How do certain atmospheric aerosols affect Cu-binding organic ligands in the oligotrophic coastal sea surface microlayer?

• Published in: Environmental science--processes & impacts 2024-01, Vol.26 (1), p.119-135
• Main Authors: Strme ki, Sla ana, Dešpoja, Iva, Penezi, Abra, Milinkovi, Andrea, Alempijevi, Saranda Bakija, Kiss, Gyula, Hoffer, András, Miti, Bo ena, Hruševar, Dario, Frka, Sanja
• Format: Article
• Language: English
• Subjects: Aerosols; Aerosols - analysis; Atmospheric aerosols; Binding; Biomass burning; Chemical analysis; Chemical speciation; Coastal waters; Coastal zone; Copper; Dust; Dust - analysis; Ligands; Nutrients; Pollen; Pollination; Seawater; Speciation; Surface microlayers; Trace metals; Water; Water analysis
• ISSN: 2050-7887; 2050-7895
• DOI: 10.1039/d3em00415e

It is still unclear how the chemical speciation of Cu in surface seawater is impacted by aerosols from various sources deposited on the sea surface, which is surprising, considering the environmental importance of Cu. Therefore, we used voltammetry to investigate Cu complexing capacity (CuCC) in the sea surface microlayer (SML) and in the underlying water (ULW) of the oligotrophic middle Adriatic Sea during February-July 2019. The focus was on the impacts of specific atmospheric processes such as open-fire biomass burning (BB), pollination season and Saharan dust intrusion. The presence of ligand class L 2 (19.9-392.0, average 63.8, median 43.1) nM; log  K 2 (8.3-10.2, average 9.6, median 9.6) was observed in all samples, while ligand class L 1 (40.5-76.1, average 53.6, median 48.9) nM; log  K 1 (10.3-11.1, average 10.6, median 10.5) was found in only 25% of SML samples. Throughout the period, the SML was enriched with organic ligands by a factor of up to 9.1 compared to the ULW, mainly due to the high sensitivity of the SML to specific atmospheric depositions. In addition, measurements with corresponding specific model aerosols were conducted to analyse their impacts on CuCC. Pollen directly affected CuCC in the SML by increasing the concentration of allochthonous ligands such as proteins. The deposition of BB aerosols rich in nutrients and trace metals stimulated the biological production of organic ligands, showing an indirect effect on CuCC delayed by up to two weeks. Finally, Saharan dust had a negligible impact on CuCC. This study illustrates the susceptibility of oligotrophic coastal area to the effects of pollen and open-fire BB aerosols in altering the Cu-binding organic ligands in the SML. We showed that oligotrophic coastal marine areas are susceptible to the deposition of pollen and aerosols from open-fire biomass burning, which alter Cu-binding organic ligands in the sea surface microlayer.