|Pignatello, Joseph -|
|White, Jason -|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 27, 2012
Publication Date: N/A
Technical Abstract: Engineered nanomaterials (NMs) enter agricultural soils directly as additives in agrichemical formulations1 and indirectly as contaminants in municipal sewage sludge.2 NIFA has a vested interest in developing predictive models for the fate and nanotoxicity of NMs in agroecosystems. An understanding of the interactions between engineered nanomaterials (NMs) and soil constituents, together with a comprehension of how these interactions may affect biological uptake and toxicity3 are currently lacking. Charcoal black carbon (BC) is a normal constituent of soils due to fire history, and can exist up to several percent by weight due to the emerging practice of applying manufactured charcoal (biochar) to improve soil fertility.4 The structure of BC is nanoporous and hydrophobic, properties that may favor heteroaggregation with NMs. Yet, published reports on BC-NM interactions are completely absent. We have selected four NMs likely to be found in agricultural soils and recommended for further research:5 zero-valent silver (n-Ag0), cerium oxide (n-CeO2), multiwalled carbon nanotubes (MWCNTs, 14C-labelled), and C-60 fullerene. Biochars from pecan shells and other materials will be used. The first objective is to quantify and microscopically characterize the binding and binding reversibility of NMs to macroscopic BC particles in aqueous suspensions as a function of solution composition and BC surface and pore characteristics (including the effects of weathering) with the goal of establishing a mechanistic model for these interactions. This objective will include a determination of the effect of BC addition on the retention of NMs in soil columns. A second objective is to determine the impact of BC nanostructure and weathering on the biological effects of each NM using plant (corn, soybean, lettuce, tomato) and earthworm (two species) bioassays with and without soil. The effect of biochar on plant/worm biomass, transpiration, photosynthetic potential, reactive oxygen species production, and particle accumulation will be determined. An essential goal of this objective is to determine the correlation between bioavailability and physical availability as assessed in Objective 1. The fundamental knowledge on BC-NM interactions gained by this research will help researchers, regulators and practitioners in the drive towards more sustainable agriculture. It will provide a mechanistic basis for predicting environmental fate that can potentially be extrapolated to other NMs. The fundamental knowledge gained on bioavailability of NMs to plants and earthworms, combined with fate models, will aid in the development of nanotoxicity risk assessment models. The knowledge gained will also have underlying significance in a ‘first principles’ sense for the design of safer and more effective delivery of agrichemicals and in situ remediation technologies, should they be needed. Lastly, the results could directly benefit farmers by providing added value to a product—biochar—that has already shown promise as beneficial soil amendment and carbon sink.