Direct Observation of Anthracene Clusters at Ice Surfaces

• Main Authors: Subha Chakraborty (5348522), Annastacia D. Stubbs (7831757), Tara F. Kahan (2071705)
• Format: Other Non-Article Part of Journal/Newspaper
• Language: unknown
• Published: 1753
• Subjects: Biophysics; Biochemistry; Medicine; Biotechnology; Inorganic Chemistry; Infectious Diseases; Environmental Sciences not elsewhere classified; Chemical Sciences not elsewhere classified; resolved fluorescence microscopy; following lateral diffusion; experimental challenges associated; numerous surfaces within; atmospheric scientists struggle; ice present important; reconcile model predictions; covered regions due; frozen organic matter; artificial snow prepared; saltwater ice surfaces; freshwater ice surfaces; control atmospheric composition; frozen surfaces; freshwater ice; frozen freshwater; atmospheric sciences; sea ice; temperate regions; saltwater solutions; improve predictions; use wavelength; techniques used; sized clusters; reaction media; poorly understood; pollutant fate; pollutant anthracene; monomeric form; monitoring reactions; greatly alter; field observations; exposure risk; direct observation; chemical speciation; aqueous solution; anthracene ; anthracene clusters; anthracene adsorbs; Sea ice
• Online Access: https://doi.org/10.1021/jacs.1c09220.s001

Heterogeneous processes can control atmospheric composition. Snow and ice present important, but poorly understood, reaction media that can greatly alter the composition of air in the cryosphere in polar and temperate regions. Atmospheric scientists struggle to reconcile model predictions with field observations in snow-covered regions due in part to experimental challenges associated with monitoring reactions at air–ice interfaces, and debate regarding reaction kinetics and mechanisms has persisted for over a decade. In this work, we use wavelength-resolved fluorescence microscopy to determine the distribution and chemical speciation of the pollutant anthracene at environmentally relevant frozen surfaces. Our results indicate that anthracene adsorbs to frozen surfaces in monomeric form, but that following lateral diffusion, molecules ultimately reside within brine channels at saltwater ice surfaces, and in micron-sized clusters at freshwater ice surfaces; emission profiles indicate extensive self-association. We also measure anthracene photodegradation kinetics in aqueous solution and artificial snow prepared from frozen freshwater and saltwater solutions. Our results suggest that anthraceneand likely other aromatic pollutantsundergo bimolecular photodegradation at the surface of freshwater ice and sea ice, but not at the surface of frozen organic matter. These results will improve predictions of pollutant fate and exposure risk in the cryosphere. The techniques used can be applied to numerous surfaces within and beyond the atmospheric sciences.