(141d) Dependence of Surface Chemistry On Environmental Fate and Transport of Metallic Nanoparticles

As research in nanotechnology becomes more prominent, nanoparticles have developed into a commercial market and are produced in large quantities. Silver nanoparticles are currently available in over 1000 consumer products and gold nanoparticles have potential in many biomedical applications such as drug delivery and bioimaging. As the amount of nanoparticles used commercially increases, the concern of their environmental consequences becomes more prudent.  To date there have been many studies conducted on nanoparticle toxicity under lab conditions, but very few studies have been conducted on  nanoparticle s in environmental settings.  Many factors contribute to the behavior of engineered and natural nanoparticles in soil, including surface chemistry, elemental composition, size and concentration. The properties of the soil also contribute to nanoparticle transport properties in soil. Soil inherently contains natural molecules such has humic acid, fulvic acid, citric acid, and desferrioxamine-B; each of which are components of natural organic matter, (NOM).  Ligand exchange is a common reaction that occurs on the surface of nanoparticles when a molecule with a higher affinity to the nanoparticle core material replaces the original surface chemistry. Ligand exchange on nanoparticle surface with natural molecules found in soil can either promote or inhibit nanoparticle transport in soil, and this is being investigated in our study.  An accelerated study was also conducted to obtain information on adsorption properties of nanoparticles to soil under saturated conditions. In short, citrate stabilized silver nanoparticles were mixed with 0.25g of sandy loam soil in 10 mL of water in concentrations of 20, 200, and 200 ppb. The pH of each solution was adjusted to 5.5. The silver content of the water phase and soil phase was measured by ICP-MS after one week to determine the fate of the nanoparticles.  The transport of nanoparticles through soil was monitored using miscible displacement column experiments. A sandy loam soil was packed in 8.3 cm x 1.5 cm (OD) columns and nanoparticle suspensions were added as a finite step of one column volume then followed by nanoparticle free groundwater simulant. The concentration of nanoparticles in the effluent was monitored and the columns were segmented after the experiments to determine nanoparticle distribution within the column. Studies will also be conducted on silver nanoparticles with a variety of surface chemistries to determine the role of surface chemistry in nanoparticle fate and transport in soil systems.