%0 Journal Article
%A Pohlmeier, A.
%A Haber-Pohlmeier, S.
%A Stapf, S.
%T A Fast Field Cycling Nuclear Magnetic Resonance Relaxometry Study of Natural Soils
%J Vadose zone journal
%V 8
%@ 1539-1663
%C Madison, Wis.
%I SSSA
%M PreJuSER-5532
%P 735 - 742
%D 2009
%Z The authors thank the German research fund (DFG) for financial support (Sta 511/4- 1, PO 746/2-1, and Transregio/SFB32), F. Pauly and U. Lesten (ZAT, Research Center Julich) for the recording CT images, C. Walraf (ICG-4, Research Center Julich) for the BET measurements, and J. Koestel and A.-P. Schmidt-Eisenlohr (ICG4, Research Center Julich) 360 for the water retention curves of the soils.
%X This study used nuclear magnetic resonance (NMR) relaxometry at different Larmor frequencies to investigate water dynamics in the pore space of natural porous media. Spin-lattice NMR relaxation times (T-1) were determined in purified fine sand and two natural soils, Kaldenkirchen sandy loam and Merzenhausen silt loam, by means of fast field This technique investigates relaxation processes as a function of the Larmor frequency. in the 0.005 and 20 MHz, yielding so-called relaxation dispersion curves (1/T-1 vs. log.). The data were further by means of inverse Laplace transformation to calculate the T-1 relaxation time distribution functions. Only sand was characterized by monomodal distribution with T-1 of about 1 s at 20 MHz, whereas the natural soil showed multi modal distribution functions in the range between 2 and 70 ms. With decreasing Larmor frequency, all distribution functions kept their shapes but were shifted to faster relaxation times. The corresponding relaxation dispersion curves indicate predominance of two-dimensional diffusion of water in the soils, whereas in the sand, diffusion behaved like unrestricted three-dimensional diffusion. In terms of the Brownstein-Tarr model, in the T-1 relaxation times with increasing silt and clay content can be explained by an increase of the volume ratios (S/V) of these porous media, i.e., by a decrease in the pore sizes. Finally, distribution functions of size parameter V/S were obtained from the spin-lattice relaxation time distributions by normalizing on the specific surface area. They ranged from submicrometers in the Merzenhausen soil to micrometers and submillimeters in soil and fine sand, respectively.
%K J (WoSType)
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000268871900020
%R 10.2136/vzj2008.0030
%U https://juser.fz-juelich.de/record/5532