MAS NMR and LIII EXAFS spectroscopy. Rhabdophane (LaPO4 · nH2O) was the major phase although indications of monazite (LaPO4) formation were also reported, in the earliest treated lake. Molar ratios between La and P in the sediments were generally above 1, demonstrating excess La relative to P. Lanthanum was vertically mixed in the sediment down to a depth of 10 cm for eight of the ten lakes, and recovery of La in excess of 100% of the theoretical aerial load indicated translocation of the LMB towards the deepest areas of the lakes. Lanthanum was generally recovered from bed sediment samples following sequential chemical extraction from the HCl fraction. Soluble reactive P (SRP) release experiments on intact sediment cores indicated conditions of P retention (with the exception of two lakes) by sediments, indicating effective control of sediment P release, i.e. between two and nine years after treatment. © 2016 Elsevier Ltd.

Spears B.M.,UK Center for Ecology and Hydrology | Lurling M.,Environmental Quality Management | Lurling M.,Netherlands Institute of Ecology | Yasseri S.,Institute Dr Nowak | And 8 more authors.
Water Research | Year: 2013

Phoslock® is a lanthanum (La) modified bentonite clay that is being increasingly used as a geo-engineering tool for the control of legacy phosphorus (P) release from lake bed sediments to overlying waters. This study investigates the potential for negative ecological impacts from elevated La concentrations associated with the use of Phoslock® across 16 case study lakes. Impact-recovery trajectories associated with total lanthanum (TLa) andfilterable La (FLa) concentrations in surface and bottom waters were quantified over aperiod of up to 60 months following Phoslock® application. Both surface and bottomwaterTLa and FLa concentrations were <0.001mgL-1 in all lakes prior to the application ofPhoslock®. The effects of Phoslock® application were evident in the post-applicationmaximum TLa and FLa concentrations reported for surface waters between 0.026mgL-1-2.30mgL-1 and 0.002mgL-1 to 0.14mgL-1, respectively. Results of generalised additive modelling indicated that recovery trajectories for TLa and FLa in surface and bottom waters in lakes were represented by 2nd order decay relationships, with time, and that recovery reached an end-point between 3 and 12 months post-application. Recovery in bottom water was slower (11-12 months) than surface waters (3-8 months), most probably as a result of variation in physicochemical conditions of the receiving waters and associated effects on product settling rates and processes relating to the disturbance of bed sediments. CHEAQS PRO modelling was also undertaken on 11 of the treated lakes in order to predict concentrations of La3+ ions and the potential for negative ecological impacts. This modelling indicated that the concentrations of La3+ ions will be very low (<0.0004mgL-1) in lakes of moderately low to high alkalinity (>0.8mEqL-1), but higher (up to 0.12mgL-1) in lakes characterised by very low alkalinity. The effects of elevated La3+ concentrations following Phoslock® applications in lakes of very low alkalinity requires further evaluation. The implications for the use of Phoslock® in eutrophication management are discussed. © 2013 Elsevier Ltd.

Ebert J.,Institute Dr Nowak | Poltrock U.,Nordzucker AG Braunschweig | Preuss T.,Nordzucker AG Werk Uelzen | Fauter K.,Nordzucker AG Braunschweig
Zuckerindustrie | Year: 2012

As part of annual physical examinations at Nordzucker's Uelzen facility, before stored beets were applied to the land, elevated contents (>1 mg/kg dry substance) of toluene were detected. To identify the cause and possible sources, extensive studies were performed during the campaign of 2011/12. The results showed that toluene neither occurs - nor is it introduced - at any point during the manufacturing process. Through laboratory and field experiments, intermediate microbiological formation of toluene was detected under anaerobic conditions in the stored beet sediment. The recycling of beet soil on agricultural land continues to occur despite this intermediate toluene formation, which is still considered to be within the existing guidelines and legal requirements for environmental and chemical safety.

Mackay E.B.,UK Center for Ecology and Hydrology | Maberly S.C.,UK Center for Ecology and Hydrology | Pan G.,CAS Research Center for Eco Environmental Sciences | Reitzel K.,University of Southern Denmark | And 14 more authors.
Inland Waters | Year: 2014

The use of geoengineering techniques for phosphorus management offers the promise of greater and quicker chemical and ecological recovery. It can be attractive when used with other restoration measures but should not be considered a panacea. The range of materials being proposed for use as well as the in-lake processes targeted for manipulation continues to grow. With increasing political imperatives to meet regulatory goals for water quality, we recommend a coordinated approach to the scientific understanding, costs, and integration of geoengineering with other approaches to lake management. © International Society of Limnology 2014.

Spears B.M.,UK Center for Ecology and Hydrology | Mackay E.B.,UK Center for Ecology and Hydrology | Yasseri S.,Institute Dr Nowak | Gunn I.D.M.,UK Center for Ecology and Hydrology | And 13 more authors.
Water Research | Year: 2015

Lanthanum (La) modified bentonite is being increasingly used as a geo-engineering tool for the control of phosphorus (P) release from lake bed sediments to overlying waters. However, little is known about its effectiveness in controlling P across a wide range of lake conditions or of its potential to promote rapid ecological recovery. We combined data from 18 treated lakes to examine the lake population responses in the 24 months following La-bentonite application (range of La-bentonite loads: 1.4-6.7 tonnes ha-1) in concentrations of surface water total phosphorus (TP; data available from 15 lakes), soluble reactive phosphorus (SRP; 14 lakes), and chlorophyll a (15 lakes), and in Secchi disk depths (15 lakes), aquatic macrophyte species numbers (6 lakes) and aquatic macrophyte maximum colonisation depths (4 lakes) across the treated lakes. Data availability varied across the lakes and variables, and in general monitoring was more frequent closer to the application dates. Median annual TP concentrations decreased significantly across the lakes, following the La-bentonite applications (from 0.08 mg L-1 in the 24 months pre-application to 0.03 mg L-1 in the 24 months post-application), particularly in autumn (0.08 mg L-1 to 0.03 mg L-1) and winter (0.08 mg L-1 to 0.02 mg L-1). Significant decreases in SRP concentrations over annual (0.019 mg L-1 to 0.005 mg L-1), summer (0.018 mg L-1 to 0.004 mg L-1), autumn (0.019 mg L-1 to 0.005 mg L-1) and winter (0.033 mg L-1 to 0.005 mg L-1) periods were also reported. P concentrations following La-bentonite application varied across the lakes and were correlated positively with dissolved organic carbon concentrations. Relatively weak, but significant responses were reported for summer chlorophyll a concentrations and Secchi disk depths following La-bentonite applications, the 75th percentile values decreasing from 119 μg L-1 to 74 μg L-1 and increasing from 398 cm to 506 cm, respectively. Aquatic macrophyte species numbers and maximum colonisation depths increased following La-bentonite application from a median of 5.5 species to 7.0 species and a median of 1.8 m to 2.5 m, respectively. The aquatic macrophyte responses varied significantly between lakes. La-bentonite application resulted in a general improvement in water quality leading to an improvement in the aquatic macrophyte community within 24 months. However, because, the responses were highly site-specific, we stress the need for comprehensive pre- and post-application assessments of processes driving ecological structure and function in candidate lakes to inform future use of this and similar products. © 2015 The Authors.

Discover hidden collaborations