J. Jpn. Soc. Soil Phys. No. +*, p.+++3,**1 **** Soil Temperature Change and Heat of Wetting during Infiltration into Dry soils Takeo AKAE*, Aya TANAKA** and Munehide ISHIGURO* * The Graduate School of Environmental Science, Okayama University, -++ Tsushima-Naka, Okayama, Japan ** Okayama Prefecture Association of Land Improvement Project Promotion, +-1 Uchisange, Okayama, Japan Abstract In infiltratioin process of water to dry soils, rise of the temperature just before the wetting front arrival is observed. This phenomenon is caused by wetting heat released by adsorption of water vapor onto the soil and or wetting of the soil. The temperature change a#ects not only soil water potential, infiltration itself due to change in viscosity of the water but also bio-chemical phenomena by changing temperature environment. However, few quantitative experiments and analytic studies have been made on this phenomena of natural soils, many problems remain to be solved on this matter. In this research, to evaluate the soil temperature change quantitatively, infiltration experiment was conducted on three types of natural soils under thermally insulated condition and the temperature change was monitored. In addition, wetting heat of the soils was measured by calorimetric method. The experimental results showed that the temperature increased at just before the wetting front by,.-,,+. and /.2 for the Masa soil, Ando soil and the red yellow soil, respectively. We observed strong relationship between the increases in the temperature and the wetting heats of each soil. The wetting heats of each soil showed strong relationship with the cation exchange capacity. Key words : Infiltration, Heat of wetting, Specific surface, Adiabatic infiltration experiment, Cation exchange capacity + Keren and Shainberg, +31/, +313, +32* ; Kijne, +33 Iwata, S. et al., +322 +311 Berge, H.F.M. ten, +33 * 1**2/-* - ++ ** 1***2,. +-1 :
12 +*,**1 Anderson and Linville +3, +3- Perrier and Prakash +311 CEC,,+,++ -,+, JIS pf -.//./ Decagon Device Inc., WP-. N, BET,-**, mm CEC,, + / cm,, cm / cm,* cm, cm +* /* cm / cm /* cm Fig. + + Infiltration apparatus under thermoinsulated condition., mm, mm - ++*,. +./* gcm - *.3 gcm - +.,* gcm - EF / cm,,* / cm +,
: 13,-,, mm,* g, ++*,., + - - + EF -,, - Q imc sw stt sc ww wtt ww s Q im : Jg + T : T s : T w : C s : Jg + K + W s : g C w : Jg + K + W w : g *..,/ mm, mm *.*1/ mm *.*1/*..,/ mm, *..,/ *.2/ mm, *.2/,.** mm. - -+ + - - + gcm -,4.,4,,4 *4*,,4* mm *4**,*4*, *4**, mm 1/ +- -+ -.,/ 2/ +, - SL SCL SL -*43,*4, +*41 +412-2 -.4. -4 *4.,24+ +14/ +*4-4/- m, g.4*/ +-42,/42,4+ +.4, +4- cmol ckg.4.. --4+ 2431, - Fig., Wetting heat measurement apparatus. Fig. - Soil moisture characteristic curves of soils.
14 +*,**1 Fig... Temperature change at each depth during infiltration.
: 15 Fig. / / Locations of wetting fronts and maximum temperature.
16 +*,**1 Fig. Temperature profiles at di#erent times during infiltration.
: 17,/.2 m, g, +-.2 m, g..*/ m, g -.++* - cm pf -./ -.++* / cm pf /./ -, -,+. 1 cm, +1 cm,,1./ cm, -1./ cm,.1./ cm -,-,*,/../., -,, / - Anderson +3, -,-,-.1.1./,./ -- --+ -,..2- Jg Iwata, S. et al., +322 /.3 Jg +.+,+.,+.. Jg /.. Jg, -.,/ Jg *, Jg -4,/,+4.* /4..42- *4// -432 +4,, *412 +43 +24,+4 +4+ /43* * : Iwata S. et al. (+322)
18 +*,**1 *.2+. +.*. +.* JgK..*,*..., --, - *.*1/ mm -*.* Jg *.*1/ mm *.*1/*..,/ mm,,. Jg,/ *..,/*.2/ mm,,./ Jg *.2/,.* mm +3.3 Jg,.* mm,+. Jg -. -.. --- 1. / pf.., pf /., pf..,/., --. CEC - 2 +311 N, N, Fig. 1 1 Dependence of wetting heat on initial water content. 2 Fig. 2 Relationship between wetting heat and CEC and that of between wetting heat and specific surface. - Jg mm *4*1/ *4*1/*4.,/ *4.,/*42/ *42/,4* run + run,,341 -*4,,-4-,+43,,43,,4*,*4, +34/ -*4*,,4,,4/ +343
: 19.,.-,+. /.2 CEC Anderson, D.M. and Linville, A. (+3,) : Temperature fluctuations at a wetting front : I. Characteristic temperature-time curves, Soil Sci. Soc. Am. J.,, : +.+2. Anderson, D.M. and Linville, A. (+3-) : Temperature fluctuations at a wetting front : II. The e#ect of initial water content of the medium on the magnitude of the temperature fluctuations, Soil Sci. Soc. Am. J.,,1 : -1-3. Berge, H.F.M. ten : +33 : p. -+. Iwata, S. (+31,) : Thermodynamics of soil water. II, Soil Sci., ++- : -+--+. Iwata, S., Tabuchi, T. and Warkentin, B.P (+322) : Soilwater interaction Machanism and application, Mercel Dekker Inc., New York : p. +*,. Keren, R. and I. Shainberg (+31/) : Water vapor isotherms and heat of immersion of Na- and Ca- Montmorilonite sysytems, I. Homoionic clay, Clays and Clay Minerals,,- : +3-,**. Keren, R. and I. Shainberg (+313) : Water vapor isotherms and heat of immersion of Na- and Ca- Montmorilonite sysytems, II. Mixed systems, Clays and Clay Minerals,,1 : +./+/+. Keren, R. and I. Shainberg (+32*) : Water vapor isotherms and heat of immersion of Na- and Ca- Montmorilonite sysytems, III. Thermodynamics, Clays and Clay Minerals,,2 :,*.,+*. Kijne, J.W. (+33) : On the interaction of water molecules and Montmorilonite surfaces, Soil Sci. Soc., Amer. Proc., -- : /-3/.-. +311 : S.S 2 /*/1. Perrier, E.R. and Prakash, O.M. (+311) : Heat and vapor movement during infiltration into dry soils, Soil Sci., +,. (,) :1-1.,.-,+. /.2 CEC :,**1 +. :,**1. +2