Sorbent- and sorbate-influenced sorption variability and nonlinearity: a meta-analysis on chlorpyrifos with soils, sediments, and other carbonaceous materials

• Chlorpyrifos sorption shows ∼2-log variability in log K OC across geosorbents • New nonlinear sorption framework captures both sorbate and sorbent influences • Nonlinear sorbate-sorbent models perform well on diverse untrained sorbents • Findings challenge K OC constancy and stress sorbent composition’s influence Inter-sample sorption variability and nonlinearity can ambiguate fate and ecotoxicity assessment of organic pollutants and remediation strategy. Nonlinear sorption models that assume constancy in organic carbon (OC) normalized sorption coefficient ( K OC ) are often adopted across different sorbents. This study explored sorbent-side influence on sorption through meta-analysis and modeling of sorption data on chlorpyrifos, a recently Stockholm Convention enlisted non-ionizable organophosphate pesticide, and its main metabolite 3,5,6-trichloropyridinol (TCP). Log K OC varies by approximately 2 log units among soils and sediments. In predicting sorption with natural geosorbents ( n =519), linear-OC and Freundlich models are outperformed by models considering nonlinear sorbate-side (concentration) and sorbent-side (OC content) effects ( S = K O C f O C a C b or K O C f O C ϕ a C b ). All nonlinear chlorpyrifos models are C -linear but f OC -nonlinear. The resulting models predict fairly against out-of-domain (untrained) sorbents including biosolids, peat, dissolved organic matter (DOM), biochar, vegetative residues, and wood pieces with root mean squared error (RMSE) ranging from 0.17 to 0.72 ( n =304), hinting the possibility of a universal sorption model across different carbonaceous sorbents. These models capture sorbate competition and sorbent configuration , and may apply or adapt to other chemicals and carbonaceous sorbents to accommodate changing sorbent configurations, compositions, or volume/domain accessibility. Metaphysically, the proposed nonlinear models are grounded in a reference-adjustment framework, where overall effects are quantified as adjustments relative to a base-case scenario, as in thermodynamics and kinetics. Overall, results challenge K OC constancy that underlies most current models while demonstrating the importance of inter-sorbent variations in composition and configuration of organic components for accurate sorption assessment.