Abstract

To understand wintertime controls of biogeochemical processes in high latitude soils it is essential to distinguish between direct temperature effects and the effects of changes in water availability mediated by freezing. Efforts to separate these controls are hampered by a lack of adequate methods to determine the proportion of unfrozen water. In this study we present a high-field (H2O)-H-2 NMR method for quantifying unfrozen water content in frozen soil. The experimental material consisted of the humic layer of a boreal spruce forest soil mixed with varying proportions of quartz sand and humidified with deuterium-enriched water. The relative standard deviation of unfrozen water content (measured as NMR signal integral) was less than 2% for repeated measurements on a given sample and 3.5% among all samples, based on a total of 16 measurements. As compared to H-1 NMR, this H-2 NMR method was found to be superior for several reasons: it is less sensitive to field inhomogeneity and paramagnetic impurities, it gives a bigger line shape difference between the ice and liquid signal, it shows a sharper response to water fusion, and it excludes the possibility of hydrogen in the organic material interfering with the measurement

Published in

Environmental Science and Technology
2004, Volume: 38, number: 20, pages: 5420-5425
Publisher: AMER CHEMICAL SOC

SLU Authors

• Nilsson, Mats

  • Department of Forest Ecology, Swedish University of Agricultural Sciences
    

• Öquist, Mats

  • Department of Forest Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Environmental Sciences related to Agriculture and Land-use


Publication identifier

DOI: https://doi.org/10.1021/es0193695

Permanent link to this page (URI)

https://res.slu.se/id/publ/3418