Ottersberg, Germany
Ottersberg, Germany

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PubMed | Institute Dr Nowak, Natural England, Netherlands Institute of Ecology, Freshwater Research and 5 more.
Type: | Journal: Water research | Year: 2016

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: 1.4-6.7tonnesha(-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 0.08mgL(-1) in the 24 months pre-application to 0.03mgL(-1) in the 24 months post-application), particularly in autumn (0.08mgL(-1) to 0.03mgL(-1)) and winter (0.08mgL(-1) to 0.02mgL(-1)). Significant decreases in SRP concentrations over annual (0.019mgL(-1) to 0.005mgL(-1)), summer (0.018mgL(-1) to 0.004mgL(-1)), autumn (0.019mgL(-1) to 0.005mgL(-1)) and winter (0.033mgL(-1) to 0.005mgL(-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 119gL(-1) to 74gL(-1) and increasing from 398cm to 506cm, 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 1.8m to 2.5m, 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.


Crosa G.,University of Insubria | Yasseri S.,Institute Dr Nowak | Nowak K.-E.,Institute Dr Nowak | Canziani A.,Environmental Protection Councillorship of Varese District | And 2 more authors.
Fundamental and Applied Limnology | Year: 2013

Lake Varese is one of the first and most evident examples of cultural eutrophication in southern Europe (Northern Italy). Although internal actions (hypolimnetic water withdrawal and injection of pure oxygen) were implemented following the construction of a sewage collection system in 1986, the complete reversal of the lake's eutrophic condition has not yet been achieved. Since the internal P load in Lake Varese, estimated to be 5.6 t yr-1, is a determining factor in the continuation of the eutrophic status of the lake, in this study an application of a lanthanum-modified bentonite clay, able to bind phosphorus, was carried out in controlled enclosures for 12 months during 2009-2010. The results showed a sharp reduction (more than 80 %) of the P concentrations along the water column after the lanthanum-modified bentonite clay application and, from January onwards, the settled clay controlled the P release from the sediments, preventing a sharp increase in total P concentrations to values exceeding 0.28 mg P l-1 that took place from August until October in untreated conditions. Though this action proved to be efficient in controlling the P fluxes from the lake sediments, low levels of dissolved oxygen were maintained in the bottom layer of the lake. A delay in the reduction of the anoxia could be observed in longer than the temporal window used for the enclosure trial. The time required to attain a significant reduction in anoxic conditions during the thermal stratification period depends on the reduction of total P and on several additional factors. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung.


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.


Yasseri S.,Institute Dr Nowak | Epe T.S.,Institute Dr Nowak
Water Research | Year: 2015

In recent years, lanthanum modified bentonite has been increasingly applied to eutrophic lakes with the aim of converting potentially bio-available forms of phosphorus in sediments into biologically unavailable forms. In many of these applications, however, no attempts have been made to assess the efficiency and efficacy of the measure in terms of its effect on the sediment.In this study, we collected sediment cores from a heavily eutrophied lake that has previously been treated with lanthanum modified clay. This restoration method is based on the strong ionic bond formed between lanthanum and phosphate which results in the formation of LaPO4 (Rhabdophane) in the sediment.In order to determine the changes that had occurred in the sediments as a result of the addition of the clay, we measured the vertical distribution of lanthanum in the collected cores, calculated La:P ratios of the different sediment layers and used the ratios to determine whether or not the applied dosage was sufficient. By means of the geostatistical method of kriging these values were transferred into maps of different depth intervals to visualize the results.The results indicate that the La:P ratio may be a useful tool which allows lake managers to measure the vertical distribution of lanthanum in sediments following treatments and determine whether or not dosages are sufficient to permanently render sediment phosphorus biologically unavailable. The method may also provide a basis on which to decide whether or not smaller reapplications are needed and can be used to control the dispersion of the material. © 2015 Elsevier Ltd.


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.


In recent years, lanthanum modified bentonite has been increasingly applied to eutrophic lakes with the aim of converting potentially bio-available forms of phosphorus in sediments into biologically unavailable forms. In many of these applications, however, no attempts have been made to assess the efficiency and efficacy of the measure in terms of its effect on the sediment. In this study, we collected sediment cores from a heavily eutrophied lake that has previously been treated with lanthanum modified clay. This restoration method is based on the strong ionic bond formed between lanthanum and phosphate which results in the formation of LaPO4 (Rhabdophane) in the sediment. In order to determine the changes that had occurred in the sediments as a result of the addition of the clay, we measured the vertical distribution of lanthanum in the collected cores, calculated La:P ratios of the different sediment layers and used the ratios to determine whether or not the applied dosage was sufficient. By means of the geostatistical method of kriging these values were transferred into maps of different depth intervals to visualize the results. The results indicate that the La:P ratio may be a useful tool which allows lake managers to measure the vertical distribution of lanthanum in sediments following treatments and determine whether or not dosages are sufficient to permanently render sediment phosphorus biologically unavailable. The method may also provide a basis on which to decide whether or not smaller reapplications are needed and can be used to control the dispersion of the material.


PubMed | Institute Dr Nowak, CNR Water Research Institute, Lake Ecosystems Group, University of Southern Denmark and 5 more.
Type: | Journal: Water research | Year: 2016

This paper reviews the scientific knowledge on the use of a lanthanum modified bentonite (LMB) to manage eutrophication in surface water. The LMB has been applied in around 200 environments worldwide and it has undergone extensive testing at laboratory, mesocosm, and whole lake scales. The available data underline a high efficiency for phosphorus binding. This efficiency can be limited by the presence of humic substances and competing oxyanions. Lanthanum concentrations detected during a LMB application are generally below acute toxicological threshold of different organisms, except in low alkalinity waters. To date there are no indications for long-term negative effects on LMB treated ecosystems, but issues related to La accumulation, increase of suspended solids and drastic resources depletion still need to be explored, in particular for sediment dwelling organisms. Application of LMB in saline waters need a careful risk evaluation due to potential lanthanum release.

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