Characterization of the molecular interaction between acetaldehyde and phenanthrene: A molecular simulation study of nanoparticle formation dynamics from bioethanol blends

Abstract

Bioethanol has been increasingly applied as a renewable energy component in combination with gasoline for the reduction of emissions and to reduce the release of climate gases in the atmosphere. Blending of bioethanol and gasoline has however not been studied from a toxicological perspective, and our recent studies show that it can contribute to increased toxicity in urban atmospheres. In parallel, it is established that the combination of bioethanol and gasoline introduces two leading toxic components in the urban atmosphere as potentially toxic mixtures: acetaldehyde and PAHs. PAHs are found in combusted gasoline and are virtually absent in emissions of bioethanol. Bioethanol however, contributes with acetaldehyde, which is a potential carcinogen. In this study, we are aiming on studying the dynamics of particle formation between acetaldehyde and phenanthrene, which is a PAH found at high concentrations in generic fossil fuel emissions. Our analysis resolves the interaction of these two main emission toxic components at the molecular level in virtual chambers of 300 to 700K, under standard atmospheric conditions and under high pressure and temperature from the engine and exhaust pipe and reveals also their interaction with environmental humidity, modeled as single-point charged water molecules. The results show so far that PAHs and phenanthrene can combine in water phase and form aqueous nanoparticles which can be easily absorbed in the lungs through respiration. Water droplets in moisture becomes potential carriers of PAHs to the exposed subjects by forming non-covalent bonds with acetaldehyde, which in turn binds phenanthrene via its hydrophobic group.