Atmospheric deposition of biologically relevant trace metals in the eastern Adriatic coastal area

Abstract

Aerosol (PM₁₀), bulk deposition, sea surface microlayer (SML) and underlying water (ULW) samples were collected simultaneously during a field campaign at the middle Adriatic coastal site between February and July 2019, to assess the impact of atmospheric deposition (AD) of biologically relevant trace metals (TM) (Zn, Cu, Co, Ni, Cd and Pb) on the sea surface responses in an oligotrophic coastal region. Anthropogenic emissions from continental Europe, alongside local/regional domestic heating, likely affected the concentrations of Zn, Cd and Pb in aerosols during winter-early spring, while traffic emissions during the tourist season impacted Ni, Co and Cu aerosol concentrations. Additionally, open-fire biomass burning (BB) episodes caused considerable TM concentration increases, while Saharan dust intrusion in spring led to a 10-fold increase in Co concentrations in PM₁₀ samples. These intensive episodes significantly affected the bulk deposition fluxes of TMs, showing that a small number of such extreme events, common to Mediterranean coastal areas, could be responsible for most of the AD. Enrichments and concentrations of total TMs in SML samples collected following BB events indicated that such events, along with high precipitation, influenced TM partitioning in surface water layers. We estimated that AD represents a significant source of TM to the shallow middle Adriatic coastal area, highlighting the need to further explore the atmosphere-sea surface links, to expand our understanding of the biogeochemistry of these important micronutrients and pollutants, including their impact on the aquatic community.

Keywords: Adriatic sea; Aerosol; Biomass burning; Bulk deposition; Sea surface microlayer; Trace metals.