John P. Stegemeier^1,2 Benjamin P. Colman^1,3  Fabienne Schwab^1,4  and Gregory V. Lowry^1,2

The incorporation of engineered metal nanomaterials into consumer products leads to an increased demand to understand the environmental transformations and ultimate fate of these nanoparticles once released.  Although several studies have demonstrated nanoparticles are likely to transform in waste water treatment plants before being introduced into the environment, relatively few studies investigate the interactions between these transformed particles and the environment.  Sulfur interactions with soft metals such as silver are expected to dominate the potential environmental transformations.  This experiment spatially and temporally investigated the distribution and speciation of silver in the plant tissue harvested from hydroponically exposed plants by using a host of laboratory characterization techniques as well as synchrotron based X-ray absorption spectroscopic techniques.  Metal nanoparticles were found to be associated with the rhizodermis of the roots indicating limited transport into the roots and throughout the plant.  Silver sulfide nanoparticles were found to be taken into plants slower than their counterparts.  Metallic silver was identified in the samples exposed to Ag₂S NPs but the presence of metallic nanoparticles inside the plant tissue for all the samples may be expected as plants can spontaneously form metal nanoparticles as a response to high aqueous metal concentrations.

https://conf-slac.stanford.edu/ssrl-lcls-2013/sites/conf-slac.stanford.e...