AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Measurements of Organic Acids in Eastern U.S. Radiation Fogs
DEREK STRAUB, Susquehanna University
Abstract Number: 289 Working Group: Aerosol Chemistry
Abstract Measurements of fog chemical composition have been ongoing at a rural site in central Pennsylvania since 2007. These measurements have focused on the analysis of inorganic ion concentrations and the compilation of a long-term record of fog composition in this region. Starting in 2012, organic acids were added to the analysis protocol. Of the 78 total fog samples collected through the end of 2012, 62 samples have been analyzed for major inorganic ions and 21 samples for organic acids.
Fog samples were collected with an automated Caltech Heated Rod Cloudwater Collector (CHRCC) operated on the campus of Susquehanna University, a setting influenced by local agricultural emissions and transport from the industrial Midwest. The collection system was activated when visibility dropped below 500 m and a single bulk sample was collected during each fog episode. Sample volumes averaged 30 ml and the volume weighted average pH was 4.9.
While ammonium and sulfate were the most abundant ions in the fog samples, organic acids were found to contribute significantly to total ion loading. On average, organic acids accounted for 41% of anions in solution. Formate was the third most abundant ion observed, followed by calcium, nitrate, and acetate. The average formate to acetate ratio was 3.3:1. Propionate and oxalate were also present in the fog samples but at lower concentrations. Seven additional organic acids were measured, but concentrations of these were often, but not always, below detection limits. Results from the fog sampling campaign will be presented along with comparisons to organic acid measurements for dew samples that had higher pH values but lower total ion concentrations.