Using multiconfigurational quantum chemistry, a mercury photoreduction mechanism is proposed that would explain the measurements of mercury re-emission from ice to the atmosphere, which have been poorly understood for decades.

An international research team co-led by the IQF-CSIC and the University of Valencia has discovered the mechanism by which almost all of the mercury deposited in polar ice returns to the atmosphere with the arrival of spring in the Arctic. The discovery, achieved using computational chemistry techniques and published in the journal ‘PNAS’, provides new information for understanding the biogeochemical cycle of mercury, a global pollutant and a toxic element for the nervous system of living beings. The collaborative team has been trying for years to understand the mercury cycle in the atmosphere, adding to atmospheric and climatic representations information on ‘sunlight-induced excited state chemistry’, an aspect of quantum mechanics rarely considered in current models. This work advances the need to develop mechanistic biogeochemical models to predict how mercury pollution in the Arctic will evolve in future global change scenarios. Javier Carmona-García, Alfonso Saiz-Lopez, Anoop S. Mahajan, Feiyue Wang, A. Borrego-Sánchez, A. Ulises Acuña, Carlos A. Cuevas, Juan Z. Dávalos, Aryeh Feinberg, Andrea Spolaor, Manuel F. Ruiz-López, Joseph S. Francisco, and Daniel Roca-Sanjuán. Photoreduction of mercuric bromides in polar ice. PNAS. https://doi.org/10.1073/pnas.2422885122