Person: Klitzke, Sondra
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Veröffentlichung Retention and remobilization mechanisms of environmentally aged silver nanoparticles in an artificial riverbank filtration system(2018) Metreveli, George; Degenkolb, Laura; Philippe, Allan; Klitzke, Sondra; Brandt, Anja; Zehlike, LisaVeröffentlichung Aggregation of TiO2 and Ag nanoparticles in soil solution - Effects of primary nanoparticle size and dissolved organic matter characteristics(2019) Degenkolb, Laura; Peters, André; Ellerbrock, Ruth H.; Klitzke, Sondra; Zehlike, LisaThe colloidal stability of nanoparticles NP in soil solution is important to assess their potential effects on ecosystems. The aim of this work was to elucidate the interactions between initial particle size di, particle number concentration (N0) as well as the characteristics of dissolved organic matter (DOM) for stabilizing Ag NP and TiO2 NP. In batch experiments using time-resolved dynamic light scattering (DLS), we investigated the aggregation of TiO2 NP (79 nm, 164 nm) and citrate-stabilised Ag NP (73 nm, 180 nm) in Ca2+ solution (2 mM) and two soil solutions, one extracted from a farmland and one from a floodplain soil (each containing 2 mM Ca2+). Our results demonstrate that the initial particle size and the particle number concentration affected aggregation more strongly in the presence of DOM than without DOM. The composition of DOM also affected aggregate size: NP formed larger aggregates in the presence of hydrophilic DOM than in the presence of hydrophobic DOM. Hydrophilic DOM showed a larger charge density than hydrophobic DOM. If Ca2+ is present, it may bridge DOM molecules, which may lead to greater NP destabilization. The results demonstrate that DOM interaction with NP may not only vary for different DOM characteristics (i.e. charge density) but may also be influenced by the presence of multivalent cations and different NP material; thus the effect of DOM on NP colloidal stability is not uniform. © 2019 The Authors. Published by Elsevier B.V.Veröffentlichung Transport and retention of differently coated CeO2 nanoparticles in saturated sediment columns under laboratory and near-natural conditions(2019) Degenkolb, Laura; Dippon-Deissler, Urs; Klitzke, Sondra; Pabst, SilkeWhere surface-functionalized engineered nanoparticles (NP) occur in drinking water catchments, understanding their transport within and between environmental compartments such as surface water and groundwater is crucial for risk assessment of drinking water resources. The transport of NP is mainly controlled by (i) their surface properties, (ii) water chemistry, and (iii) surface properties of the stationary phase. Therefore, functionalization of NP surfaces by organic coatings may change their fate in the environment. In laboratory columns, we compared the mobility of CeO2 NP coated by the synthetic polymer polyacrylic acid (PAA) with CeO2 NP coated by natural organic matter (NOM) and humic acid (HA), respectively. The effect of ionic strength on transport in sand columns was investigated using deionized (DI) water and natural surface water with 2.2 mM Ca2+ (soft) and 4.5 mM Ca2+ (hard), respectively. Furthermore, the relevance of these findings was validated in a near-natural bank filtration experiment using HA-CeO2 NP. PAA-CeO2 NP were mobile under all tested water conditions, showing a breakthrough of 60% irrespective of the Ca2+ concentration. In contrast, NOM-CeO2 NP showed a lower mobility with a breakthrough of 27% in DI and < 10% in soft surface water. In hard surface water, NOM-CeO2 NP were completely retained in the first 2 cm of the column. The transport of HA-CeO2 NP in laboratory columns in soft surface water was lower compared to NOM-CeO2 NP with a strong accumulation of CeO2 NP in the first few centimeters of the column. Natural coatings were generally less stabilizing and more susceptible to increasing Ca2+ concentrations than the synthetic coating. The outdoor column experiment confirmed the low mobility of HA-CeO2 NP under more complex environmental conditions. From our experiments, we conclude that the synthetic polymer is more efficient in facilitating NP transport than natural coatings and hence, CeO2 NP mobility may vary significantly depending on the surface coating. © The Author(s) 2019Veröffentlichung The fate of silver nanoparticles in riverbank filtration systems - The role of biological components and flow velocity(2020) Degenkolb, Laura; Leuther, Frederic; Klitzke, Sondra; Lüderwald, SimonRiverbank filtration is a natural process that may ensure the cleaning of surface water for producing drinking water. For silver nanoparticles (AgNP), physico-chemical interaction with sediment surfaces is one major retention mechanism. However, the effect of flow velocity and the importance of biological retention, such as AgNP attachment to biomass, are not well understood, yet. We investigated AgNP (c=0.6 mg L-1) transport at different spatial and temporal scales in pristine and previously pond water-aged sediment columns. Transport of AgNP under near-natural conditions was studied in a long-term riverbank filtration experiment over the course of one month with changing flow scenarios (i.e. transport at 0.7m d-1, stagnation, and remobilization at 1.7m d-1). To elucidate retention processes, we conducted small-scale lab column experiments at low (0.2m d-1) and high (0.7m d-1) flow rate using pristine and aged sediments. Overall, AgNP accumulated in the upper centimeters of the sediment both in lab and outdoor experiments. In the lab study, retention of AgNP by attachment to biological components was very effective under high and low flow rate with nearly complete NP accumulation in the upper 2mm. When organic material was absent, abiotic filtration mechanisms led to NP retention in the upper 5 to 7cm of the column. In the long-term study, AgNP were transported up to a depth of 25cm. For the pristine sediment in the lab study and the outdoor experiments only erratic particle breakthrough was detected in a depth of 15cm. We conclude that physico-chemical interactions of AgNP with sediment surfaces are efficient in retaining AgNP. The presence of organic material provides additional retention sites which increase the filtration capacity of the system. Nevertheless, erratic breakthrough events might transport NP into deeper sediment layers. © 2019 The Authors. Published by Elsevier B.V.Veröffentlichung The variable fate of Ag and TiO2 nanoparticles in natural soil solutions - sorption of organic matter and nanoparticle stability(2019) Degenkolb, Laura; Kaupenjohann, Martin; Klitzke, SondraEngineered nanoparticles (NP) like Ag and TiO2 offer unique properties for various applications. Thus, the entry of the NP in soil environments is expected to increase in the future due to their growing industrial use. To avoid potential hazards due to these anthropogenic products, NP behavior in the environment should be well understood. In natural soil solutions, we investigated NOM adsorption onto Ag and TiO2 NP and its influence on NP colloidal stability. Therefore, we extracted soil solutions from a floodplain soil (Fluvisol) and a farmland soil (Cambisol) differing in NOM quality and inorganic ion concentration. We measured the amount of adsorbed organic carbon as well as changes in aromaticity and molecular weight of NOM upon adsorption onto NP. Additionally, the size and zeta potential of NP in both soil solutions were investigated. We observed that the highly hydrophilic NOM of floodplain soil solution rich in inorganic ions strongly adsorbed to Ag but not to TiO2 NP. Instead, sorption to TiO2 NP was observed for the more hydrophobic NOM of the farmland soil with low ionic strength which did not sorb to Ag NP. These differences had a strong effect on NP stability, leading to Ag NP destabilization in case of floodplain soil solution and TiO2 NP stabilization in the presence of farmland soil solution. Our results point out the necessity of studies in more complex systems and suppose that oxic and metallic NP might show very different fate depending on the environment they are exposed to. © Springer Nature Switzerland AG 2019