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Metal Ion Release from Fine Particulate Matter Sampled in the Po Valley to an Aqueous Solution Mimicking Fog Water: Kinetics and Solubility

Category: Aerosol and Atmospheric Chemistry

Volume: 20 | Issue: 4 | Pages: 720-729
DOI: 10.4209/aaqr.2019.10.0498
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To cite this article:
Di Marco, V., Tapparo, A., Badocco, D., D’Aronco, S., Pastore, P. and Giorio, C. (2020). Metal Ion Release from Fine Particulate Matter Sampled in the Po Valley to an Aqueous Solution Mimicking Fog Water: Kinetics and Solubility. Aerosol Air Qual. Res. 20: 720-729. doi: 10.4209/aaqr.2019.10.0498.

Valerio Di Marco, Andrea Tapparo, Denis Badocco, Sara D’Aronco, Paolo Pastore, Chiara Giorio

  • Department of Chemical Sciences, University of Padova, 35131 Padova, Italy

Highlights

  • Metal ions leach from PM2.5 into fog water with half times around 10–40 minutes.
  • The leaching process was described by a first order kinetics.
  • A fraction of the metal ions instantly leached following contact with fog water.
  • Metal ion solubilisation may have started in atmospheric aqueous phases.

Abstract

Metals are among the key aerosol components exerting adverse health effects. Their toxic properties may vary depending on their chemical form and solubility, which can be affected by aqueous processing during aerosol atmospheric lifetime. In this work, fine particulate matter (PM2.5) was collected in the city centre of Padua in the Po Valley (Italy), during a winter campaign. Part of the sampling filters were used to measure the kinetics by which metal ions and other elements can leach from PM2.5 to an aqueous solution mimicking fog water in the winter in temperate climate regions (pH 4.7, 5°C). The leaching process was interpreted by a first order kinetics, and the fitting of the experimental data allowed to obtain the leaching kinetic constants and the equilibrium concentrations (i.e., at infinite time) for all elements. The remaining filter parts were mineralised, through two subsequent extraction steps, and the extracts were analysed by ICP-MS to gain the total elemental content of PM for a large number of elements. We found that elements can leach from PM with half times generally between 10–40 minutes, which is a timescale compatible with atmospheric aqueous processing during fog events. For instance, aluminium(III) in PM2.5 dissolved with an average k = 0.0185 min–1, and t1/2 = 37.5 min. Nevertheless, a fraction of each element was immediately solubilised after contact with the extraction solution suggesting that metal ion solubilisation may already had started during particle lifetime in the atmosphere.

Keywords

Metals PM2.5 Fog Leaching kinetics Urban air quality ICP-MS


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