Mercury in Atmospheric Air and Precipitation at the Monitoring Station Listvyanka (Southern Baikal Region) in 2022–2023

Gaseous elemental mercury (GEM) is the predominant form of mercury in the atmosphere. As a result of deposition, it enters terrestrial and aquatic ecosystems, where it is further transformed into the ecotoxicant methylmercury. The work studies GEM in atmospheric air and total mercury in atmospheric precipitation in the Southern Baikal region. Sampling was carried out at Listvyanka monitoring station (51.9° N, 104.4° E) in 2022–2023. The concentrations of mercury in air was measured with a RA-915AM mercury gas analyzer (St. Petersburg, Russia); the concentration of total mercury in precipitation was determined by PND F 14.1:2:4.271-2012 method A (permanganate mineralization) technique. The measured concentrations were statistically analyzed. During the period under study, the concentration of GEM in atmospheric air averaged 1.61 ng/m³; the pair correlation coefficient was 0.47 between Hg⁰ and sulfur dioxide (SO₂) and 0.44 between Hg⁰ and nitrogen dioxide (NO₂); a strong positive correlation (>0.9) between Hg⁰, SO₂, and NO₂ was found in 12 cases. For each episode of mercury concentration above 2.0 ng/m³, back trajectories of air masses were calculated using the HYSPLIT model. The trajectory analysis also confirmed our assumption of a common type of sources of mercury and trace gases. The weighted average content of total mercury in precipitation is 44 ng/L, the median value is 29 ng/L, and the maximum is 282 ng/L. The results supplement the existing ideas about mercury content in the atmosphere of the Southern Baikal region and show the mercury content in atmospheric precipitation on the Baikal shore to be comparable with the results obtained in urban agglomerations of Nepal, Canada, Korea, and China despite the significant distance of the measurement site from large cities.