Location: Commodity Utilization ResearchTitle: Nanoscale Interactions between Engineered Nanomaterials and Black Carbon (Biochar) in Soil ) Author
Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 12/11/2013
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: An understanding of the interactions between engineered nanomaterials (NMs) and soil constituents, and a comprehension of how these interactions may affect biological uptake and toxicity are currently lacking. Charcoal black carbon is a normal constituent of soils due to fire history, and can be present at up to several percent by weight through the emerging practice of applying manufactured charcoal (biochar) to improve soil fertility. The structure of black carbon is nanoporous and hydrophobic, properties that may favor heteroaggregation with NMs. However, published reports on black carbon-NM interactions are completely absent. A series of pecan shell biochars were prepared at 300 – 700 oC, fully characterized, and tested in the presence of commercial nC60 and fully-characterized commercial n-CeO2 or synthesized n-CeO2 by room-temperature and hydrothermal methods. Attachment of stir-dispersed colloidal nC60 on a series of biochar samples was investigated by separately measuring soluble and biochar-associated nC60 using HPLC after 1 wk equilibration. These experiments indicated that (i) porosity, (ii) DOC, and (iii) density of biochar controlled its ability to uptake stir-dispersed nC60. Biochar-born surfactants could disperse nC60, and smaller-sized nC60 was more easily taken up by the biochar. Aldrich n-CeO2 nanoparticles averaging 190 nm in 0.5 mM citrate used as an NOM surrogate were equilibrated at pH 7.6-7.7 with different amounts of biochar. Suspensions consistently showed more elemental Ce than biochar-free blanks, suggesting biochar inhibits settling of n-CeO2. The effect of biochar added to soil at 0, 0.5, and 5% on the toxicity and accumulation of cerium oxide nanoparticles (0-2000 ug/g) by soybean was determined. After one month of exposure, biomass (tissues and total), pigment production (chlorophyll A and B, cartenoids), and cerium content of the tissues by ICP-MS was determined as a function of treatment. In general, there were minimal effects of biochar presence on cerium uptake or plant biomass; in several instances, the trend was for decreased uptake with char presence there were no effects of statistical significance. Perhaps the most interesting finding was a significant decrease in pigment content/production upon ceria exposure. This is particularly interesting given the lack of biomass effects.