| Observations of magnetite dissolution in
poorly drained soils |
|
| Author(s): Grimley
DA (Grimley, David A.), Arruda
NK (Arruda, Nancy K.) |
| Source:
SOIL SCIENCE Volume:
172 Issue:
12 Pages:
968-982 Published:
DEC 2007 |
| Times Cited:
0 References:
46 |
| Abstract:
Dissolution of strongly magnetic minerals is a common and relatively
rapid phenomenon in poorly drained soils of the central United States,
resulting in low magnetic susceptibility (MS). Low Eh reducing
conditions are primarily responsible for magnetic mineral dissolution;
a process likely mediated by iron-reducing bacteria in the presence of
soil organic matter. Based on transects across drainage sequences from
nine sites, natural magnetic minerals (>5 mu m) extracted from
surface soil consist of 54% +/- 18% magnetite, 21% +/- 11%
titanomagnetite, and 17% +/- 14% ilmenite. Magnetite and
titanomagnetite dissolution, assessed by scanning electron microscopy
on a 0-to-3 scale, inversely correlates with surface soil MS (r(2) =
0.53), a proxy for soil drainage at studied transects. Altered
magnetite typically displays etch pits <1-mu m diameter, whereas
titanomagnetite exhibits a latticework pattern of alteration along
planes of crystallographic weakness (<1-mu m spacing). Ilmenite,
containing solely ferrous iron, is unaffected by reducing conditions,
portraying mainly smooth-textured grains. Magnetic fractions (>5 pm)
include 26% +/- 18% anthropogenic fly ash that also exhibits greater
dissolution in low MS soils (r(2) = 0.38), indicating detectable
alteration can occur within 150 years in low Eh soils. Laboratory
induced reduction of magnetite, titanomagnetite, and magnetic fly ash,
with a citrate-bicarbonate-dithionite solution, resulted in dissolution
textures similar to those of in situ soil particles. Although
experiments indicate that reductive dissolution of magnetite can occur
abiotically under extreme conditions, bacteria likely play an important
role in the natural environment. |
| Document Type:
Article |
| Language:
English |
| Author Keywords:
magnetite; ilmenite; dissolution; fly ash; scanning electron microscopy
|
| KeyWords Plus:
FINE-GRAINED MAGNETITE; HYDRIC SOILS; POWER-PLANT; SUSCEPTIBILITY;
SEDIMENTS; EROSION; MORPHOLOGY; MAGHEMITE; FELDSPAR; MINERALS |
Addresses:
Grimley, DA (reprint author), Illinois State Geol Survey, 615 E Peabody
Dr, Champaign, IL 61820 USA
Illinois State Geol Survey, Champaign, IL 61820 USA |
| E-mail Addresses:
dgrimley@uiuc.edu |
| Publisher:
LIPPINCOTT WILLIAMS & WILKINS, 530 WALNUT ST, PHILADELPHIA, PA
19106-3621 USA |
| Subject Category:
Soil Science |
| IDS Number:
241ZU |
| ISSN:
0038-075X |
| DOI:
10.1097/ss.0b013e3181586b77 |