Fate and Transport of Nanomaterials in Aquatic Environments - Nanotechnologies for Water Environment Applications - page 545

The fate and transport of NMs and the related governing factors can be very
different in water, porous media and sediments. In general, the physical (particle size
and concentration, flow velocity, heterogeneity, collector grain size, etc.) and chemical
(pH, ion strength, particle surface chemistry, etc.) properties of the environment and the
evolution of surface characteristics of NMs (e.g., coatings, surface modifiers, etc.) are
always important. A NM in water is a special example of colloidal systems, where the
factors contributing most to the overall nature of the NMs' mobility are: (1) particle size,
(b) particle shape and flexibility, (c) surface (including electrical) properties, (d)
particle-particle interactions, and (e) particle-liquid (-solvent) interactions. In the water
environment, aggregation of NMs may be more important than deposition or attachment
of NMs onto suspended solids, living organisms or sediments. On the other hand, a NM
flow through porous media or sediments is another special example of colloidal systems,
where, not only the aforementioned five factors are important for both NMs and porous
media, transformation processes and interactions between the NM and the porous media
(filtration, adsorption/desorption, etc.) play important roles as well.
While this chapter is organized within the framework of existing information on
colloidal fate and transport, NMs do have some specific physical or chemical
interactions with their environment, which makes them substantially different from those
bulk materials of the same composition. Fig. 15.8 summarizes some important
interactions of NMs with the environment and living organisms.
It is possible that the unique characteristics of NMs result in harmful interactions
in the environment and biological systems. The cytotoxic mechanisms of NMs on living
organisms, particularly mammalian cells, depend on the fate and transport of NMs upon
their physical/chemical/biological interactions with cell materials. Oxidative stress,
metal toxicity and physical damage are the three proposed principal cytotoxic
mechanisms. Currently, there are many unknowns concerning fate and transport of NMs
in the environment, including effects of different interphase transfer and transformation
processes on the form, complexity, and the mechanisms of NM transport and removal in
the environment. In the future, intensive research (as shown in Table 15.1) is needed to
ensure safe manufacture and use of NMs.
15.7 References
Adamson, A.W. (1982). Physical Chemistry of Surfaces, 4 t h Ed., Wiley-Intersci., NY.
Alargova, R.G., Deguchi, S., and Tsujii, K. (2001). "Stable colloidal dispersions of
fullerenes in polar organic solvents."/. Am. Chem. Soc., 123, 10460-10467.
Andrievsky, G.V., Klochkov, V.K., Bordyuh, A., and Dovbeshko, G.I. (2002).
"Comparative analysis of two aqueous-colloidal solutions of Ceo fullerene with