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 unknown. Corn, lettuce, soybean and zucchini were grown for 28Â d in two different soils (agricultural, residential) amended with 0â2000Â mg engineered nanoparticle (ENP) CeO2Â kgâ1and biochar (350Â Â°C or 600Â Â°C) at application rates of 0â5% (w/w). At harvest, plants were analyzed for biomass, Ce content, chlorophyll and lipid peroxidation. Biomass from the four species grown in residential soil varied with species and biochar type. However, biomass in the agricultural soil amended with biochar 600Â Â°C was largely unaffected. Biochar co-exposure had minimal impact on Ce accumulation, with reduced or increased Ce content occurring at the highest (5%) biochar level. Soil-specific and biochar-specific effects on Ce accumulation were observed in the four species. For example, zucchini grown in agricultural soil with 2000Â mg CeO2Â kgâ1and 350Â Â°C biochar (0.5â5%) accumulated greater Ce than the control. However, for the 600Â Â°C biochar, the opposite effect was evident, with decreased Ce content as biochar increased. A principal component analysis showed that biochar type accounted for 56â99% of the variance in chlorophyll and lipid peroxidation across the plants. SEM and Î¼-XRF showed Ce association with specific biochar and soil components, while Î¼-XANES analysis confirmed that after 28Â d in soil, the Ce remained largely as CeO2. The current study demonstrates that biochar synthesis conditions significantly impact interactions with ENP, with subsequent effects on particle fate and effects.
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