Inhaltszusammenfassung

1H NMR relaxometry has been used to analyze pore size distributions of wet porous samples. To make this method applicable to soil samples, the knowledge about contribution from the soil solution to the total proton relaxation is needed. We extracted soil solutions from 9 soil samples and determined transverse proton relaxation rates, concentration of Fe, Mn, TOC and the pH in the solutions. The effects of Fe, Mn, TOC on the proton relaxation in soil so...1H NMR relaxometry has been used to analyze pore size distributions of wet porous samples. To make this method applicable to soil samples, the knowledge about contribution from the soil solution to the total proton relaxation is needed. We extracted soil solutions from 9 soil samples and determined transverse proton relaxation rates, concentration of Fe, Mn, TOC and the pH in the solutions. The effects of Fe, Mn, TOC on the proton relaxation in soil solution were compared to those of dissolved Fe2+, Fe3+ and Mn2+ and of glucose, D-cellobiose, potassium hydrogenphthalate, sodium alginate and agar in model solutions. Proton relaxation rates in the soil solutions were up to 20 times larger than in pure water, which was mainly due to dissolved Fe(III) and Mn(II) species. The relaxivities of Fe and Mn in soil solution were reduced to 40 and Mn(II) in model solution, respectively. Smaller relaxivities were primarily due to formation of metal- organic complexes. We conclude that the proton relaxation in soil samples is generally accelerated by the soil solution, and its contribution must be considered to estimate pore sizes from relaxation times. By using the calculated relaxivities of Fe and Mn in soil solution, the contribution of the soil solution to the total proton relaxation can be estimated from the Fe and Mn concentration in soil solution.» weiterlesen» einklappen

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