AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Atmospheric Chemistry of Sea Salt Particles Internally Mixed with Secondary Organic Material: Surprising Reactivity of NaCl with Weak Organic Acids
Alexander Laskin, BINGBING WANG, Alla Zelenyuk, Jacqueline Wilson, John Shilling, Rahul Zaveri, Jerome Fast, Alexei Tivanski, Mary Gilles, Ryan Moffet, Steven Kelly, Nigge Pascal, Pacific Northwest National Laboratory
Abstract Number: 620 Working Group: Aerosol Chemistry
Abstract Chemical imaging analysis of internally mixed NaCl and secondary organic material particles was performed using complementary techniques of electron microscopy-EDX microanalysis, synchrotron based X-ray spectro-microscopy, micro-FTIR spectroscopy, and single-particle mass spectrometry. Substantial chloride depletion and formation of organic salts were observed, along with distinctive changes in particle internal composition and morphology. We present field evidence, corroborated by laboratory experiments, indicating that chloride components in sea salt particles may effectively react with organic acids releasing HCl gas to the atmosphere, leaving behind particles depleted in chloride and enriched in the corresponding organic salts. While formation of the organic salts products is not thermodynamically favored for bulk aqueous chemistry, these reactions in aerosol are driven by high volatility and evaporation of the HCl product through large surface area of the particles. This substantial chemical reactivity of sea salt particles with organic acids has been largely overlooked in the atmospheric aerosol chemistry. Atmospheric aging, and in particular hydration‐dehydration cycles of mixed sea salt/organic particles may result in formation of organic salts that will modify the acidity, hygroscopic and optical properties of aged particles.