1H and 19F nuclear magnetic resonance microimaging of water and chemical distribution in soil columns.
Nuclear magnetic resonance (NMR) microimaging is a noninvasive and nondestructive technique that has great potential for the study of soil processes. Hydrogen-1 NMR microimaging techniques were used to examine the distribution of water in four different soil cores. Fluorine-19 NMR microimaging is also used to study the transport of three model contaminants (hexafluorobenzene, sodium fluoride, and trifluralin) in soil columns. The 1H water distribution studies demonstrate that NMR microimaging can provide unique detail regarding the nature and location of water in soils. Image distortion (magnetic susceptibility) was observed for soil samples low in water (20-28% by weight) and that contained an iron content of 0.73 to 0.99%. Highly resolved images were obtained for the organic-rich soil (Croatan sample) and also facilitated the analysis of bound and unbound soil water through varying spin echo times. The contaminant studies with 19F NMR demonstrated that preferential flow processes can be observed in soil cores in as little as 16 h. Studies with hexafluorobenzene produced the highest quality images whereas the definition decreased over time with both trifluralin and sodium fluoride as the compounds penetrated the soil. Nonetheless, both 1H and 19F NMR microimaging techniques demonstrate great promise for studying soil processes.
Simpson
Myrna J
MJ
Department of Physical and Environmental Sciences, University of Toronto, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada. myrna.simpson@utoronto.ca
Simpson
André J
AJ
Gross
Dieter
D
Spraul
Manfred
M
Kingery
William L
WL
D005461:Fluorine; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons; D012987:Soil / Q000032:analysis*; D014867:Water / Q000737:chemistry*
D011522:Protons; D012987:Soil; D014867:Water; D005461:Fluorine