Overall findings from the project Nanomobil (2014 – 2017)
The objective of the Nanomobil project was to study the interaction between synthetic silver nanoparticles (Ag-NP) and the biosphere, pedosphere, and hydrosphere under realistic conditions. The focus of this project was on the future hazard and risk assessment of nanoparticles in the environment. Another aim of the Nanomobil project was to investigate the effects of nanoparticles on organisms and associated effects on the environment.
RWTH Aachen University, Chair of Environmental Biology and Chemodynamics
Acute and chronic effects of silver nanoparticles and silver nitrate on various terrestrial and aquatic organisms have been investigated. As expected, silver nitrate induced a higher mortality in earthworms than silver nanoparticles. Here, species-dependent sensitivities were observed: Lumbricus terrestris was more sensitive than Eisenia fetida. Springtails, Folsomia candida, showed chronic effects in the form of reduced reproduction for two differently stabilized silver nanoparticles at similar concentrations (surfactant- and polymer-stabilized silver nanoparticles were investigated). The collembolan species also proved to be the most sensitive terrestrial organism. The aquatic organism Gammarus pulex showed significant effects on feeding behaviour even at low concentrations (3 µg Ag/L).
In addition to ecotoxicological effects, the influence of earthworms on the mobility of two different silver nanoparticles in natural soil was investigated. The dwelling activity of earthworms contributed to a slightly increased leaching of some of the nanomaterials in the soil; however, the excrements of the worms also increasingly retained silver nanoparticles in the upper part of the soil. It could also be shown that the coating of the nanoparticles influenced the transport behaviour of the silver nanoparticles. However, overall, the transport of silver nanoparticles in the soil is very limited and most of the applied material remains in the uppermost soil layer.
RWTH Aachen University, Chair of Engineering Geology and Hydrogeology
Within the subproject Hydrosphere, the transport and the long-term behaviour of surfactant-stabilized and polymer-stabilized synthetic silver nanoparticles in aquifer material were investigated. Silicate-dominated and carbonate-dominated aquifer materials were considered due to their importance in drinking water supply. In the project, column experiments on the laboratory scale were carried out.
In the silicate-dominated aquifer material, the influence of hydraulic and physico-chemical factors on the transport and long-term behaviour of Silver nanoparticles was investigated. The main influencing factors for the transport were the content of fine aquifer sediment (with particles < 0.063 mm), the intervals between irrigations, the ionic strength and the composition of the background solution as well as the method of stabilizing the nanoparticles. In addition, studies on the transport of polymer-stabilized silver nanoparticles in the presence of phosphorus were performed in the silicate-dominated aquifer material. Silver nanoparticle transport depends on the presence or absence of soil organic matter (SOM) as well as on the type of phosphorus species (organic or inorganic). The pH value and the grain size also play a significant role in leaching of the silver nanoparticles. In the carbonate-dominated porous material (natural aquifer material and artificial quartz-calcium carbonate mixture with changing carbonate content) the influence of the carbonate content, the stabilization method of silver nanoparticles and SOM on the transport was investigated. In some cases, considerable differences were found in the retention behaviour of surfactant- and polymer-stabilized silver nanoparticles.
gaiac – Research Institute for Ecosystem Analysis and Evaluation e.V.
Within the framework of the Nanomobil project, long-term effects of silver nanoparticles on a natural biocoenosis of soil organisms were investigated. The study was carried out in so-called terrestrial model ecosystems (TME) under field conditions over a period of one-year comparing silver nanoparticles stabilized with surfactants and polymers as well as silver nitrate. Various soil organisms showed a significant increase in activity (escape behaviour from the soil) in the short term (after 14 d). After 6 months, some species of the collembolans and of the horn mites as well as the associated juveniles were significantly reduced compared to the control. The sensitivity of the collembolans to the two silver nanoparticles’ species was different and some of them reacted more sensitively to the Silver nanoparticles than to silver nitrate. The community of earthworms could only be studied after one year and was not affected by Silver nanoparticles one year after application.
Research Centre Juelich – Institute for Biosciences and Earth Sciences
Within the framework of the Nanomobil subproject “Pedosphere”, investigations were carried out on surface-stabilized silver nanoparticles in soil under the influence of environmentally relevant weather conditions such as drought periods and rain events. Transport and deposition results from laboratory column experiments and on a larger scale from lysimetric studies showed that dry periods led to a complete decrease of silver nanoparticle mobility. In addition, for all rain events, the breakthrough of silver nanoparticles was very small and almost all silver nanoparticles remained in the upper soil horizon. However, heavy rain events and natural rain conditions showed a displacement of silver nanoparticles within the Ap horizon (in the layer of typical soil tillage).
Postnova Analytics GmbH
Postnova Analytics GmbH developed methods for the characterization of silver nanoparticles in complex environmental matrices down to trace concentrations. Asymmetric flux-field-flow fractionation (AF4) was used. By enrichment of the silver nanoparticles, directly in the AF4 separation channel, application of the “slot-outlet function” for removal of the silver nanoparticle-free eluent stream as well as the coupling with the strong inductive-coupled plasma mass spectrometry (ICP-MS), detection limits for the silver nanoparticle determination in liquid samples in the sub-µg/L (ppb) range could be realized. The AF4-ICP-MS coupling was finally used to investigate the transport behaviour of silver nanoparticles in soils
Grant – No.: 03X0151
Duration : 01.08.2014-31.07.2017 (extended to 31.10.2017)
Prof. Dr. Rafig Azzam, Department of Engineering Geology and Hydrogeology (LIH), RWTH Aachen
Department of Engineering Geology and Hydrogeology (LIH),
RWTH Aachen, Aachen (DE)
Research institute for ecosystem analysis and assessment (gaiac),
RWTH Aachen, Aachen (DE)