Exploring links between the atmospheric water and trace element cycles in the Kara and Laptev Seas

The atmosphere is an important reservoir for the essential elements selenium (Se) and sulfur (S) as well as for the toxic element arsenic (As). Atmospheric deposition is a source of these elements to terrestrial and marine environments, which can affect ecosystems and human health. The mobility and bioavailability of Se, S, and As in surface environments depend on their chemical forms (speciation). The factors that determine elemental speciation in atmospheric deposition are likely controlled by the speciation of these elements at the source (atmospheric emissions) and by their (bio)chemical transformations during transport. In addition, atmospheric transport of trace elements and their deposition patterns might be strongly linked to the atmospheric water cycle in particular cloud and precipitation formation, because wet deposition during precipitation is an important removal mechanism of trace elements from the atmosphere. To investigate the dynamical processes that govern the cycles of atmospheric water and trace elements in polar regions, including their sources, transport pathways, and sinks, we performed various chemical measurements (total element concentrations and speciation of Se, S and As) on atmospheric samples collected during the Arctic Century Expedition in the Kara and Laptev Seas (August-September 2021). Notably, trace element analyses were combined with a 4-week continuous time series of ship-based measurements of the isotopic composition of water vapour (i.e., δ²H and δ¹⁸O). Air parcel backward trajectories were used to identify atmospheric transport patterns of elemental and water isotope signatures, based on three-dimensional wind fields from the ERA5 atmospheric reanalysis dataset. Based on our chemical and meteorological observations and transport diagnostics, we present new insights into the variability of Se, S, and As concentration and speciation in atmospheric deposition and how they are linked to the atmospheric polar water cycle.