Radionuclides Binding to Organic Components at the Marine Aerosol Surface

Atmospheric release of nuclear wastewater results in the introduction of radionuclides into seawater. These radionuclides can be transported back to the atmosphere by interacting with organic matter at the surface of marine aerosol. Organic molecules, such as organic acids (OAs) and alcohols, the primary components of the organic coating on marine aerosol, play a crucial role in this process. However, the discriminated mechanisms of the interactions of these OAs and organic alcohols at the marine aerosol surface urgently need to be explored. This study uses a Langmuir trough to mimic the marine aerosol surface and investigates the interactions of several OAs (formic acid, hexanoic acid, heptanoic acid, octanoic acid, and nonanoic acid) and dodecanol at seawater-relevant ratios. It was found that upon their addition, metal ions (Ba2+, Co2+, Mn2+, Cs+, Sb3+, Sr2+, Rh3+, Ru3+, and La3+) acting as proxies of radionuclides effectively interacted with the carboxyl headgroups of OAs, which was manifested as a significant increase in the carboxylate asymmetric stretch. This asymmetric stretching vibration is significantly increased with the metal ion concentration and enrichment. Furthermore, the apparent surface binding affinity of metal ions with hexanoic acid is significantly higher than that with nonanoic acid, by a factor of ∼1.95. These findings are significant for understanding how metal ion enrichment at the air-sea interface influences the behavior and fate of radionuclides in the marine atmosphere. Additionally, this study provides new insights into the complex interactions between organic compounds and metal ions, offering valuable perspectives and methodologies for advancing research in marine chemistry and environmental science.