Photoelectric charging experiments measure the uptake kinetics of pyrene gas onto model sea spray aerosol particles.  The particles consist of a 200-nm core of NaCl coated with a variable thickness of either oleic or myristic acid.   Tandem differential mobility analysis characterizes the coating thickness to within 0.5 nm.  The coated particles interact with pyrene gas in a sliding injector flowtube, and a laser-based photoelectric charging experiment measures the concentration of surface-adsorbed pyrene.  A multilayer kinetic model, which includes separate rate constants for adsorption onto and desorption from bare NaCl surface, organic-coated surface, and pyrene-coated surface, models the concentration as a function of interaction time.  The results show that the oleic acid spreads into a uniform layer, while the myristic acid clumps up, leaving as much as 40% of the surface uncovered when the nominal particle diameter increases by 10%. For both oleic and myristic acid, the uptake of pyrene is slower on the partially organic-coated particles by approximately a factor of two.  In the limiting case of 100% organic coverage, however, the net uptake of pyrene onto oleic acid coating is significantly greater than the net uptake onto myristic acid.  Lastly, rapid desorption from the organic-coated surface limits the steady state concentration of adsorbed pyrene, mitigating the health risk associated with the inhalation of particle-bound PAH.

Uptake of pyrene by model sea spray aerosol particles

247th National Meeting (2014)

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