Assessing the Oceanic Role in Global PCB Dynamics: Secondary Emissions and Atmospheric Contributions (1930–2018)

Persistent Organic Pollutants (POPs) are a class of chemical compounds characterized by their persistence, bioaccumulation, long-range transport, lipophilicity, and toxicity. Due to their long half-lives and widespread distribution, understanding the fate of POPs is crucial. Traditionally, oceans have been considered significant sinks for POPs, where these pollutants accumulate and are sequestered over time. However, recent studies indicate that oceans also function as secondary sources, re-emitting POPs into the atmosphere through volatilization, sea surface spray, and other air-ocean exchange mechanisms. These secondary emissions contribute significantly to the atmospheric concentrations of POPs, influencing global transport and deposition patterns. In this study, we will use the BETR - Global model to quantify oceanic secondary emissions contribution to Polychlorinated Biphenyls (PCBs) atmospheric concentrations. The model incorporates oceanic PCB concentrations, air-sea exchange dynamics, and atmospheric transport to assess the ocean’s role in the sequestration and re-emission of these pollutants. The model has run from 1930 to 2018 for two congeners, PCB-28 and PCB-153. The results indicated that the ocean’s secondary emissions contributed 45.58% and 36.62% of PCB28 and PCB153, respectively, to the atmospheric emissions. Each year, oceans have emitted 2.77 × 10⁴ and 1.18 × 10⁴ kg (annual average during 1930 - 2018) of PCB28 and PCB153 into the atmosphere. Further simulations are planned to extract basin-wise secondary emissions and their contribution to atmospheric concentration.