Johansen, A. M. California Institute of Technology, annaj@cco.caltech.edu
Siefert, R. M. Chesapeake Biological Lab., Univ. MD CES, siefert@cbl.umces.edu
Hoffmann, M. R. California Institute of Technology, mrh@cco.caltech.edu

 
LABILE FERROUS IRON OVER THE TROPICAL ATLANTIC OCEAN
 
Labile ferrous iron (Fe(II)) was measured over the Atlantic Ocean between Barbados and Cape Verde during the spring of 1997 aboard the R/V Seward Johnson. A high volume dichotomous virtual impactor was used to collect two size fractions (Dp50 = 3um) of 24-hr averaged ambient aerosol samples. Besides the immediate colorimetric quantification of labile Fe(II) aboard the ship, samples were also analyzed for 32 elements (ICPMS), and cations and anions (IC) upon return from the cruise. Labile Fe(II) in the coarse fraction accounted for 0.3 to 1.1% (0.3-5.9 ng/m3) of total coarse iron (determined by ICP-MS), while the analogous numbers for fine Fe(II) were 0.6 to 3.7% (1.7-17.2 ng/m3). Although total iron was found almost evenly distributed between fine and coarse fractions, about 75% of all labile Fe(II) was present in the fine fraction. Observations are further discussed in light of other trace metal abundances and air mass back trajectory analyses, and implications are made on the potential effect on biologic activity in surface waters.
 
Day: Wednesday, Feb. 3
Time: 09:00 - 09:15am
Location: Sweeney Center
 
Code: SS50WE0900S