Surface Partitioning in Organic-Inorganic Mixtures Contributes to the Size-Dependence of the Phase-State of Atmospheric Nanoparticles

Research output: Contribution to journalArticle


Atmospheric particulate matter is one of the main factors governing the Earth's radiative budget, but its exact effects on the global climate are still uncertain. Knowledge on the molecular-scale surface phenomena as well as interactions between atmospheric organic and inorganic compounds is necessary for understanding the role of airborne nanoparticles in the Earth system. In this work, surface composition of aqueous model systems containing succinic acid and sodium chloride or ammonium sulfate is determined using a novel approach combining X-ray photoelectron spectroscopy, surface tension measurements and thermodynamic modeling. It is shown that succinic acid molecules are accumulated in the surface, yielding a 10-fold surface concentration as compared with the bulk for saturated succinic acid solutions. Inorganic salts further enhance this enrichment due to competition for hydration in the bulk. The surface compositions for various mixtures are parametrized to yield generalizable results and used to explain changes in surface tension. The enhanced surface partitioning implies an increased maximum solubility of organic compounds in atmospheric nanoparticles. The results can explain observations of size-dependent phase-state of atmospheric nanoparticles, suggesting that these particles can display drastically different behavior than predicted by bulk properties only.


  • Josephina Werner
  • Maryam Dalirian
  • Marie Madeleine Walz
  • Victor Ekholm
  • Ulla Wideqvist
  • Samuel J. Lowe
  • Gunnar Öhrwall
  • Ingmar Persson
  • Ilona Riipinen
  • Olle Björneholm
External organisations
  • Swedish University of Agricultural Sciences
  • Stockholm University
  • Uppsala University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Meteorology and Atmospheric Sciences
Original languageEnglish
Pages (from-to)7434-7442
Number of pages9
JournalEnvironmental Science and Technology
Issue number14
Publication statusPublished - 2016 Jul 19
Publication categoryResearch