Adsorption and Desorption Behaviors of Spirotetramat in Various Soils and Its Interaction Mechanism

Abstract

Spirotetramat is a pesticide with bidirectional systemicity and can effectively control pests by inhibiting the biosynthesis of fatty acids. In this study, adsorption and desorption behaviors of spirotetramat in six soils and its interaction mechanism were studied using the batch equilibrium method and infrared radiation. The results showed that the adsorption and desorption behaviors of spirotetramat conformed to the Freundlich isotherm model. The values of adsorption capacities K F‑ads ranged from 2.11 to 12.40, and the values of desorption capacities K F‑des varied from 2.97 to 32.90. From the hysteresis coefficient, spirotetramat was easily desorbed from the test soils. The adsorption capacity of the soil to spirotetramat enhanced with an increasing temperature. Moreover, the changes in pH values and exogenous addition of humic acid and surfactant could also affect soil adsorption capacity, but for desorption, there was no correlation.

Sorption hysteresis on soils and sediments: Using single‐point desorption isotherms to obtain characteristic free energy values

“…values were even slightly negative at lower solute concentrations, which indicates that the DI was positioned here below the SI, most probably due to a lack of SDH in this region. For these three selected soils, the g ΔG ext S values increased in the following order: clay < clay loam < loam; the clay content and the soil pH decreased in the same order (Chen et al, 2018). Obviously, multiple factors may result in the above differences in the g ΔG ext S values and it is not the aim of this work to reexamine the original publication.…”

“…In that case, ferrihydrite-OM interactions may be responsible for the stronger resistance of OM perturbed during metalaxyl sorption to "relaxing" during fungicide desorption. Chen et al (2018) examined the behaviour of the bidirectional systemic insecticide spirotetramat in sorptiondesorption experiments in a series of soils. In the soils studied, the pH of the soil solutions varied between 4.4 and 8.2, such that this insecticide, having a pK value of 10.7 (Fischer & Weiss, 2008;Jeschke, 2016), did not ionize in the solutions.…”

“…The pK values of strongly acidic groups of humic substances may vary across the 2-5.5 range (Leenheer, Wershaw, Brown, & Reddy, 2003) and the multiple extracted humic substances showed a protonation/ionization range that was even more narrow (i.e., between 3.5 and 4.6; IHSS, Acidic Functional values. In the original work (Chen et al, 2018), structural soil changes induced by pH were also mentioned as a factor influencing compound-soil interactions.…”

“…Despite the strong association between these quantities, their potential usefulness differs in this example. It would be hardly possible, based just on magnitudes of the HI values, to question a probability of certain hysteresis mechanisms (e.g., the one associated with F I G U R E 6 Molar extra Gibbs free energy associated with sorption-desorption hysteresis (SDH) and obtained from sorption isotherms (SIs) and the single-point desorption isotherms (DIs) for spirotetramat on the three soils (Chen et al, 2018) plotted against the compound concentration in the equilibrated solutions from which desorption started. In the legend, the value next to the type of each soil indicates its pH irreversible soil matrix/pore deformations yet allowing a free sorbate exchange on modified sorption sites).…”

Spirodiclofen ether derivatives: semisynthesis, structural elucidation, and pesticidal activities against Tetranychus cinnabarinusBoisduval, Aphis citricolaVan der Goot and Mythimna separataWalker

“…1) and spirotetramat ( 3 , Fig. 1) possess a unique mode of action which can inhibit acetyl‐coenzyme A carboxylase (ACCase) by targeting lipid biosynthesis 10–13 . Recently, pests resistance to spirodiclofen and spiromesifen, and cross‐resistance to other acaricides have been reported 14,15 .…”