Effect of Zinc Oxide Nano-Particles (ZnO) on some Physical and Chemical Properties of Soils with Different Textures

 Given the energy crisis in the world, increasing environmental pollution, clean, renewable energy and the reduction of environmental pollution are needed. Soil is the main source of agricultural production. Therefore, maintaining soil health and fertility is very important for sustainable food production. Nanotechnology is a good way to reduce soil issues in agriculture, a promising method to improve soil properties and significant capacity to increase yield. Nanotechnology is one of the newest technologies that is used in all fields of science and research due to its high potential and unique features, including natural resources and soil protection. Nanoparticles have the ability to change some physical, mechanical and chemical properties of soil due to their very high specific surface area and activity. Nanoparticles increase the cation exchange capacity of soil and soil porosity. Among all nanoparticles, zinc oxide (ZnO) is one of the most widely used nanoparticles. Zinc oxide nanoparticles due to their high specific surface area can act as a bonding agent between particles and stabilize the soil structure by flocculating soil particles. Although many studies have used zinc oxide nanoparticles (ZnO) in the field of heavy metal contamination in soil, aqueous solutions and plants, the effect of one nanoparticle on soils with different textures has been less reported. Therefore, objective of this study was to investigate the effect of zinc oxide nanoparticles on some physical and chemical properties of soils with different textures.
 In this study, three soil samples with different textures, including sandy loam, loam and clay were collected from three locations as Malayer, Abbasabad and Nahavand, in Hamedan province, respectively. Samples were taken from soil surface (0-20 cm depth). The soil samples were transferred to the Soil Physics Laboratory. After  air drying, they were passed through a 4 mm sieve and mixed with specific weight percentages of zinc oxide (ZnO) nanoparticles (zero, 0.5, 1 and 3 % W/W) in three replications. After preparing the treated samples, the soils were homogeneously poured into plastic containers measuring 18 × 5.5 × 18 cm with a specific bulk density related to the field. The treated soils in plastic containers, were wetted and dried with municipal water for 120 consecutive incubation period. After 120 days from the start of incubation, the samples were taken from the containers. Some physical and chemical properties including pH, cation exchange capacity, organic matter, calcium carbonate and electrical conductivity were measured.
 The results showed that the use of nanoparticles increased the cation exchange capacity in two textures of loamy and clay soils. The increment was significant compared to the control in loamy soil at two levels of 1 and 3% and in clay soil in all three levels of 0.5, 1 and 3%. Electrical conductivity increased and decreased (P <0.05) at 3% level for loamy soil and at 3% for sandy loam and clay soils, respectively. In contrast, the application of nanoparticles led to a decrease in pH and organic matter content (P <0.05) in sandy loam and clay soils, respectively. At the level of zero and 0.5%, the order of pH was: sandy loam> clay> loamy soil, with significant differences. But at the level of 1%, the order of pH was: sandy loamy> loamy> clay, with significant differences. At 3% level, the order of pH was: loamy> sandy loam> clay, with significant differences. At all levels of zero, 0.5, 1 and 3% of zinc oxide nanoparticles, the amount of organic matter was significantly in loamy> clay> sandy loam. Application of different levels of zinc oxide nanoparticles in clay soil reduced the percentage of calcium carbonate (P <0.05) (at the 3% by weight level), but had no effect on the amount of this variable in sandy loam and loamy soils. At all levels of zero, 0.5, 1 and 3%, the amount of soil calcium carbonate was significantly in the following order: clay> sandy loam> loam.
 According to the results obtained in this study, it can be concluded that the use of nanoparticles can be a good solution to reduce the harmful environmental effects of chemical fertilizers. In addition to the positive effect of zinc oxide nanoparticles on physical and chemical parameters in different textures, the selection of the most optimal level of zinc oxide nanoparticles should be economically applicable. This requires further studies to determine the significant effects of nanoparticles on the physicochemical properties of the soils in different conditions to determine the optimal amount of nanoparticles, in order to save costs.