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Determination of photochemically available iron in ambient aerosols

Siefert, Ronald L. and Webb, Samuel M. and Hoffmann, Michael R. (1996) Determination of photochemically available iron in ambient aerosols. Journal of Geophysical Research D, 101 (D9). pp. 14441-14449. ISSN 0148-0227. doi:10.1029/96JD00857.

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Experiments to determine the concentration of photochemically available Fe in ambient aerosol samples were carried out using a novel photochemical extraction procedure. Ambient aerosol samples, which were collected on Teflon filters, were suspended in an aqueous solution within a photochemical reactor and irradiated. Under these conditions, which were favorable to the photochemical weathering of aerosol particles, the relative amount of Fe(II)_(aq) to Fe_(total) was shown to increase. The extent and rate of Fe(II)_(aq) photoproduction was used to characterize the Fe in aerosol samples collected from Whiteface Mountain, New York, Pasadena, California, San Nicholas Island, California, and Yosemite National Park, California. Photochemically available Fe concentrations found ranged from <4 ng m^(−3) (0.07 nmole m^(−3)) to 308 ng m^(−3) (5.52 nmole m^(−3)), Fe_(total) concentrations ranged from 10 ng m^(−3) (0.18 nmole m^(−3)) to 3400 ng m^(−3) (61 nmole m^(−3)), and the percentage of photochemically available Fe to Fe_(total) ranged from 2.8% to 100%. Aerosol samples were also collected during biomass burning events in southern California; these samples showed insignificant changes in the photochemically available Fe (compared to nonbiomass burning samples) in conjunction with large increases of Fe_(total). Calculations based on these experiments also provide further evidence that redox reactions of Fe in cloudwater could be an important in situ source of oxidants (OH, HO_2/O_2^−). The estimated oxidant production rate in cloudwater based on these experiments is between 0 and 60 nM s^(−1), with an average value of 16 nM s^(−1). This estimated in situ oxidant production rate due to Fe chemistry is approximately equal to previous estimates of the oxidant flux to cloudwater from the gas phase.

Item Type:Article
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Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 1996 American Geophysical Union. Received July 20, 1995; revised January 5, 1996; Accepted February 27, 1996. Special thanks are extended to Anne Foster and Richard MacDonald of the ASRC at Whiteface Mountain, Andy Friedland at Dartmouth College, Diane Ewell and Annie Esperanza of Sequoia National Park, and Jan van Wagtendonk at Yosemite National Park for their help. We also thank J. J. Morgan of Caltech for helpful discussions. Support for this research has been provided by a grant from the National Science Foundation, Division of Atmospheric Sciences, Atmospheric Chemistry Section (ATM 9015775; ATM 9303024). This research was also sponsored by the U.S. Department of Energy, Office of Energy Research, Environmental Sciences Division, Office of Health and Environmental Research, under appointment to the Graduate Fellowships for Global Change administered by Oak Ridge Institute for Science and Education.
Funding AgencyGrant Number
NSFATM 9015775
NSFATM 9303024
Department of Energy (DOE)UNSPECIFIED
Issue or Number:D9
Record Number:CaltechAUTHORS:20150810-152944726
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Official Citation:Siefert, R. L., S. M. Webb, and M. R. Hoffmann (1996), Determination of photochemically available iron in ambient aerosols, J. Geophys. Res., 101(D9), 14441–14449, doi:10.1029/96JD00857
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59363
Deposited By: Ruth Sustaita
Deposited On:11 Aug 2015 17:51
Last Modified:10 Nov 2021 22:19

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