Testing the ability to reduce the leaching of pesticides in soil amended with agro-industrial and composted waste

Abstract

The retention potential of composted sewage sludge, orujillo (a solid residue from olive oil production), sawdust and sunflower seed shell to prevent soil leaching of atrazine, chlorfenvinphos, and chlorpyrifos was studied in open systems using fixed-bed adsorption columns. The columns were constructed from soil and the soil was amended with 10% of the organic waste cited. Pesticides were applied, and columns were subjected to simulated rainfall. Breakthrough and cumulative curves were built from pesticides detected each day in leachates, as % of applied. Our analysis reveals that the effectiveness of these amendments is not universal; it depends critically on the molecular structure of the pesticides and how it interacts with the physicochemical properties of the amendments and the soil. Orujillo emerged as the most broadly effective amendment, reducing elution peaks by up to 7.6-fold for chlorfenvinphos and significantly delaying atrazine breakthrough via lignin partitioning. Exploratory multiparametric and LASSO regression analyses identified oxygen content (%) and calcium (%) as the most influential properties controlling distribution coefficients and cumulative leaching. Furthermore, we found that amended soils require significantly greater irrigation volumes to reach equilibrium, providing a “resilience factor” against extreme rainfall events. Discrepancies between batch and column results highlight that laboratory-derived constants often fail to predict leaching under dynamic flow conditions.