Modeling the flows of engineered nanomaterials during waste handling.

Little is known about the behavior of engineered nanomaterials (ENM) at the interface from the technosphere to the ecosphere. Previous modeling of ENM flows to the environment revealed that significant amounts of ENM enter the waste stream and therefore waste incineration plants and landfills. It is the aim of this study to model the flows of ENM during waste incineration and landfilling in greater depth by including a more detailed description of the different processes and considering ENM-specific transformation reactions. Four substances were modeled: nano-TiO2, nano-ZnO, nano-Ag and carbon nanotube (CNT). These ENM are representative for commonly used materials and products, illustrating a variety of ENM with different behavior. The modeling was performed for Switzerland where almost 100% of the municipal waste and sewage sludge are burned. The mass-based modeling showed that ­ despite several differences among the models for nano-TiO2, nano-ZnO and nano-Ag (e.g. partial dissolution of nano-ZnO in acid washing of exhaust air or fly ash) ­ the major ENM flows go from the waste incineration plant to the landfill as bottom ash. All other flows within the system boundary (e.g. with the fly ash) were predicted to be about one magnitude smaller than the bottom ash flow. A different ENM distribution was found for CNTs that are expected to burn to a large extent (94%) so that only insignificant amounts remain in the system. The results of the modeling show that waste incineration can have a strong influence on some ENM but that still the majority of the ENM-mass is expected to end up in landfills.

Application of nanoscale zero valent iron (NZVI) for groundwater remediation in Europe.

PURPOSE: Nanoscale zero valent iron (NZVI) is emerging as a new option for the treatment of contaminated soil and groundwater targeting mainly chlorinated organic contaminants (e.g., solvents, pesticides) and inorganic anions or metals. The purpose of this article is to give a short overview of the practical experience with NZVI applications in Europe and to present a comparison to the situation in the USA. Furthermore, the reasons for the difference in technology use are discussed. METHOD: The results in this article are based on an extensive literature review and structured discussions in an expert workshop with experts from Europe and the USA. The evaluation of the experiences was based on a SWOT (strength, weakness, opportunity, threat) analysis. RESULT: There are significant differences in the extent and type of technology used between NZVI applications in Europe and the USA. In Europe, only three full-scale remediations with NZVI have been carried out so far, while NZVI is an established treatment method in the USA. Bimetallic particles and emulsified NZVI, which are extensively used in the USA, have not yet been applied in Europe. Economic constraints and the precautionary attitude in Europe raise questions regarding whether NZVI is a cost-effective method for aquifer remediation. Challenges to the commercialization of NZVI include mainly non-technical aspects such as the possibility of a public backlash, the fact that the technology is largely unknown to consultants, governments and site owners as well as the lack of long-term experiences. CONCLUSION: Despite these concerns, the results of the current field applications with respect to contaminant reduction are promising, and no major adverse impacts on the environment have been reported so far. It is thus expected that these trials will contribute to promoting the technology in Europe.

Nanofiltration and nanostructured membranes--should they be considered nanotechnology or not?

Nanofiltration is frequently associated with nanotechnology - obviously because of its name. However, the term "nano" in nanofiltration refers - according to the definition of the International Union of Pure and Applied Chemistry (IUPAC) - to the size of the particles rejected and not to a nanostructure as defined by the International Organisation of Standardisation (ISO) in the membrane. Evidently, the approach to standardisation of materials differs significantly between membrane technology and nanotechnology which leads to considerable confusion and inconsistent use of the terminology. There are membranes that can be unambiguously attributed to both membrane technology and nanotechnology such as those that are functionalized with nanoparticles, while the classification of hitherto considered to be conventional membranes as nanostructured material is questionable. A driving force behind the efforts to define nanomaterials is not least the urgent need for the regulation of the use of nanomaterials. Since risk estimation is the basis for nanotechnology legislation, the risk associated with nanomaterials should also be reflected in the underlying standards and definitions. This paper discusses the impacts of the recent attempts to define nanomaterials on membrane terminology in the light of risk estimations and the need for regulation.

Exposure modeling of engineered nanoparticles in the environment.

The aim of this study was to use a life-cycle perspective to model the quantities of engineered nanoparticles released into the environment. Three types of nanoparticles were studied: nano silver (nano-Ag), nano TiO2 (nano-TiO2), and carbon nanotubes (CNT). The quantification was based on a substance flow analysis from products to air, soil, and water in Switzerland. The following parameters were used as model inputs: estimated worldwide production volume, allocation of the production volume to product categories, particle release from products, and flow coefficients within the environmental compartments. The predicted environmental concentrations (PEC) were then compared to the predicted no effect concentrations (PNEC) derived from the literature to estimate a possible risk. The expected concentrations of the three nanoparticles in the different environmental compartments vary widely, caused by the different life cycles of the nanoparticle-containing products. The PEC values for nano-TiO2 in water are 0.7--16 microg/L and close to or higher than the PNEC value for nano-TiO2 (< 1 microg/L). The risk quotients (PEC/PNEC) for CNT and nano-Ag were much smaller than one, therefore comprising no reason to expect adverse effects from those particles. The results of this study make it possible for the first time to carry out a quantitative risk assessment of nanoparticles in the environment and suggest further detailed studies of nano-TiO2.