Assessment of Phytotoxicity and Behavior of 1-Year-Aged Zn in Soil from ZnO Nanoparticles, Bulk ZnO, and Zn Sulfate in Different Soil-Plant Cropping Systems: from Biofortification to Toxicity

s This study evaluated the impact of aged ZnO NPs on soil-plant systems compared to bulk ZnO and ZnSO 4 . Green pea and beetroot were grown under greenhouse conditions in two agricultural soils to which 20 mg Zn kg −1 and 225 mg Zn kg −1 had been applied 1 year before to a previous crop. At the high dose, differences in soil extractable Zn (CaCl 2 and diethylene triaminepentaacetic acid (DTPA)) were observed between Zn sources. Both ZnO applications and ZnSO 4 showed different trends in extractability over time suggesting dissolution of ZnO during crop growth. Plants accumulated large amounts of Zn in their aboveground parts with root-to-stem transfer factors of up to 5.4. Under acidic conditions, beet plants did not survive the high dose, while pea plants showed a dramatic decrease in growth (85%) and grain yield (96%). ZnO NPs differentially affected Zn accumulation and distribution within the plant tissues, but not plant growth. Weathered ZnO NPs did not seem to pose any greater potential risk to the environment than their Zn counterparts.