CHEMICAL CHARACTERIZATION AND SPECIATION OF THE SOLUBLE FRACTION OF ARCTIC PM10

The soluble fraction of atmospheric particulate matter can affect the chemistry of the atmospheric aqueous phase, such as raindrops, clouds, fog, and ice particles. Compounds such as transition metal ions are known for their (photo-)catalytic behaviour and their tendency to form complexes in solution1. This study was focused on the analysis of the soluble fraction of Arctic PM10 samples collected at Ny-Ålesund (Svalbard Islands) in 2012. The concentrations of Na+, K+, NH4 +, Ca2+, Mg2+, Mn2+, Cu2+, Zn2+, Fe3+, Al3+, Cl-, NO2 -, NO3 -, SO4 2-, PO4 3-, formate, acetate, malonate, and oxalate in water were determined by ICP-OES, SF-ICP-MS, and ion chromatography. Principal component analysis was used to describe the similitudes and seasonal differences between samples by the variability in the concentrations of the components. Speciation models were applied to define the major species that were formed in solution as a function of pH using the software PyEs2. The model highlighted (i) the presence of the main cations such as Na+, K+, Mg2+, and Ca2+ in the form of aquoions through all of the investigated pH range (2-10); (ii) Cu2+, Zn2+, and in particular Fe3+ and Al3+ are mostly present in their hydrolytic forms; (iii) Al3+, Fe3+, and Cu2+ have solid hydrolytic species that precipitate at pH slightly higher than neutrality (Figure 1). Moreover, these metals show interesting interactions with oxalate and sulphate ions. The speciation models were also run by considering the seasonal variability of the concentration of the components and at higher concentration level to better simulate the real environmental conditions. In fact, the water associated to the particulate at low temperatures is very scarce. The results highlighted the main role of oxalate as ligand in solution. The determination of thermodynamic constants at lower temperatures will be necessary to better simulate the species distribution.