Exposure of agricultural crops to nanoparticle CeO2 in biochar-amended soil

Authors: SERVIN, ALIA - Connecticut Agricultural Experiment Station; DE LA TORRE ROCHE, ROBERTO - Connecticut Agricultural Experiment Station; CASTILLO, HIRAM - European Synchrotron Radiation Facility; PAGANO, LUCA - University Of Massachusetts; HAWTHORNE, JOSEPH - Connecticut Agricultural Experiment Station; MUSANTE, CRAIG - Connecticut Agricultural Experiment Station; PIGNATELLO, JOSEPH - Connecticut Agricultural Experiment Station; Uchimiya, Sophie; WHITE, JASON - Connecticut Agricultural Experiment Station

Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2016
Publication Date: 6/2/2016
Citation: Servin, A.D., De La Torre-Roche, R., Castillo-Michel, H., Pagano, L., Hawthorne, J., Musante, C., Pignatello, J., Uchimiya, M., White, J.C. 2017. Exposure of agricultural crops to nanoparticle CeO2 in biochar-amended soil. Plant Physiology and Biochemistry. 110:147-157.

Interpretive Summary: There is a general speculation especially outside of the scientific community that biochar takes up small molecules and particles like a sponge. This study examined such claim by studying the influence of biochar on the uptake of nanoparticles (nanoceria) by corn, lettuce, soybean, and zucchini. Biochar generally had little effects on the update of nanoceria by the food crops. Surface interaction mechanisms will be described in this and subsequent studies.

Technical Abstract: Biochar is seeing increased usage as an amendment in agricultural soils but the significance of nanoscale interactions between this additive and engineered nanoparticles (ENP) remains largely unknown. In the present study, corn (Zea mays), lettuce (Lactuca sativa), soybean (Glycine max) and zucchini (Cucurbita pepo) were grown for 28 d in two soils (agricultural, residential) amended with 0-2000 mg nanoparticle (NP) CeO2 kg-1 and biochar (350°C or 600 °C) at application rates of 0-5% (w/w). At harvest, plants were analyzed for biomass, Ce content, chlorophyll and lipid peroxidation. Plant biomass from the four plant species grown in residential soil at biochar 350º C and 600º C varied with species and char type. However, growth in the agricultural soil amended with biochar 600 º C was largely unaffected by char presence. Biochar co-exposure had minimal impact on Ce accumulation, with most instances of reduced or increased content occurring at the highest (5%) amendment level. However, both soil-specific and biochar-specific effects on Ce accumulation were observed in the four plant species. For example, zucchini grown in an agricultural soil with 2000 mg CeO2 kg-1 ENPs and 350°C biochar at 0.5 and 5% accumulated greater Ce than did soils not amended with biochar. However, for the 600°C biochar, the opposite effect was evident, with significant decreases in Ce content observed with increasing biochar level. A principal component analysis (PCA) was used to determine total chlorophyll and lipid peroxidation variances among treatments. Results from chlorophyll analysis showed that biochar variety (350°C and 600 °C) accounted for 66-85% of the variance across the 4 species. Similarly, PCA from lipid peroxidation data showed that biochar type (350°C or 600°C) accounted for 56-99%of the variance in in the plants. SEM and µ-XRF analyses showed Ce association with specific biochar and soil components, while µ-XANES analysis confirmed that after 28 d in soil, the Ce remained largely as CeO2. The current study demonstrates that biochar synthesis conditions may significantly impact interactions with engineered nanoparticles, with subsequent impacts on ENP fate and effects.