Unveiling the multiphase fate of 2,4-dinitrophenol on aerosols: Interfacial hydration governs competing oxidation pathways and unexpected toxicity amplification

Abstract. This study elucidates the atmospheric transformation mechanisms of 2,4-dinitrophenol (2,4-DNP) using an integrated computational framework. Initial oxidation by hydroxyl radicals (•OH) and ozone (O₃) was identified as the dominant pathway, whereas the direct reaction with nitrogen dioxide radical (•NO₂) is kinetically hindered. A key mechanistic insight is that these primary reactions are inhibited by solvation effects, while nitro substituents further suppress the reaction rates, establishing a quantitative link between electronic structure and degradation kinetics. The subsequent atmospheric fate of the radical intermediate is governed by hydrogen atom abstraction (HAA) reactions with ambient oxygen (O₂) and •NO₂. Molecular dynamics (MD) simulations demonstrate that the adsorption of 2,4-DNP onto aerosol surrogates is non-monotonically modulated by interfacial hydration. Crucially, computational toxicology predicts that the ozonolysis process amplifies, rather than mitigates, environmental risk by generating secondary products with significantly enhanced mutagenicity and developmental toxicity. These findings provide mechanistic insights into the environmental risk amplification associated with nitroaromatic compounds and highlight the necessity of evaluating toxic transformation products for accurate environmental risk assessment.