AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
The Effects of Particle Size, Relative Humidity, and Sulfur Dioxide on Iron Solubility in Atmospheric Particulate Matter
BENTON CARTLEDGE, Brian Majestic, Aurelie Marcotte, Pierre Herckes, Ariel Anbar, University of Denver
Abstract Number: 396 Working Group: Aerosol Chemistry
Abstract Iron is the most abundant transition metal in atmospheric particulate matter (PM). Iron also plays a critical role in the atmospheric sulfur and carbon cycles; however, the extent of that role is believed to be dependent on iron solubility. Changes in iron solubility can also affect numerous other processes such as ocean fertilization and the redox activity of inhaled PM$_(2.5). Increased redox activity of iron in inhaled PM$_(2.5) has been linked to increased occurrences of cancers, asthma, and other cardiovascular/pulmonary diseases. Particulate iron can be transported thousands of kilometers from its source interacting with other atmospheric species such as short chain organic acids, ammonium nitrate, and anthropogenic species such as SO$_2. During transport and interactions with these species in an aqueous environment, the probability of chemical reaction increases which could contribute to iron solubilization. The current study focuses on studying the effects of particle size, relative humidity, and exposure to SO$_2 on iron solubility. To mimic oceanic particles, iron minerals were resuspended with sodium chloride and size-segregated on Teflon filters using a Sioutas personal cascade impactor sampler (PCIS). These samplers were then exposed to SO$_2 at marine environment humidity (>80%) and arid environment humidity (24%). Soluble iron was determined by extracting the samples in a buffer and then analyzing the extracts via inductively-coupled plasma mass spectrometry (ICP-MS). Total iron was measured by digesting the samples in strong acid using a microwave digestion system and analysis via ICP-MS. As particle size decreased, percent solubility was shown to increase. Additionally, increased iron solubility was linked to increased relative humidity and exposure to SO$_2. Since a large amount of atmospheric dust originates in desert regions, gas-particle phase interactions with urban gasses (SO$_2) appear to be an important factor in increasing iron solubility especially as the particle is transported into a more aqueous environment.