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Hydration Kinetics of Wettable and Water-Repellent Soils

Inst. of Science Organic and Environmental Chemistry, Universtiy Koblenz-Landau Universitaetsstr.1, D-56072 Koblenz, Germany

View larger version (23K): [in this window] [in a new window]   Fig. 1. Use of the different subsamples for the experiments performed in this study (WC: water content, x 2: replication with two samples). All moistened samples were derived from the field-moist samples.

View larger version (35K): [in this window] [in a new window]   Fig. 2. Water uptake of the air-dried Samples T1 and T2 and their organic-free references (two replications for each sample). Shortly after starting the experiment, the water contents of all samples that were moistened via the liquid phase proceeded above the axis break, while the water contents of all samples that were moistened via the gas phase remained below the axis break.

View larger version (46K): [in this window] [in a new window]   Fig. 3. Freezing and melting process (left) and water evaporation (right) of T1 after moistening to water contents of 30.2% (top) and 55.0% (middle) and of T2 after moistening to a water content of 55.0% (bottom). In all graphs, the field-moist T1 and T2 samples are included for comparison. The arrow pointing to the evaporation curve of the field-moist T1 sample indicates an additional evaporation peak.

View larger version (26K): [in this window] [in a new window]   Fig. 4. Thermogravimetry of the air-dried Samples T1 and T2. The arrow pointing to the thermogram of the T1 sample indicates an additional peak at 133 ± 1°C.

View larger version (27K): [in this window] [in a new window]   Fig. 5. Freezing and melting enthalpies (related to wet sample mass) of field-moist samples from the locations Tiergarten and Buch (Hurrass and Schaumann, 2006; Täumer et al., 2005) as a function of the water content (related to wet sample mass). Additionally, the moistened T1 and T2 samples are included in the graph (15 min, 2 d, 7 d, and 21 d after moistening). All field-moist water-repellent samples are circled. The linear regressions were performed only for the field-moist samples.

View larger version (17K): [in this window] [in a new window]   Fig. 6. Specific freezing enthalpies of the moistened Samples T1 and T2 during the course of hydration, of the field-moist samples T1 and T2, and of a quartz sand–water mixture (19.0% water content related to dry sample mass). The errors were calculated on the basis of the difference between the measurement replications.

View larger version (50K): [in this window] [in a new window]   Fig. 7. Comparison of the amounts of unfreezable water and of water in Pore Type I (Schaumann et al., 2005) during the course of hydration for the water-repellent samples T1 and T3 and the wettable Samples T2 and T4 after moistening them to 54 or 55% for the nuclear magnetic resonance and the differential scanning calorimetry measurements, respectively. The errors were calculated on the basis of the difference between the measurement replications.