Determination of Dispersion Coefficient of Deltamethrin in Short Transfer Intervals in Wheat Biochar Soil Columns

Organic matter improves the physical condition of the soil and due to the increase in water holding capacity of the soil, changes the pattern of contaminant uptake and prevents them from leaching into groundwater. Dispersion is important factor affecting soil solute transport in porous media that used in the advection-dispersion equation and it is a function of the transmission distance. The aim of this study was to investigate the effect of biochar on the leaching process of deltamethrin in soil columns. During this study, the Breakthrough curve and dispersion coefficient of this pesticide in vertical soil columns were determined.

This study was carried out in soil columns with a height of 15 and 30 cm and in a period of 12, 23, 56 and 112 days and including different levels of 1.5 and 3 WP% (Weight percent) of wheat biochar and control treatment as a completely randomized factorial design. The concentration of deltamethrin used was 300 cc per thousand liters per hectare. To determine the residual concentration, the pesticide was sprayed on the surface only once with the recommended dose and according to the considered irrigation periods, the changes of the pesticide over time and at different depths of the soil columns were studied. In this study, Brigham's analytical method was used to obtain the dispersion coefficient. Analysis of variance and comparison of means in the studied treatments was performed using LSD statistical test and SAS 9.4 software.

The results showed that the residual concentrations of pesticides in 1.5 and 3% of biochar treatments compared to the control were decreased 26 and 43%, at depths of 0 -15 cm and 37 and 17% at depths of 15-30 cm respectively. Based on the results, pesticide uptake and stabilization in 3% biochar treatment was more than other treatments. In the control treatment, with increasing soil depth, it was observed that the dispersion coefficient decreased, in the modified treatment with biochar 1.5%, the dispersion increased while in the biochar 3% treatment, the dispersion coefficient decreased significantly by increasing the sample length. Deltamethrin dispersion coefficient in 15 cm columns for control, biochar 1.5 and 3% treatments were 5.37, 1, 3.59 cm and in 30 cm columns 3.91, 1.27, 0.92 cm was obtained, respectively.

Biochar production is very convenient and cost-effective and is successful in restricting the movement and stabilization of pesticides in the soil and by increasing its weight percentage in the soil, due to the surface area of biochar can control the movement of pesticides.