Detecting metal-ligand complexes in atmospheric aerosols: analytical challenges and advancements Chiara Giorio 1 , Sara D’Aronco 1 , Valerio Di Marco 2 and Andrea Tapparo 2 1 Yusuf Hamied Department of Chemistry, University of Cambridge, United Kingdom, 2 Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Italy Aqueous phase processing of aerosol can lead to substantial modifications of aerosol chemical, physical and toxicological properties [1]. A process potentially very important in this context is the formation of metal-organic ligand complexes in atmospheric aqueous phases, like fog/cloud droplets and deliquescent aerosol in conditions of high humidity. Such process can increase the solubility of metals, therefore their bioavailability [2], and affect their capability to generate reactive oxygen species in lung fluids once inhaled. We investigated the formation of metal-organic ligand complexes, especially those involving cyanides and small dicarboxylic acids, in urban aerosol collected in the city centre of Padua (Italy), in the Po Valley. Aerosol samples were then characterized for quantification of both metals, using inductively coupled plasma mass spectrometry (ICP-MS), and organic ligands, using ion chromatography (IC) with conductimetric detection. Thermodynamic modelling [3], was used to gain the speciation picture of the equilibria in solution mimicking fog/cloud waters. We assessed the effects of metal-ligand complexes formation on the solubility and solubilisation kinetic of metals from the particles to aqueous solutions simulating fog and rainwater. Preliminary results show that iron, copper, and manganese are present, significantly, in the aerosol in a complexed form with organic compounds. Dissolution kinetics of many metals depended on the chemical form in which they are present in the aerosol, and they were influenced by the environmental conditions during the campaign. Direct detection of metal-ligand complexes was attempted with a wide range of techniques including Mass Spectrometry, Raman spectroscopy, and X-ray Absorption Spectroscopy for which advantages and disadvantages will be discussed. References 1. Decesari, S., Sowlat, M. H., Hasheminassab, S., Sandrini, S., Gilardoni, S., Facchini, M. C., Fuzzi, S., and Sioutas, C. Atmos.Chem. Phys., 17 , 7721‑7731 (2017). 2. Okochi, H., and Brimblecombe, P. Sci. World J., 2 , 767–786(2002). 3. Scheinhardt, S., Müller, K., Spindler, G., and Herrmann H. Atmos. Environ., 74 , 102–109 (2013).
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