AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, 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: 433 Working Group: Aerosol Chemistry
Abstract Mineral dust aerosols contain approximately 3% iron by mass and can undergo long range transport resulting in an estimated 14-16 Tg of iron deposited into the oceans annually. Although there is significant iron deposition into the oceans, only a small percentage of it is soluble, and thus bioavailable. In high-nutrient, low chlorophyll ocean regions iron solubility may limit phytoplankton primary productivity. Researchers have examined the atmospheric transport processes iron-bearing particles undergo, but particle size has been overlooked. In this work, the effect of particle size on iron solubility in atmospheric aerosols is examined. Pure iron-containing phases (red hematite, black hematite, magnetite, goethite, illite, kaolinite, and quartz) were separated into five different 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. Particle size was confirmed by scanning electron microscopy (SEM). The extracted mineral solutions were analyzed for soluble iron content by inductively coupled plasma-mass spectrometry (ICP-MS). Fe(II) and Fe(III) content was determined by a ferrozine/UV-VIS method. Preliminary results show low iron solubility (~0-0.3%) for iron oxides (hematite, magnetite, and goethite) and higher solubility (1-35%) for clays (kaolinite and illite) when extracted into an acetate and cloudwater buffers (pH 4.25-4.3). The iron solubility of the iron oxides and clays increases to approximately 0.5-3% and 5-70%, respectively, when extracted into a marine aerosol solution (pH 1.7). When extracted into the acetate and cloudwater buffer there is a trend showing higher iron solubility in the largest and smallest size fractions, with lower iron solubility is the mid-range size fraction (1-0.5 micro-meter). When extracted into the marine aerosol solution there is increased iron solubility with decreasing particle size.