JWSS - Journal of Water and Soil Science

Biochar is a soil amendment that has a high capacity to adsorb heavy metals. The aim of this study was to identify the influence of cow manure and its biochar on nickel adsorption and to determine the best models to describe the kinetics of Ni retention. Accordingly, cow manure and its biochar were added to the soils at the levels of 0, 2 and 4%, and samples were incubated for 90 days. Soil samples were equilibrated with 100 mg L-1 Ni solutions for periods of 1 to 2880 min. Then, the concentration of nickel was measured. The Ni adsorption data were fitted to seven commonly used kinetic models. The results showed that cow manure and its biochar application in all times and levels increased nickel adsorption more than the control. There was also a significant difference (P<0.05) between cow manure and its biochar. Application of 4% biochar, as compared with the same level of cow manure, and the control, increased the Ni adsorption by 23 and 44%, respectively. Power function was the best fitted model describing the patterns of Ni adsorption, as evidenced by the relatively high values of R2 and the low values of SE. However, the Elovich function had some R2 similar to that of power function, but it could not be used as an adequate function to investigate the kinetics of nickel adsorption due to their high values of SE. The zero order, the first order, the second order, the third order, and parabolic diffusion equations were not well fitted to the Ni adsorption data.

Nowadays, one of the ways to confront with the micronutrients deficiency is application of Nano materials to increase the availability of elements such as zinc for plants.  Therefore, this study was conducted to investigate the effect of functionalized iron oxide nanoparticles and zinc sulfate chemical fertilizer on the zinc chemical forms in soil solution phase and its correlation with zinc concentrations and uptake in wheat. This study was carried out in a completely randomized design with three replications. Treatment consisted of functionalized iron oxide nanoparticles of Hydroxyl (OH), Carboxyl (COOH) and Amine (NH₂), each at three levels (100, 200 and 300 mg.kg^-1), ZnSO₄ (40 kg.ha^-1) and Control (without using iron oxide nanoparticles). At the end of the cultivation period, soil chemical properties such as pH, soil available zinc and dissolved organic carbon and concentrations and the uptake of zinc in plant were measured. The results showed that pH, available zinc and dissolved organic carbon content of soil solution were significantly affected by the treatments. The results obtained from the Visual MINTEQ Geochemical model showed that the highest amount of the free form of zinc (Zn²⁺) was obtained at the level of 300 mg.kg-1 of carboxyl iron oxide nanoparticles. Also, the experimental treatments significantly influenced the concentration of Zn-DOM species. The positive and significant correlation between Zn⁺² and Zn- DOC species with the concentration and total Zn uptake of wheat indicated that these pools of Zn could be liable species in soil. The results of this study, therefore, showed that the application of functionalized iron oxide nanoparticles could help to improve soil conditions in order to increase the zinc availability for plants.