Fulvic acid modified ZnO nanoparticles improve nanoparticle stability, mung bean growth, grain zinc content, and soil biodiversity.

Zinc oxide nanoparticles (ZnO NPs) have emerged as a novel solution to combat Zn deficiency in agriculture. However, challenges persist regarding their Zn utilization efficiency and environmental impact. Fulvic acid (FA), as a relatively mature modified material, is a promising candidate to enhance the environmental stability of ZnO NPs. This study investigates modifying ZnO NPs with FA to improve their stability and increase Zn content in mung bean fruit and explores their effect on plants and the soil ecosystem. We combined FA and ZnO NPs (FZ-50) at mass ratios of 1: 5, 1: 2, and 4: 5, denoted as 20 % FZ, 50 % FZ, and 80 % FZ, respectively. Initial germination tests revealed that the 50 % FZ treatment improved sprout growth and Zn content and minimized agglomeration the most. A subsequent pot experiment compared FZ-50 with ZnO, ZnO NPs, and F + Z (1: 1 FA: ZnO NPs). Notably, the FZ-50 treatment (50 % FZ applied to the soil) demonstrated superior results, exhibiting a 30.25 % increase in yield, 121 % improvement in root nodule quality, and 56.38 % increase in Zn content, with no significant changes in enzyme activities (catalase and peroxidase). Furthermore, FZ-50 increased soil available Zn content and promoted soil microorganism diversity, outperforming ZnO and ZnO NPs. This study underscores the potential of FA as a relatively mature material for modifying ZnO NPs to increase grain Zn content, presenting a novel approach to addressing Zn deficiency in agriculture.

Nutrient strengthening of winter wheat by foliar ZnO and Fe3O4 NPs: Food safety, quality, elemental distribution and effects on soil bacteria.

With the anticipated application of engineered nanomaterials (ENMs) as foliar fertilizers in agriculture, there is a particular need to accurately assess crop intensification capacity, potential hazards, and effects on the soil environment when ENMs are applied alone or in combination. In this study, the joint analysis of scanning electron microscopy (SEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) showed that ZnO NPs transformed on the leaf surface or within the leaf, and Fe3O4 NPs were able to translocate from the leaf (~ 25 memu/g) into the stem (~ 4 memu/g), but were unable to enter the grain (below 1 memu/g), guaranteeing food safety. Spray application of ZnO NPs significantly improved grain Zn content of wheat (40.34 mg/kg), whereas Fe3O4 NPs treatment and Zn + Fe NPs treatment did not significantly improve grain Fe content. According to the micro X-ray fluorescence of wheat grains(µ- XRF) and physiological structure in situ analysis showed that ZnO NPs treatment and Fe3O4 NPs treatment could increase the elemental contents of Zn and Fe in the crease tissue and endosperm components, respectively, while antagonism was observed in the grain treated with Zn + Fe NPs. The 16S rRNA gene sequencing results showed that the Fe3O4 NPs treatment had the greatest negative effect on soil bacterial community, followed by Zn + Fe NPs, and ZnO NPs showed some promotion effect. This may be caused by the significantly higher elemental contents of Zn/Fe in the treated roots and soils. This study critically evaluates the application potential and environmental risks of nanomaterials as foliar fertilizers and is instructive for agricultural applications of nanomaterials alone and in combination.

Effects of short-term soil exposure of different doses of ZnO nanoparticles on the soil environment and the growth and nitrogen fixation of alfalfa.

The extensive application of nanomaterials has increased their levels in soil environments. Therefore, clarifying the process of environmental migration is important for environmental safety and human health. In this study, alfalfa was used to determine the effects of different doses of ZnO nanoparticles (NPs) on the growth of alfalfa and the soil environment. Results showed that the alfalfa biomass was inversely proportional to the exposure concentration of ZnO NPs. The Zn concentration in the alfalfa tissue and the exposure dose presented a significant positive correlation. A high concentration of ZnO NPs decreased the nitrogen-fixing area of root nodules while the number of bacteroids and root nodules, which in turn affected the nitrogen-fixing ability of alfalfa. At the same time, it caused different degrees of damage to the root nodules and root tip cells of alfalfa. A high dose of ZnO NPs decreased the relative abundance and diversity of the soil microorganisms. Therefore, short-term and high-dose exposure of ZnO NPs causes multiple toxicities in plants and soil environments.