Interaction of zinc oxide nanoparticles with soil colloidal suspensions

The properties of soil colloids determine the interaction with nanoparticles, their behavior, and destiny in the soil environment including soil solutions. This study examines how several properties of soil colloids, including pH, phosphorus content, clay minerals, and iron oxyhydroxides, influence the interaction with zinc oxide nanoparticles (ZnO-nps). For the experimental setup, four different soils were selected from the temperate climate of central Europe, in Slovakia, exhibiting pH values ranging from 4.6 to 8.0. Two concentrations of ZnO-nps suspended in water, 20 and 200 mg Zn∙L^-1 were applied to the colloidal suspensions extracted from the soils and shaken for 24 h. Then the soil colloids were separated into three fractions, 100-1000 nm in size, 1-100 nm in size, and dissolved. Concentrations of Al, Si, Fe, Mn, P, and Zn were measured in these fractions, providing a comprehensive understanding of ZnO-NP distribution and interaction with soil colloids. The study reveals that soil pH significantly affects the distribution of Zn from ZnO-nps across different size fractions. However, the concentration of Fe, Al, and Si had an even greater impact on the concentration of dissolved Zn. Additionally, behavior of Zn following ZnO-NP application is associated with soil P content, where P may stabilize the ZnO-nps. These findings enhance the knowledge of nanoparticle behavior in various soil matrices and contribute to developing more stable, efficient, and easily useable nanoparticle-based applications in environmental science and agriculture.