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  • 1
    Language: English
    In: Water Research, January 2011, Vol.45(3), pp.1338-1346
    Description: The occurrence of the cyanobacterial toxins anatoxin-a (ATX) and cylindrospermopsin (CYN) in surface waters has been reported throughout the world. Beside degradation, sorption is an important pathway for toxin elimination if these resources are used for drinking water production via sediment passage. However, to date studies that systematically investigated sorption of these toxins onto sediments are lacking. Therefore, the aim of our work was (i) to determine the adsorption coefficients of ATX and CYN according to the Freundlich and Langmuir model for sediments of various textures and (ii) to derive sorption-relevant sediment characteristics. We determined sorption parameters in air-dried samples of eight differently textured sediments using batch experiments. Results for both toxins showed best fits with the Langmuir model. Organic C proved to be the main sediment parameter determining CYN sorption. There was no or little CYN sorption on sandy and silty sediments (0–39 μg kg ), respectively, presumably due to charge repulsion from the negatively charged surfaces. Sorption of ATX (max. sorbent loading ranging from 47 to 656 μg kg ) was much stronger than that of CYN (max. sorbent loading ranging from 0 to 361 μg kg ) and predominantly controlled by clay and to a minor degree also by organic C and silt. While ATX sorption to most sediments occurred mainly through cation exchange this mechanism played only a minor role in CYN sorption to organic C. Hence, high mobility for CYN and moderate mobility for ATX during sediment passage has to be expected.
    Keywords: OECD Guideline 106 ; Cation Bridging ; Cation Exchange ; Ionic Strength ; River Bank Filtration ; Cyanotoxin ; Subsurface Passage ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 2
    Language: English
    In: The Science of the Total Environment, Dec 1, 2015, Vol.535, p.54(7)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2014.10.108 Byline: Sondra Klitzke, George Metreveli, Andre Peters, Gabriele E. Schaumann, Friederike Lang Abstract: Nanoparticles enter soils through various pathways. In the soil, they undergo various interactions with the solution and the solid phase. We tested the following hypotheses using batch experiments: i) the colloidal stability of Ag NP increases through sorption of soil-borne dissolved organic matter (DOM) and thus inhibits aggregation; ii) the presence of DOM suppresses Ag oxidation; iii) the surface charge of Ag NP governs sorption onto soil particles. Citrate-stabilized and bare Ag NPs were equilibrated with (colloid-free) soil solution extracted from a floodplain soil for 24h. Nanoparticles were removed through centrifugation. Concentrations of free Ag ions and DOC, the specific UV absorbance at a wavelength of 254nm, and the absorption ratio [alpha].sub.254/[alpha].sub.410 were determined in the supernatant. Nanoparticle aggregation was studied using time-resolved dynamic light scattering (DLS) measurement following the addition of soil solution and 1.5mM Ca.sup.2+ solution. To study the effect of surface charge on the adsorption of Ag NP onto soil particles, bare and citrate-stabilized Ag NP, differing in the zeta potential, were equilibrated with silt at a solid-to-solution ratio of 1:10 and an initial Ag concentration range of 30 to 320[mu]g/L. Results showed that bare Ag NPs sorb organic matter, with short-chained organic matter being preferentially adsorbed over long-chained, aromatic organic matter. Stabilizing effects of organic matter only come into play at higher Ag NP concentrations. Soil solution inhibits the release of Ag.sup.+ ions, presumably due to organic matter coatings. Sorption to silt particles was very similar for the two particle types, suggesting that the surface charge does not control Ag NP sorption. Besides, sorption was much lower than in comparable studies with sand and glass surfaces. Article History: Received 29 September 2014; Revised 30 October 2014; Accepted 30 October 2014 Article Note: (miscellaneous) Editor: D. Barcelo
    Keywords: Nanoparticles ; Adsorption
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Science of the Total Environment, 15 June 2015, Vol.518-519, pp.130-138
    Description: Redox conditions are known to affect the fate of viruses in porous media. Several studies report the relevance of colloid-facilitated virus transport in the subsurface, but detailed studies on the effect of anoxic conditions on virus retention in natural sediments are still missing. Therefore, we investigated the fate of viruses in natural flood plain sediments with different sesquioxide contents under anoxic conditions by considering sorption to the solid phase, sorption to mobilized colloids, and inactivation in the aqueous phase. Batch experiments were conducted under oxic and anoxic conditions at pH values between 5.1 and 7.6, using bacteriophages MS2 and PhiX174 as model viruses. In addition to free and colloid-associated bacteriophages, dissolved and colloidal concentrations of Fe, Al and organic C as well as dissolved Ca were determined. Results showed that regardless of redox conditions, bacteriophages did not adsorb to mobilized colloids, even under favourable charge conditions. Under anoxic conditions, attenuation of bacteriophages was dominated by sorption over inactivation, with MS2 showing a higher degree of sorption than PhiX174. Inactivation in water was low under anoxic conditions for both bacteriophages with about one log decrease in concentration during 16 h. Increased Fe/Al concentrations and a low organic carbon content of the sediment led to enhanced bacteriophage removal under anoxic conditions. However, even in the presence of sufficient Fe/A-(hydr)oxides on the solid phase, bacteriophage sorption was low. We presume that organic matter may limit the potential retention of sesquioxides in anoxic sediments and should thus be considered for the risk assessment of virus breakthrough in the subsurface.
    Keywords: Colloid Mobilization ; Phage ; Riverbank Filtration ; Sesquioxide ; Virus ; Zeta Potential ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 4
    Language: English
    In: Water Research, 01 April 2012, Vol.46(5), pp.1549-1555
    Description: One possible consequence of increasing water temperatures due to global warming in middle Europe is the proliferation of cylindrospermopsin-producing species from warmer regions. This may lead to more frequent and increased cylindrospermopsin (CYN) concentrations in surface waters. Hence, efficient elimination of CYN is important where contaminated surface waters are used as a resource for drinking water production via sediment passage. Sediments are often characterized by a lack of oxygen and low temperature (i.e. approx. 10 °C). The presence of dissolved organic carbon (DOC) is not only known to enhance but also to retard contaminant degradation by influencing the extent of lag phases. So far CYN degradation has only been investigated under oxic conditions and at room temperature. Therefore, the aim of our experiments was to understand CYN degradation, focusing on the effects of i) anoxic conditions, ii) low temperature (i.e. 10 °C) in comparison to room temperature (23 ± 4 °C) and iii) DOC on lag phases. We used two natural sandy sediments (virgin and preconditioned) and surface water to conduct closed-loop column experiments. Anoxic conditions either inhibited CYN degradation completely or retarded CYN breakdown in comparison to oxic conditions ( (oxic) = 2.4 days, (anoxic) = 23.6 days). A decrease in temperature from 20 °C to 10 °C slowed down degradation rates by a factor of 10. The presence of DOC shortened lag phases in virgin sediments at room temperature but induced a lag phase in preconditioned sediments at 10 °C, indicating potential substrate competition. These results show that information on physico-chemical conditions in sediments is crucial to assess the risk of CYN breakthrough. ► A temperature decrease from 20 °C to 10 °C slows down CYN degradation by a factor of 10. ► CYN degradation in sediments is retarded or inhibited under anoxic conditions. ► DOC may both shorten and induce lag phases. ► At 10 °C, DOC has no effect on CYN degradation rate.
    Keywords: Riverbank Filtration ; Artificial Groundwater Recharge ; Sand Filtration ; Cyanobacterial Toxin ; Sediment Preconditioning ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 5
    Language: English
    In: Environmental Pollution, March, 2014, Vol.186, p.7(7)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.envpol.2013.11.011 Byline: Lena Vierke, Axel Moller, Sondra Klitzke Abstract: The aim of this study was to gain an understanding of the transport of C.sub.4-10 perfluoroalkyl carboxylic acids (PFCAs) and C.sub.4,6,8 perfluoroalkyl sulfonic acids (PFSAs) in a water-saturated sediment column representing a riverbank filtration scenario under near-natural conditions. Short-chain PFCAs and PFSAs with up to six C-atoms showed complete tracer-like breakthrough. Longer chain ones were retarded due to sorption to the sediment or due to other processes in the aqueous phase. The study reports the first column derived sediment-water partition coefficients ranging from 0.01 cm.sup.3 g.sup.-1 to 0.41 cm.sup.3 g.sup.-1 for C.sub.4,6 PFSAs and from 0.0 cm.sup.3 g.sup.-1 to 6.5 cm.sup.3 g.sup.-1 for C.sub.4,5,6,8,9 PFCAs. The results clearly indicate that short-chain PFCAs and PFSAs may pose a problem if contaminated surface waters are used for drinking water production via riverbank filtration. Author Affiliation: (a) Federal Environment Agency, Worlitzer Platz 1, 06844 Dessau-Ro[sz]lau, Germany (b) Leuphana University of Luneburg, Scharnhorststr. 1, 21335 Luneburg, Germany (c) Helmholtz-Zentrum Geesthacht, Max-Planck Str. 1, 21502 Geesthacht, Germany (d) Federal Environment Agency, Schichauweg 58, 12307 Berlin, Germany Article History: Received 23 May 2013; Revised 14 October 2013; Accepted 15 November 2013
    Keywords: Sulfonic Acids -- Investigations ; Water -- Investigations ; Tracers (Biology) -- Investigations ; Sediments (Geology) -- Investigations
    ISSN: 0269-7491
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: The Science of the Total Environment, Dec 1, 2015, Vol.535, p.122(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2014.12.026 Byline: Melanie Kuhn, Natalia P. Ivleva, Sondra Klitzke, Reinhard Niessner, Thomas Baumann Abstract: The widespread use of engineered inorganic nanoparticles (EINP) leads to a growing risk for an unintended release into the environment. Despite the good characterization of EINP in regard to their function scale and the application areas, there is still a gap of knowledge concerning their behaviour in the different environmental compartments. Due to their high surface to volume ratio, surface properties and existence or development of a coating are of high importance for their stability and transport behaviour. However, analytical methods to investigate organic coatings on nanoparticles in aqueous media are scarce. We used Raman microspectroscopy in combination with surface-enhanced Raman scattering (SERS) to investigate humic acid coatings on silver nanoparticles under environmentally relevant conditions and in real world samples. This setup is more challenging than previous mechanistic studies using SERS to characterize the humic acids in tailored settings where only one type of organic matter is present and the concentrations of the nanoparticles can be easily adjusted to the experimental needs. SERS offers the unique opportunity to work with little sample preparation directly with liquid samples, thus significantly reducing artefacts. SERS spectra of different natural organic matter brought into contact with silver nanoparticles indicate humic acid in close proximity to the nanoparticles. This coating was also present after several washing steps by centrifugation and resuspension in deionized water and after an increase in ionic strength. Article History: Received 15 October 2014; Revised 5 December 2014; Accepted 5 December 2014
    Keywords: Nanoparticles – Investigations ; Coatings – Investigations ; Humic Acids – Investigations
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 7
    Language: English
    In: Science of the Total Environment, 15 December 2018, Vol.645, pp.1153-1158
    Description: Engineered nanomaterials (ENM) such as nano-sized cerium dioxide (CeO ) are increasingly applied. Meanwhile, concerns on their environmental fate are rising. Understanding the fate of ENM within and between environmental compartments such as surface water and groundwater is crucial for the protection of drinking water resources. Therefore, the colloidal stability of CeO ENM (2 mg L ) was assessed with various surface coatings featuring different physico-chemical properties such as weakly anionic polyvinyl alcohol (PVA), strongly anionic polyacrylic acid (PAA) or complex natural organic matter (NOM) at various water compositions in batch experiments (pH 2–12, ionic strength 0–5 mM KCl or CaCl ). While uncoated CeO ENM aggregate in the range of pH 4–8 in 1 mM KCl solution, the results show that PAA, PVA and NOM surface coatings stabilize CeO -ENM at neutral and alkaline pH in 1 mM KCl solution. Stabilization by PAA and NOM is associated with strongly negative zeta potentials below −20 mV, suggesting electrostatic repulsion as stabilization mechanism. No aggregation was detected up to 5 mM KCl for PAA- and NOM-coated CeO ENM. In contrast, CaCl induced aggregation at 〉2.2 mM CaCl for PAA and NOM-coated CeO ENM respectively. PVA-coated ENM showed zeta potentials of −15 mV to −5 mV in the presence of 0–5 mM ionic strength, suggesting steric effects as stabilization mechanism. The hydrodynamic diameter of PVA-coated ENM was larger compared to PAA and NOM at low ionic strength, but the size did not increase with ionic strength of the suspensions. The effect of ionic strength and counter ion valency (pH 7) on the colloidal stability of ENM depends on the prevailing stabilization mechanism of the organic coating. NOM can be similarly effective in colloidal stabilization of CeO -ENM as PAA. Our results suggest natural Ca-rich waters will lead to ENM agglomeration even of coated CeO -ENM.
    Keywords: Ceo2-Enm ; Nanomaterial Functionalization ; Suspension Stability ; Zeta Potential ; Cation Valency ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 8
    Language: English
    In: Environmental Pollution, March 2014, Vol.186, pp.7-13
    Description: The aim of this study was to gain an understanding of the transport of C perfluoroalkyl carboxylic acids (PFCAs) and C perfluoroalkyl sulfonic acids (PFSAs) in a water-saturated sediment column representing a riverbank filtration scenario under near-natural conditions. Short-chain PFCAs and PFSAs with up to six C-atoms showed complete tracer-like breakthrough. Longer chain ones were retarded due to sorption to the sediment or due to other processes in the aqueous phase. The study reports the first column derived sediment–water partition coefficients ranging from 0.01 cm  g to 0.41 cm  g for C PFSAs and from 0.0 cm  g to 6.5 cm  g for C PFCAs. The results clearly indicate that short-chain PFCAs and PFSAs may pose a problem if contaminated surface waters are used for drinking water production via riverbank filtration. Quantification of breakthrough of perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) under conditions simulating a riverbank filtration scenario.
    Keywords: Riverbank Filtration ; Pfoa ; Pfcas ; Pfsas ; Sediment–Water Partition Coefficient ; Column Study ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
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  • 9
    Language: English
    In: Science of the Total Environment, 01 December 2015, Vol.535, pp.54-60
    Description: Nanoparticles enter soils through various pathways. In the soil, they undergo various interactions with the solution and the solid phase. We tested the following hypotheses using batch experiments: i) the colloidal stability of Ag NP increases through sorption of soil-borne dissolved organic matter (DOM) and thus inhibits aggregation; ii) the presence of DOM suppresses Ag oxidation; iii) the surface charge of Ag NP governs sorption onto soil particles. Citrate-stabilized and bare Ag NPs were equilibrated with (colloid-free) soil solution extracted from a floodplain soil for 24 h. Nanoparticles were removed through centrifugation. Concentrations of free Ag ions and DOC, the specific UV absorbance at a wavelength of 254 nm, and the absorption ratio α /α were determined in the supernatant. Nanoparticle aggregation was studied using time-resolved dynamic light scattering (DLS) measurement following the addition of soil solution and 1.5 mM Ca solution. To study the effect of surface charge on the adsorption of Ag NP onto soil particles, bare and citrate-stabilized Ag NP, differing in the zeta potential, were equilibrated with silt at a solid-to-solution ratio of 1:10 and an initial Ag concentration range of 30 to 320 μg/L. Results showed that bare Ag NPs sorb organic matter, with short-chained organic matter being preferentially adsorbed over long-chained, aromatic organic matter. Stabilizing effects of organic matter only come into play at higher Ag NP concentrations. Soil solution inhibits the release of Ag ions, presumably due to organic matter coatings. Sorption to silt particles was very similar for the two particle types, suggesting that the surface charge does not control Ag NP sorption. Besides, sorption was much lower than in comparable studies with sand and glass surfaces.
    Keywords: Isoelectric Point ; Cation Valency ; Initial Nanoparticle Concentration ; Exchangeability of Sorbed Ag Ions ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 10
    Language: English
    In: Science of the Total Environment, 01 December 2015, Vol.535, pp.122-130
    Description: The widespread use of engineered inorganic nanoparticles (EINP) leads to a growing risk for an unintended release into the environment. Despite the good characterization of EINP in regard to their function scale and the application areas, there is still a gap of knowledge concerning their behaviour in the different environmental compartments. Due to their high surface to volume ratio, surface properties and existence or development of a coating are of high importance for their stability and transport behaviour. However, analytical methods to investigate organic coatings on nanoparticles in aqueous media are scarce. We used Raman microspectroscopy in combination with surface-enhanced Raman scattering (SERS) to investigate humic acid coatings on silver nanoparticles under environmentally relevant conditions and in real world samples. This setup is more challenging than previous mechanistic studies using SERS to characterize the humic acids in tailored settings where only one type of organic matter is present and the concentrations of the nanoparticles can be easily adjusted to the experimental needs. SERS offers the unique opportunity to work with little sample preparation directly with liquid samples, thus significantly reducing artefacts. SERS spectra of different natural organic matter brought into contact with silver nanoparticles indicate humic acid in close proximity to the nanoparticles. This coating was also present after several washing steps by centrifugation and resuspension in deionized water and after an increase in ionic strength.
    Keywords: Engineered Inorganic Nanoparticles ; Coatings ; Natural Organic Matter ; Surface-Enhanced Raman Scattering ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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