Title: "Interactions Between Engineered Nanomaterials and Agricultural Crops"
Start Date: 12/11/2013 - 12:00pm
End Date: 12/11/2013 - 1:00pm
208 Hudson Hall
Jason C. White, PhD
Vice Director and Chief Scientist
Department of Analytical Chemistry
Connecticut Agricultural Experiment Station
New Haven, Connecticut
Abstract: Although nanomaterials (NM) use has increased dramatically, the risks posed to humans and the environment have been investigated only recently. The interaction between nanomaterials and crop species is an area of particular concern; two USDA-funded projects are supporting investigations into NM fate and effects in agricultural systems. Current investigations include a screening study evaluating the acute toxicity of 12 nanoparticles (NP)/NM (including bulk/ion controls) to 12 agricultural crops under hydroponic and soil-based conditions. Results to date show numerous instances of particle size-specific phytotoxicity, as well as concentration-dependent and species-specific response to NM exposure. In a mechanistic study, the toxicity and accumulation of CuO nanoparticles in corn was shown to be significantly greater than corresponding bulk/ions, and TEM-EDS confirmed the presence of NPs in both xylem and phloem sap. Separately, the effect of fullerenes, multiwalled carbon nanotubes (MWCNT) or NP Ag on co-contaminant (DDE, chlordane) accumulation by zucchini, tomato, lettuce, pumpkin, and soybean was determined in both model and soil systems. MWCNT reduced pesticide accumulation by all plants in a concentration dependent fashion, with decreases ranging from 20% to 100-fold. Fullerenes either had minimal impact on pesticide fate or in some cases, significantly increased organochlorine uptake. Nanoparticle Ag generally suppressed co-contaminant uptake by plants, likely through particle-mediated closing of key transport proteins. In final line of investigation just getting underway, NP cerium oxide and lanthanum oxide trophic transfer is being evaluated. Bulk or nanoparticle cerium or lanthanum oxide were added to soil (1000 mg/Kg) that was subsequently planted with zucchini or lettuce for 28-40d. At harvest, plant element content was determined by ICP-MS. Bulk cerium levels in plant roots, stems, leaves and flowers were 140, 0.29, 0.69, and 0.04 mg/Kg, respectively. However, preliminary data shows significantly greater cerium levels detected in all tissues when the exposure was in NP form; extraction and analysis is ongoing at this time. Select leaves (bulk or NP-exposed) were fed to crickets for 21 days. Cricket tissues will be digested for ICP-MS or fed to predatory mantids, which will then be analyzed for cerium content. To date, we have observed differential toxicity, accumulation, fate, and co-contaminant interactions of several nanomaterials relative to respective bulk particles and ions. The implications of these findings for accurately determining the fate and transport of nanomaterials in agricultural systems, as well as for exposure and risk posed to humans, will be discussed.