Abstract
The evaluation of biochar application on the adsorption behavior of topramezone on soil under no-tillage (NT) and rotary tillage treatments (RT) has been assessed. Fourier Transform Infra-Red Spectrometry (FTIR), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller) (BET) were used for the biochar characterization. Batch experiments were carried out in a laboratory to assess the adsorption of topramezone on soil through equilibrium and kinetic modeling under biochar addition. The clay content has been found to be higher under NT (18.24 ± 0.01) than under RT (15.91 ± 0.02). The total organic carbon was higher under NT. The topramezone adsorption equilibrium reached after 8 and 12 h, for NT and RT, respectively. The kinetic and thermodynamic analyses showed the adsorption under both treatments matched with pseudo-second-order kinetic and Langmuir models, respectively. After biochar addition, the pesticide adsorption capacity (40 < 25 < 15 °C) increased with decreasing temperature suggesting an exothermic adsorption process while negative values of Gibbs free energy (ΔG); −1848.07 and −366.531 J mol−1; for the soil under NT and RT at 25 °C, respectively, indicated spontaneous adsorption. Negative entropy values (ΔS); −21.92 and −78.296 J mol−1K−1, for NT and RT, respectively, explained a decreased randomness process. The enthalpy was higher (p < 0.05) under RT (−23,274.6 J mol−1) than under NT (−1313.73 J mol−1). Conclusively, it was shown that the topramezone adsorption capacity was higher under NT, and biochar addition increased more pesticide adsorption under NT than under RT.
Highlights
Once applied, pesticides dissipate in different compartments of the natural environment through volatilization, training to surface water by runoff, vertical transfer through soils [1] photolysis, and absorption by living organisms
The spectra of biochar were characterized at wave numbers 3431, 2909, 2302, 1622/1412, 1391/1225, 1088/1051, 784/735, 590, and 444 cm−1, which correspond to the stretching of hydroxyl (–OH), methylene
The biochar produced from maize straw residue had more effect on topramezone adsorption under no-tillage than under rotary tillage treatment
Summary
Pesticides dissipate in different compartments of the natural environment through volatilization, training to surface water by runoff, vertical transfer through soils [1] photolysis, and absorption by living organisms. Two major processes condition the fate of pesticides: degradation (biotic and abiotic) and retention by the solid soil matrix (phenomena of adsorption-desorption). A fraction of the pesticide can remain mobile in the soil solution and constitutes the so-called available fraction. The pesticide will be available for living organisms (plants, microorganisms), in this case, it is called bioavailability and for deep entrainment to groundwater, thereby generating their contamination [2]. The retention of pesticides in soils is an essential process because it regulates their persistence, bioavailability, and transfer to. Public Health 2019, 16, 5034; doi:10.3390/ijerph16245034 www.mdpi.com/journal/ijerph
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