Sulfuric Acid in the Woods and a Connection to Aerosols

Aerosols are particles in the atmosphere that are responsible for many chemical reactions and play a key role in light reflection. However, even thought aerosols are well known, the formation of aerosols is still unclear. The Chemical Emission, Loss, Transformation and Interactions within Canopies second campaign (CELTIC-II) is looking at the different factors that goes into the makeup of aerosols. One of the key focuses of this study is to look at the concentration of sulfuric acid and OH because of their involvement in aerosol formation. Sulfuric acid is one of the key components to aerosol formation. Because of its low vapor pressure, sulfuric acid in the gas phase rapidly condenses to form particles. Any gaseous sulfate that is found in the atmosphere must have been formed recently by chemical reactions. OH is the atmosphere's primary oxidant and plays many roles in the chemistry of the environment: one being a necessary chemical for sulfuric acid formation in the gas phase. This study looks at concentration of sulfuric acid and OH in the atmosphere at Niwot Ridge Colorado for 4 weeks during the summer of 2006 using a Selected Ion Chemical Ionization Mass Spectrometry (SICIMS), a technique that is able to measure as low as 30-40 ppqv. During days of high sun, SICIMS measured concentrations of Sulfuric acid from 5x106 to 25x106 molecule cm-3 and concentrations of OH around 0.6x106 molecule cm-3. These data will be used in a test model of aerosol formation.