Inhaltszusammenfassung

Over the last decade, the variety and number of products and techniques based on the use or the addition of engineered nanoparticles has increased dramatically. This includes among others the use of e. g. silver, titanium dioxide, or other nanoparticle in a multitude of personal care products, clothing, colours, and other consumer products (Schaumann et al., 2015), and their direct applica-tion in the environment, e. g., for site remediation (Fajardo et al., 201...Over the last decade, the variety and number of products and techniques based on the use or the addition of engineered nanoparticles has increased dramatically. This includes among others the use of e. g. silver, titanium dioxide, or other nanoparticle in a multitude of personal care products, clothing, colours, and other consumer products (Schaumann et al., 2015), and their direct applica-tion in the environment, e. g., for site remediation (Fajardo et al., 2015; Reichenauer et al., 2015) or drinking water treatment (Simeonidis et al., 2015). It is generally accepted that such nanoparticles can enter aquatic and terrestrial ecosystems and may impact biotic and abiotic processes in those environments. The environmental relevance was recognized longer than a decade ago, and in contrast to the situation for other innovative materials and compounds, the research on potential environmental impacts of engineered nanoparticles has actually started before ørst negative environmental eoeects were reported. The pioneer researchers were challenged by limited analytical access to the nanoparticles and demanding experiments aris-ing from the distinctive features of these emerging materials. Not only the chemical composition, but also speciøc particle characteristics determine their mobility, chemical aOEnity and biological eoeects. Even today, it is still highly challenging to detect nanoparticles in environmental matrices and distinguish them from an omnipresent natural colloidal background. The presentations and discussions on the International Workshop Nanoparticles in Soils and Waters: Fate, Transport and Eoeects, held 11th - 13th March, 2014 in Landau in der Pfalz, Germany, with 81 participants from 15 countries, 32 oral and 29 poster presentations (Schaumann, 2014), led to a common agreement that it is reasonable and required to summarize and critically discuss current approaches and re- search activities in a special issue on engineered nanoparticles in soils and waters. This special issue is a collection of 18 publications, part of which is based on presentations during the work-shop in Landau.. The publications cover a wide spectrum of relevant issues related to engineered nanoparticles in the environment: they (i) stand for the current state of knowledge, (ii) demonstrate actual approaches to experimentally investigate fate and biological eoeects of six representatives of engineered nanoparticles: Ag, AgCl, TiO2, zerovalent iron, magnetite and copper oxide and (iii) present new approaches for characterizing and modeling fate, eoeects and the life cycle of nanopar-ticles. As a large part of engineered nanoparticles enter the environment via wastewater, they will pass waste water treatment systems, which then serve as hotspots for their transformation determining the colloidal speciation and the chemical status of the nanoparticles released from the wastewater treatment plants. This is central for silver (Kaegi et al., 2015), but also for other oxidic and metallic nanoparticles (Schaumann et al., 2015). Also use activities for products containing engineered nanoparticles should be considered in exposure assessment. For example, the release of nanoma-terials from fabrics into the atmosphere is controlled by the activities performed when wearing these textiles (Wigger et al., 2015). When nanoparticles are released to the environment, they will undergo a multitude of additional colloidal and chemical transformation reactions. Aggregation and disaggregation of nanoparticles are only partly or slowly reversible (Metreveli et al., 2015). Thus, also the history of the nanoparticles is likely determining their properties and fuctioning. A general understanding of these coupled mechanisms is required to reliably predict fate and eoeect of nanoparticles using qualiøed, process-oriented models yet to be developed. Based on a comprehensive analysis of the current knowledge on the fate and eoeects of two promi-nent nanoparticles, namely silver and titanium dioxide, it became clear that the mechanism of sorp- tion of natural organic matter to the nanoparticles is central for the dynamics in colloidal states of the nanoparticles, but major controls for these interactions are still largely unknown (Schaumann et al., 2015). Recent approaches again underline the relevance of the interaction between organic matter, cations and nanoparticles (Loosli et al., 2015). For metallic nanoparticles, chemical trans- formations further complicate the process understanding. For example, it is consensus that silver nanoparticles undergo dissolution and oxidation with Ag2S as a thermodynamically determined endpoint. Also AgCl nanoparticles are transformed in to Ag2S (Kaegi et al., 2015). Although not fully understood, these processes aoeect the biological impact of nanoparticles (Farkas et al., 2015; Pradhan et al., 2015) and their colloidal stability and availability in biological test media (Nur et al., 2015). In natural systems, these processes will determine which organisms will be exposed to the nanoparticles and which toxicity mechanism applies (Schaumann et al., 2015). When used for site remediation, environmental conditions will control the eOEciency of the nanoparticles (Fajardo et al., 2015). Less is known about the fate and transport of nanoparticles in soils. The study by (Klitzke et al., 2015) demonstrates that natural organic matter can stabilize silver nanoparticles in soil solu-tion, at high nanoparticle concentration. This is in line with the observation that silver nanoparticles in saturated porous media can be mobile, but at lower Æow rates, higher ionic strength and in pres-ence of divalent cations transport is inhibited (Braun et al., 2015). For the transport of nanoparticles in soil under unsaturated transport conditions, the attachment of the nanoparticles to the air-water interface is highly relevant (Kumahor et al., 2015). These ønding should be considered in future research, as transport in soil often occurs under unsaturated conditions. A deeper understanding of the transformation mechanisms and the interplay between physico- chemical transformation, transport and biological impact requires the development and improve-ment of suitable analytical techniques (Schaumann et al., 2015). Meanwhile, a wide spectrum of nanoanalytical methods can be applied to investigate the current state of the nanoparticles. Sur-face enhanced Raman spectroscopy could help to characterize organic coatings of nanoparticles (K#hn et al., 2015), and advanced application of light scattering techniques may give further infor-mation on the structure and thickness of the organic coating (Tiraferri and Borkovec, 2015). Espe-cially the development of single particle analytics using inductively coupled plasma mass spec-trometry was a milestone regarding environmental nanoanalytics, but it is still a challenge to char-acterize and detect the nanoparticles in complex matrices (Schaumann et al., 2015). Ideally, risk assessment should allow prediction of transport, fate and biological eoeects of engi-neered nanoparticles on the basis of, ørst, a well deøned and known set of nanoparticle properties and, second, well deøned and known characteristics of the environmental system of interest. In their analysis of the suitability of recent fate models for exposure assessment, Koelmans et al. (2015) suggest applying a cost-eoeective multi-step approach from assessment on principles of read-across to higher tier assessments, for example on the basis of controlled model ecosystem øeld experiments. Fate models not only require knowledge on the fundamental transformation processes controlling the speciation of nanoparticles, but they also need to consider dynamics of environmental conditions and their spatial variability. A ørst approach for this is described by Sani- Kast et al. (2015) on the example of the Rh#ne River (France) using statistical approaches. The authors showed that the fate of engineered nanoparticles can be best predicted when aggregation is strong near the emission source. This might suggest that the tendency of nanoparticles to ag-gregate is the dominating property governing their transport and fate, but these two studies also demonstrate how important it is for modeling to understand the colloidal transformation processes and their dependence on the actual environmental conditions and their dynamics and variability.» weiterlesen» einklappen

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