Chiara Giorio is Professor of Atmospheric Chemistry at the Yusuf Hamied Department of Chemistry, University of Cambridge (UK). Chiara graduated in Chemistry in 2008 from the University of Padua (Italy), where she remained for her PhD in Molecular Sciences (awarded in 2012). She was a postdoc at the University of Cambridge in the group of Professor Markus Kalberer until 2016, a researcher at the French National Centre for Scientific Research (CNRS) in 2017, and tenure-track Assistant Professor at the University of Padua until the beginning of 2020, when she returned to Cambridge. She is now leading a multidisciplinary research group working on air quality and climate science. She is the recipient of the 2021 RSC Environment, Sustainability & Energy Division Early Career Award and a Fellow of the Community for Analytical Measurement Science (CAMS).
About 0.2% of the Earth’s water is in the atmosphere. Rain, fog, clouds and deliquescent aerosols create a water phase that can shift the reactivity of volatile and non-volatile species to form new products that would not otherwise form from gas phase reactions. A notable example of processes promoted by aqueous environments is coordination chemistry. Such process leads to the formation of metal-ligand complexes between different species in the aerosols, and it can increase the solubility of particle-bound metals, therefore their bioavailability, and their capability to generate reactive oxygen species.
We investigated the formation of metal-organic ligand complexes, especially those involving small dicarboxylic acids, in urban aerosol collected in the city centre of Padua, in the Po Valley (Italy), in marine aerosol from a remote coastal environment in Henties Bay (Namibia), and in volcanic aerosol collected from the summit of Mt Etna (Italy). Aerosol samples were then characterised for quantification of metals, using inductively coupled plasma mass spectrometry (ICP-MS) and inorganic and organic ligands, using ion chromatography (IC) with conductimetric detection. The model E-AIM was used to calculate the aerosol liquid water content and the pH of the aerosols. Thermodynamic modelling, using Visual MINTEQ, was used to gain the speciation picture of the equilibria in solution in the deliquescent aerosol phase. Synchrotron-based X-ray absorption spectroscopy (XAS) was used to directly determine the oxidation state and chemical coordination sphere of iron.
For urban samples, we assessed the effects of metal-ligand complexes formation on the solubility and solubilisation kinetic of metals from the particles to both fog waters and a surrogate lung fluid. We found contrasting results in terms of solubilities and dissolution kinetics in the two aqueous environments studied. Finally, we exposed pulmonary cells to metals in different chemical forms to assess their toxicity, as well as determined their oxidative potential and their ability to promote protein aggregation linked to the development of neurodegenerative diseases.
