Over the past three years the UC Center for Environmental Implications of Nanotechnology (UC CEIN) has been studying the toxicity and fate and transport of several important commercial nanoparticles, including metal and metal oxides, and carbon nanotubes. There are some emerging patterns with regards to nanoparticle stability in natural media, rates of sedimentation, efficiency of attachment of the nanoparticles to sand and clays, dissolution patterns and photoactivity. Of critical importance is an understanding of the composition of the aqueous matrix in which the nanoparticles are suspended, particularly with regards to the concentration of organic materials, ionic strength, and the nature of the cations present. The nanoparticles are likely to remain suspended if there are more than a few mg/L of organic material, particularly at low ionic strength. Hard water (i.e., with high [Ca2+] and/or other divalent cations) can quickly change the balance of the interactions among nanoparticles and between nanoparticles and the porous medium in which they are being transported. Coatings and organic capping agents on the surface of the nanoparticle can significantly increase the mobility of the nanoparticles in the environment. Understanding of the role of these various water constituents can be used to design either more effective injection of nanomaterials (e.g., nano-zerovalent iron) into the subsurface, or arrest their transport if they are unexpectedly mobile in groundwater.

Emerging trends in nanoparticle fate and transport

244th National Meeting (2012)

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