AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Aerosol Formation from Hydroxyl Radical Oxidation of Agricultural Amines and Reduced Sulfur Compounds
PAUL VAN ROOY, Kathleen Purvis-Roberts, Philip Silva, David R. Cocker III, University of California, Riverside
Abstract Number: 357 Working Group: Aerosol Chemistry
Abstract Reduced sulfur compounds, from animal waste products, and amines, from cattle exhalation and rumination, are often co-emitted on agricultural land. Reduced sulfur compounds are thought to be important to new particle formation over the oceans. Amines are thought to play an important role in new particle formation around agricultural land. While both of these compound families have been recognized individually, there have been no studies focused on how these agricultural emissions interact to form particles. To begin filling this information gap, experiments were conducted using a 37.5 m3 Teflon chamber housed within the Atmospheric Processes Laboratory at UC Riverside. 100 ppb of a reduced sulfur compound (dimethylsulfide, dimethyldisulfide, methanethiol, or hydrogen sulfide) was injected into the chamber, followed by 100 ppb of an amine (trimethylamine, diethylamine, butylamine, putrescine, ethylenediamine, cadaverine, or ammonia), and finally 1 ppm of hydroxyl radical to push photooxidation. A suite of real time gas-phase and particle-phase instruments measured chemical composition and physical properties of the aerosol. The aerosol yields were substantial and varied depending on the combination of precursors injected. For example, when trimethylamine was injected with dimethylsulfide over 250 μg/m3 of aerosol formed, while trimethylamine with dimethyldisulfide formed around 150 μg/m3. Over 900 μg/m3 of aerosol formed when injecting putrescine with dimethyldisulfide. The presence of humidity had a profound impact on aerosol yield. In some experiments, (trimethylamine with dimethyldisulfide) humidity increased aerosol yield, while in others (ethylenediamine with dimethyldisulfide) aerosol formation was suppressed. Data acquired from the HR-TOF-AMS showed that the composition of the aerosol varied depending on the amine and reduced sulfur tested. Oxidation of dimethyldisulfide with an amine tended to form a larger fraction of sulfate aerosol (30-40%), while oxidation of other reduced sulfur compounds with an amine formed on average only 1-10% sulfate aerosol. Aerosol mass spectra of the individual precursor experiments were compared to that of the interaction experiments. There are several mass-to-charge peaks present in the interaction experiments that are not present in the individual precursor experiments. This novel investigation provides much needed insight into agricultural aerosol formation.