Collaborative Research: Sediment Nanomagnetism and Environmental Change: The Microbial Mineral Link

Project Information

Principal Investigator	Kenneth Nealson
Institution	University of Southern California
Project URL	View
Relevance to Implications	Marginal
Class of Nanomaterial	Natural Nanomaterials
Impact Sector	Environment
Broad Research Categories	Generation, Dispersion, Transformation etc. Characterization
NNI identifier

Funding Information

Country	USA
Anticipated Total Funding	$104,095.00
Annual Funding	$26,023.75
Funding Source	NSF
Funding Mechanism	Extramural
Funding Sector	Government
Start Year	2003
Anticipated End Year	2007

Abstract/Summary

Mineralogical and chemical signatures of environmental change, left behind in the earth’s sediment archives, provide immensely valuable baseline records against which current and future global change an be successfully recognized. Conversion of these qualitative measures to quantitative numerical values of past temperatures and rainfall is the next major challenge in global environmental change research. One successful but qualitative approach has been to observe changes in environmentally sensitive iron oxyhydroxide microcrystals utilizing transmission electron microscopy (TEM), electron emission loss spectroscopy (EELS) and synchrotron x-ray analysis, e.g., extended absorption fine structure (EXAFS). However, it has proven difficult to relate these results from 1-100 nm-sized individual nanocrystals to 100 - 200 mg aliquots of natural sediments. We show that a multi-proxy approach involving whole sample magnetic and Mossbauer effect measurements at low temperatures (4.5K - 300K) and high magnetic fields (3-5 Tesla), combined with TEM/EELS/EXAFS studies of synthesized nanoparticles of goethite, can lead to more precise calibrations for temperature and Eh/pH of the mineral formation environment. We will expand our research into ferrihydrite, nanohematite and nanomagnetite. In particular, dissimilatory iron reducing bacteria (DIRB) will be identified from field experiments on soil profiles and also used as cultured bacteria in in vitro experiments to determine how past temperature, rainfall, and also the length of summer growing season can be obtained from magnetically estimated nanomagnetite in modern soils and ancient soils (paleosols). Our research, it is hoped, will lead to the first controlled experiments on the role of microbes (DIRB) in nanomagnetite mineralization, and a search for iron isotope signatures in microbial nanomagnetite in soils.