Phytotoxicity, uptake and transformation of nano-CeO2 in sand cultured romaine lettuce

摘要

Toxicity and uptake of nano-CeO2 (nCeO(2)) in edible vegetables are not yet fully understood. In the present study, we grew romaine lettuce in sand amended with nCeO(2). At high concentrations (1000 and 2000 mg/kg), nCeO(2) diminished the chlorophyll content by 16.5% and 25.8%, respectively, and significantly inhibited the biomass production. nCeO(2) (>= 100 mg/kg) altered antioxidant enzymatic activities and malondialdehyde levels in the plants. nCeO(2) (>= 500 mg/kg) triggered a remarkable increase of nitrate-N level in the shoots, which can be converted to toxic nitrite in humans thereby posed risk to human health. Concentration dependent accumulation of Ce in the plant tissues was observed. X ray absorption near edge spectroscopy (XANES) results indicate that Ce presented as nCeO(2) and CePO4 in the roots while as nCeO(2) and Ce carboxylates in the shoots. Chelation of ce(3+) by citric acid or precipitation of ce(3+) by PO43- reduced the translocation and toxicity of nCeO(2), indicating that release of Ce3+ played a critical role in the toxicity nCeO(2). (C) 2016 Elsevier Ltd. All rights reserved .