O ácido perfluoropropiônico e suas interações com moléculas atmosféricas: implicações para a formação de aglomerados pré- nucleação

Abstract

The ever-increasing emissions of industrial pollutants and particulate matter into the atmosphere have become a global concern. These pollutant molecules can interact with other atmospheric molecules, forming stable clusters that either participate in aerosol formation or are transported across regions. A molecular-level understanding of the composition and stability of such molec- ular clusters, as well as their contribution to the formation of secondary organic aerosols, is crucial. This is particularly relevant in light of growing evidence regarding the harmful impacts of pollutants and aerosols on both the environment and human health. A specific class of pollutants that is receiving significant attention are persistent organic pollutants (POPs), known for their long environmental lifetimes, high toxicity, and bio-accumulative potential. Among the POPs, perfluorinated compounds—especially perfluoroalkyl carboxylic acids (PFCAs , CnF2n+1COOH) warrant close study due to their widespread industrial use and their potential adverse effects on the environment and human health. In the present work, we employ high-level Density Func- tional Theory (DFT) to investigate the electrostatic interaction of perfluoropropionic acid (PFPA, C2F5COOH), a PFCA with n=2, with well-known atmospheric molecules namely water (H2O), formaldehyde (HCHO), ammonia (NH3), formic acid (HCOOH), methanol (CH3OH), sulfuric acid (H2SO4), methanesulfonic acid (MSA) and monoethanolamine (MEA). A detailed and systematic quantum-chemical calculation has been performed to explore the structural, energetic, electrical, and spectroscopic properties of various hydrogen-bonded molecular clusters mediated by PFPA. These clusters, comprising up to six monomers, are analyzed in the context of their potential role in the atmospheric pre-nucleation process. Our analysis reveals that PFPA forms stable hydrogen-bonded clusters with organic acids such as H2SO4 and MSA, which are widely recognized atmospheric nucleation precursors, as well as with atmospheric bases like NH3 and MEA. The scattering intensities of radiation (Rayleigh activities) significantly increase when PFPA clusters are formed. Analyzing the binding electronic energies and free energy changes associated with the formation of these clusters at different temperatures suggests that PFPA can participate in the initial nucleation processes and contribute effectively to new particle formation in the atmosphere. While the presence of water, at the microhydration level, does not notably affect the stability of PFPA-NH3 clusters, the simultaneous presence of both SA and MEA enhances PFPA’s interaction capacity under ambient conditions.