Aspect of the degradation and adsorption kinetics of atrazine and metolachlor in andisol soil

Abstract

SummaryThe degradation kinetics and sorption characteristics of atrazine and metolachlor in Japanese andisol soil were evaluated using laboratory incubation of soil samples. The water content of the soil was set to field capacity while three different temperatures (5, 25 and 35°C) were considered for the experiment. First order model fitted the degradation kinetics of both herbicides under the investigated temperature range with half-lives ranging from 19.2 to 46.9 days for atrazine and from 23.4 to 66.9 days for metolachlor, respectively. The activation energies (Ea) of atrazine and metolachlor calculated using Arhenius equation were 21.47 and 23.91 kJ mol−1, respectively. The soil sorption study was conducted using the batch equilibrium process. The adsorption behaviors of atrazine and metolachlor were investigated using linear, Freundlich and Langmuir isotherms although the linear and Freundlich isotherms gave relatively high correlation coefficient (R2) and very low standard error of estimate (SEE). The free energy (ΔG°) values were in the range −30.6 to −32.0 kJ/mol, and −32.1 to −41.5 kJ/mol for atrazine and metolachlor, respectively. Thermodynamic parameters indicated that the adsorption is spontaneous, endothermic accompanied by increase in entropy. The understanding of atrazine and metolachlor sorption processes is essential to determine the pesticide fate and availability in soil for pest control, biodegradation, runoff and leaching.

Fate of herbicides in cropped lysimeters: 2. Leaching of four maize herbicides considering different processes

“…Physicochemical and subsurface properties influence the retention of pesticides. Herbicides can, for example, sorb to clay particles or organic matter (Cox et al., 1997; Köhne et al., 2006; Weber et al., 2000), and degradation processes can influence the fate of pesticides in the subsurface (Carabias‐Martínez et al., 2002; Caracciolo et al., 2005; Jaikaew et al., 2017; Vischetti et al., 1998). Additionally, preferential flow can have substantial influence as it may induce concentration peaks in leachate water, which have been documented after strong precipitation events following pesticide application (Benettin et al., 2019; Isch et al., 2019; Radolinski et al., 2021).…”