Abstract
The effect of volatile organic compounds (VOCs) on chromium-containing atmospheric particles remains obscured because of difficulties in experimental measurements. Moreover, several ambiguities exist in the literature related to accurate measurements of atmospheric chromium concentration to evaluate its toxicity. We investigated the interaction energies and diffusivity for several VOCs in chromium (III)-containing atmospheric particles using classical molecular dynamics simulations. We analyzed xylene, toluene, ascorbic acid, carbon tetrachloride, styrene, methyl ethyl ketone, naphthalene, and anthracene in Cr(III) solutions, with and without air, to compare their effects on solution chemistry. The interaction energy between Cr(III) and water changed from 48 to 180% for different VOCs, with the highest change with anthracene and the lowest change with naphthalene. The results revealed no direct interactions between Cr(III) particles and the analyzed volatile organic compounds, except ascorbic acid. Interactions of Cr(III) and ascorbic acid differ significantly between the solution phase and the particulate phase. The diffusion of Cr(III) and all the VOCs also were observed in a similar order of magnitude (~ 10−5 cm2/s). The results can further assist in exploring the variation in chromium chemistry and reaction rates in the atmospheric particles in the presence of VOCs.
Highlights
Simulation methodologyIn order to explore the physico-chemical interactions of Cr(III) with volatile organic compounds (VOCs) in the atmospheric conditions and its variation from the solution chemistry, several simulations were designed systematically
The effect of volatile organic compounds (VOCs) on chromium-containing atmospheric particles remains obscured because of difficulties in experimental measurements
Several volatile organic compounds and poly aromatic compounds including xylene, toluene, styrene, methyl ethyl ketone, carbon tetrachloride, ascorbic acid, naphthalene, and anthracene were selected for the analysis
Summary
In order to explore the physico-chemical interactions of Cr(III) with VOCs in the atmospheric conditions and its variation from the solution chemistry, several simulations were designed systematically. Water, Cr3+ ion, and either of the volatile organic compounds were inserted randomly in a box with size 5 × 5 × 5 n. 2, ratio 78:22) was placed in alternate systems to explore and compare Cr(III)/VOC interactions in the atmosphere, than those within the solution environment. We chose to simulate the systems with ten molecules of Cr(III) and ten molecules of volatile organic compounds (~ 133 mM in water). The diffusion coefficients and radial distribution functions were obtained from the simulation results using GROMACS and Visual Molecular Dynamics (VMD).
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