Aerosols affect climate via a complex array of interactions, absorb and reflect solar radiation, serve as cloud condensation nuclei and alter precipitation patterns and global fresh water supply. Aerosol surfaces also control chemical constituents of the atmosphere by providing reactive sites for new chemical reactions. According to the Intergovernmental Panel on Climate Change, the global warming caused by green house gases (+2.5 W/m2) is partially offset by the aerosol (-1.3 W/m2) cooling from reflection thus mitigating current warming influence to one half. Understanding chemical transformations on aerosol surfaces is key to total evaluation of their impact on climate change and projection of global warming due to anthropogenic pollutants. Fine and coarse aerosol samples were collected on filter papers in La Jolla, CA for one week. Back trajectory analysis were performed using the Hysplit model and National Oceanic and Atmospheric Administration (NOAA) meteorological data (http://www.noaa.gov/) to identify the source and transport history of the air masses sampled at La Jolla. Hydrogen peroxide (H2O2) and carbonate formed on aerosol surfaces were quantified and their O-triple isotopic composition was measured to identify the source of oxygen atom acquired during chemical transformation and transport of air masses to the sampling site. Laboratory experiments indicate that the oxygen triple isotopic composition of peroxide depends on the pH of the solution and type of aerosol surface involved. Peroxide formed on aerosols surfaces in the presence of ozone contributes ~ 10% of heterogeneous chemical transformation of S(IV) to S(VI). The mechanism of peroxide formation on various aerosol surfaces at acidic and basic pH will be discussed.

Chemical transformation on aerosol surfaces: Hydrogen peroxide as a new surface player in determining the chemical composition of the atmosphere

243rd National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.