Project title: Linked laboratory and field investigations of engineered nanomaterial (ENM) behavior in selected soils and groundwaters
Researcher: Dr VIviana Bolanos
Nanotechnology, defined as the understanding and control of matter at dimensions between 1 and 100 nm, where unique phenomena enable novel applications (National Nanotechnology Initiative, 2009) is a rapid growth sector globally. Engineered nanomaterials (ENMs) are finding an ever increasing range of industrial applications, particularly in personal care products, medicines and in renewable energy technologies such as photovoltaics (PV). This growth is reflected in the rapidly increasing number of nanotechnology patents filed globally, up from 224 in 1991 to 12,776 in 2008 (Dang et al., 2010; Roco et al., 2011). In the United States alone, more than 6000 nanotechnology patents were issued in 2013, a 17% increase over the previous year (Jordan et al., 2012). ENMs fall into two broad categories; homogenous and heterogeneous. Homogeneous ENMs are typically metal or metal oxides, including silver, gold, zinc oxide and titanium oxide nanoparticles, having at least one dimension of <100 nm. Increasingly these engineered nanoparticles are also coated using a variety of materials to improve their performance for specific applications. Heterogeneous ENMs on the other hand include a wide variety of carbon-based nanoparticles (e.g. single or multi-walled carbon nanotubes (CNTs), graphene and fullerenes) that can employed as nano-carriers to encapsulate other materials (e.g. medicines) in drug-delivery systems. Carbon nanotubes are also employed in a range of engineering applications, including in the manufacture of photovoltaic (PV) solar panels, a rapidly growing market globally.
In this targeted project, we focus specifically on metal and metal oxide nanoparticles. Engineered titanium dioxide and zinc oxide nanoparticles are now very widely used in consumer products such as cosmetics, skin care products and sunscreens with high potential for dispersal into the environment, including into groundwater. Engineered silver nanoparticles (Ag-NP) are found in food packing, textiles, disinfectants, household appliances and in medicines. In recent years, Ag-NPs have been employed widely as biocide coatings on textile (clothing) surfaces, exploiting their powerful anti-microbial properties (Benn et al., 2010). Current global annual production of ENMs is estimated to be 5000 tonnes for TiO2 nanoparticles, 500 tonnes for Ag-NPs, and 350 tonnes for CNTs (Park et al., 2016). The ultimate â€˜end-of-lifeâ€™ fate of these particles in the environment remains highly uncertain, but current crude estimates, based on industry surveys in America, Europe, Asia and Australia suggest that approximately 20% of engineered nanoparticles may end up in soils (sensu-lato), 20% in surface and groundwater, a few percent in the atmosphere, with the balance ultimately entering landfills (Keller and Lazareva, 2013). As a result of their small size and high surface area to volume ratio they have the potential to be: (i) exceedingly mobile in porous geological media and (ii) geochemically reactive. It should be noted that ENMs can pass through 0.45ïm filters that are conventionally used to operationally define dissolved versus suspended materials, yet their geochemical and physio-chemical behaviour may differ substantially from that predicted by bare ions (e.g. Ag+, Ag2+) in solution (Park et al., 2016).