Effect of Soil Texture, Nanoparticle Size, and Incubation Period on the Dissolution of ZnO Nanoparticles

Zinc is an essential plant and human nutrient and its primary source is Zn-rich food consumption. The only way to enrich plants with Zn is through the application of Zn fertilizers including various chemical and organic sources of ZnO nanoparticles (NPs). The Zn bioavailability from ZnO NPs must be considered for their recommendation as a fertilizer, and very little is known about the efficacy of such fertilizers in the Hungarian soil environment. In the present investigation, we prepared ZnO NPs of different sizes and applied them in two distinct textures of soils (sandy loam (SL) and silty clay (SC)) in an incubation experiment. The prepared ZnO NPs were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). ZnO NPs were applied in both soil types at 500 mg L−1 in the form of a suspension, and ZnSO4 was applied in the form of a solution. The soils were incubated for 7 and 14 days. Column leaching was performed to analyze the dissolved Zn. Retained Zn in the soil matrix was extracted using 0.05 M EDTA. The results showed that approximately 21–23% and 10–13% higher Zn was observed in the pore water of SL and SC soils, respectively, when spiked with small-sized NPs compared to large-sized NPs, while 14–26% higher dissolved Zn was observed in SL soil compared to SC soil. It is concluded that the size of NPs and the soil texture are the main factors that play important roles in deciding the fate of NPs under an alkaline soil environment.