AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
The Effect of Particle Size on Iron Solubility in Atmospheric Aerosols
AURELIE MARCOTTE, Brian Majestic, Ariel Anbar, Pierre Herckes, Arizona State University
Abstract Number: 547 Working Group: Aerosol Chemistry
Abstract The long range transport of mineral dust aerosols, which contain approximately 3% iron by mass, results in an estimated 14-16 Tg of iron deposited into the oceans annually; however, only a small percentage of the deposited iron is soluble. In high-nutrient, low chlorophyll ocean regions iron solubility may limit phytoplankton primary productivity. Although the atmospheric transport processes of mineral dust aerosols have been studied, the role of particle size has been given little attention. In this work, the effect of particle size on iron solubility in atmospheric aerosols is examined. Iron-containing minerals (illite, kaolinite, magnetite, goethite, red hematite, black hematite, and quartz) were separated into five size fractions (10-2.5, 2.5-1, 1-0.5, 0.5-0.25, and <0.25 micro-meter) and extracted into buffer solutions simulating environments in the transport of aerosol particles. Preliminary results show that differences in solution composition are more important than differences in size. When extracted into acetate and cloudwater buffers (pH 4.25-4.3), < 0.3% of the Fe in iron oxides (hematite, magnetite, and goethite) is transferred to solution as compared to ~0.1-35% for clays (kaolinite and illite). When extracted into a marine aerosol solution (pH 1.7), the percentage of Fe of the iron oxides and clays transferred to solution increases to approximately 0.5-3% and 5-70%, respectively. However, there is a trend of increased %Fe in the minerals transferred to solution in the largest and smallest size fractions, and decreased %Fe in the minerals transferred to solution in the mid-range size fraction when extracted into the acetate and cloudwater buffers. When extracted into the marine aerosol solution the %Fe in the minerals transferred to solution increases with decreasing particle size. By examining the role of particle size, this work will provide a more complete understanding of iron dissolution during atmospheric transport of mineral dust aerosols.