Student conducts internationally collaborative research

John Stegemeier (left) and Clement Levard (right) in the lab.

John Stegemeier and Clement Levard at the CEREGE in France.

John Stegemeier, a 3rd year PhD student at Carnegie Mellon University, conducted research with CEINT collaborators from CEREGE (Centre de Recherche et d’Enseignement de Géosciences de l’Environnement) near Aix-en-Provence, France in February 2014. This trip was made possible with funding from an NSF IGERT traineeship at Carnegie Mellon.

John's research focuses on the uptake of nanoparticles into plants and the effect of environmental transformations that can modify the properties of the nanoparticles. Specifically, he investigated the phytoabsorption of pristine silver (Ag0) and transformed silver sulfide (Ag2S) nanoparticles into Egeria densa plants. This experiment was conducted through the CEINT Adopt-A-Box mesocosm program, in which researchers from several CEINT institutions assess the impact of nanoparticles in simulated wetland environments at Duke University.

During his visit to France and with the help of Clement Levard and Nathan Bossa at CEREGE, John imaged different sections of the E. densa plants (leaves, stems and whole plant) from the mesocosms exposed to Ag2S and Ag0 nanoparticles using X-ray tomography. X-ray computed tomography (CT) uses a series of two dimensional X-ray images collected at hundreds of angles to construct a 3D rendering to identify the distribution of silver nanoparticles in the plant tissue as relatively more dense regions. The E. densa samples were also spatially analyzed for total metals using laser ablation-ICP-MS to confirm that the dense regions identified by the CT are silver.

This research produces scientifically valuable and environmentally realistic knowledge on the uptake of nanoparticles by plants. It also encourages future international collaboration with respected research facilities.

John Stegemeier is advised by Greg Lowry and co-advised by Jeanne VanBriesen in the Civil and Environmental Engineering Department at Carnegie Mellon University.