Work

QSAR modelling for predicting adsorption of Sulfonylurea herbicides in agricultural volcanic ash-derived soils

Year: 2026

Type: article

Abstract: This study developed an OECD-aligned QSAR model with an explicit applicability domain to predict the adsorption of Sulfonylurea (SUs) herbicides and methabenzthiazuron in agricultural volcanic ash-derived soils (VADS), a variable-charge system poorly represented in current pesticide adsorption QSAR models. Twenty-four SUs and methabenzthiazuron were evaluated in ten VADS, generating 250 compound–VADS systems from batch adsorption–desorption experiments. The dataset was complemented by soil physicochemical characterization, adsorption kinetics, and adsorption-desorption analysis, and descriptor-based QSAR modelling using a Lamarckian Genetic Algorithm for variable selection and 𝑅 𝑖 𝑑 𝑔 𝑒 regression across interaction, soil-specific, and herbicide-specific edaphic scenarios, with external validation and domain of applicability ( 𝐷 𝐴 ). Adsorption was consistently nonlinear, and the Freundlich model best described equilibrium behavior. Across the 250 systems, 𝐾 𝑓 ⁡ ( 𝑎 𝑑 𝑠 ) ranged from 0.04 to 519.50, 𝐾 𝑓 ⁡ ( 𝑑 𝑒 𝑠 ) from 0.24 to 229.91, and the hysteresis coefficient ( 𝐻 ) from 0.00 to 0.94, indicating strong variability in retention and reversibility. The interaction scenario provided the main predictive result: with 210 training and 40 external observations ( 𝑄 2 𝐿 𝑂 𝑆 𝑂 = 0.438, 𝑄 2 𝑡 𝑒 𝑠 𝑡 = 0.347, 𝑅 𝑀 𝑆 𝐸 𝑡 𝑒 𝑠 𝑡 = 0.492, and 30/40 (75%) 𝐷 𝐴 coverage). The final QSAR interaction retained 24 descriptors, indicating that adsorption in VADS is governed by the interplay between herbicide ionisation/polarity and 3D electronic features as well as soil organo-mineral reactive domains ( 𝑂 𝑀 , 𝐶 / 𝑁 , 𝐹 𝑒 , 𝐶 𝑢 , 𝑆 , and 𝑃 − 𝑂 𝑙 𝑠 𝑒 𝑛 ). Accordingly, the predictive signal arose from herbicide-soil coupling rather than from molecular or edaphic properties alone. Within its calibrated chemical and edaphic space, the QSAR model provides a mechanistically interpretable, exploratory screening tool for identifying higher-mobility SUs–VADS combinations.

Source: Ecotoxicology and Environmental Safety

DOI: 10.1016/j.ecoenv.2026.120717