J. Jpn. Soc. Soil Phys. No. +*+, p.,1 -/,**/ * ** * Development of Automated Suction Controlled Flux Sampler for Unsaturated Sandy Soil Naoko HIGASHI*, Yasushi MORI** and Mitsuhiro INOUE* * Arid Land Research Center, Tottori University, +-3* Hamasaka, Tottori 02* ***+, Japan ** Faculty of Life and Environmental Science, Shimane University, +*0* Nishikawatsu, Matsue 03* 2/*., Japan Abstract A sandy field has the potential hazard of nitrate contamination because of its low fertilizer holding capacity. A suction controlled flux sampler (SCFS) consisting of an automated vacuum system and a sampling filter device has been developed for accurate measurement of water flux from the root zone. Knowing that water content in sandy field was highly sensitive to suction change, a bu#er container was placed between the pump and a sampling bottle to apply moderate suction and avoid accidental over-sucking. A sampling device with a glass filter was placed in a dune sand column and infiltration experiments were conducted. A moderate suction was achieved and the resulting water-collecting e$ciency was from 3. to +*3 under continuous rainfall. It showed that SCFS collected infiltrated water e#ectively without disturbing the infiltration streamline. Key words : dune sand, suction control, unsaturated soil, water-collecting e$ciency. + +32,,***,**, +33- +332,**-,**+ * 02* ***+ +-3* ** 03* 2/*. +*0* :
28 +*+,**/,**.,***,**, van Grinsven et al. +322 +*,***,, +,., -. + Suction Controlled Flux Sampler ; SCFS + van Grinsven et al. +322 Inoue and Dirksen,*** SCFS Sampling Filter Device ; SFD Automated Vacuum System ; AVS + SFD + SCFS Fig. + Schematic of the suction controlled flux sampler (SCFS).
: 29,**- ;,**. + SFD AVS. cm,./ cm + h C h L, h R - h C h LR AVS SFD. EC EC AVS CR+*X ; Campbell Scientific / + V - 2* cm h C h LR / cm -. +. + h C h LR / cm AVS h C h LR / cm V + +*,,,, +, HYDRUS-,D ver.,.*/ ;S imu nek et al., +333 ;,**. SCFS /* cm,* cm. cm /* cm /* cm HYDRUS-,D van Genuchten-Mualem Model : q r *.*.20 q s *..+-, a *.*- cm + n /./ K s 10*..2 cm d + l *./ : q r *.*,2- q s *.-- a *.*+ cm + n /.* K s /*.31 cm d + l *./ h C h LR / cm V, +* + Table + Specification of the glass filter Filter No. G. Diameter (cm) Thickness (cm) Pore size (mm) Air entry value (cm) Saturated hydraulic conductivity (cm s + ) +* *42 / +* 3* +-*, /42 *4- +*. Fig., Water retention curve of the Tottori dune sand.
30 +*+,**/ +,* mm h + +,,,, Kosugi and Katsuyama,,**.,**- + -,/** cm - +/ -** cm 2* cm, * 2* cm 2* cm 2* -** cm -** cm 2* cm -** cm 0-* +,/** -,/**.,-** 0,0** cm - 2* -** cm +*, - -,* cm +*/ cm PVC *.2/ mm +.// Mg m - +*/ cm 1* cm 1* cm - /* cm q s Fig. - Schematic ofthe soil column experimental set up. Upper part ofthe column indicates the area ofthe q s for WCE estimation. SFD /* cm -.1./ cm TDR +.2 cm 0 cm - :,* -*.*.0 1* cm UNSUC :,* -*.* 1* cm + +/ cm q i, +* mm h + Run-+ q i, mm h + SCFS AVS +/ cm Run-, Run-- q i, mm h + +* mm h + AVS SCFS
: 31 /* cm,. SCFS Water-Collecting Efficiency ; WCE Run +Run +, Q r cm - Run q r cm h + SCFS Q e cm - Run q e cm h + TDR * /* cm - q s cm h + q s SCFS WCE WCE +** q e q r q s (+) WCE +** SFD +** SFD Q d cm - Change of Water Storage in the column ; CWS CWS +** CWS +** CWS +** Q e Q d Q r (,) - - + - + + h C h LR *./ cm Inoue and Dirksen,,*** h C h LR,*** h C h LR * HYDRUS-,D. a h C h LR h C h LR *. b. c. a h C h LR,./ cm,* mm h + h C h LR * cm h C h LR / cm h C h LR / cm - +, 1** cm -,/** cm - +/ 2* -** cm / -** cm 2* cm -** cm 2* cm, /* cm 2* cm /* cm / 0-* +,/** cm - +,/** cm - +* - + - AVS
32 +*+,**/ Fig... HYDRUS-,D /* cm a : SFD b: c:,* mm h + Results of the calculation by HYDRUS-,D with /* cm constant suction at the filter. a : Changes of the matric potential inside and outside of the SFD. b : Soil water content under free drainage. c : Soil water content under continuousrainfall with,* mm h -+ / 2* cm -** cm +* Fig. / Maximum suction in di#erent sampling bottlesconnected with the bu#er container. 0 Flag, ON Count,.** + *./ V + Count+ ++/ +-/ +* V, +* V - 0 Count+,**,-* +/ AVS 2* -** cm +,/** cm - +* - AVS -, SCFS SCFS 1 WCE, Run-+ q i, mm h +
: 33 Fig. 0 0 AVS Time schedule for the suction control by the AVS. 1 Fig. 1 SCFS a: b: c: Infiltration water sampling by SCFS under continuous rainfall. a : Matric potential for suction control. b : Sampling intensity and cumulative amount of sampled water. c : Suction in the sampling bottle and the bu#er container. * /* cm q *.-- *.*- m - m - CWS ++. h C h LR 1 + a WCE /0./, WCE AVS Run-, CWS +++ * /* cm q *.+3 *.*, m - m - WCE 3-.0
34 +*+,**/, Table, SCFS Water-collectinge$ciency under various rainfall conditions Run +, - q i (mm h + ),, +* Q r (cm - ) Q d (cm - ) 1/-40 10*40 1/-40 0/,41-1024*,,-142 Q e (cm - ) 314/ +2-41 +*-+4* CWS ( ) q s (cm h + ) q r (cm h + ) q e (cm h + ) ++-43 *4*+1 *4, *4+*. +++ *4**2 *4, *4+3/ 2042 *4**2 +4* +4*3. Standard deviation (mm h + )* --- *413,4*1 WCE ( ) /04/ 3-40 +*24/ * Standard deviation of samplingintensity (mm h + ) under steady state condition., Run-, Run-+ WCE AVS Run-, WCE +** h C h L h R / cm 1, a, mm h + *. mm h + 1, b AVS -/ cm 1, c Run-- * /* cm q *.,, *.*, m - m - AVS,1 cm 1 - c WCE Run-- +*2./, Run-- Run-, WCE +** +* mm h + * +/ mm h + 1 - b Run-- CWS +**, +*/ cm Run-, - +** AVS Run-+ 1 + b Run-, - 1, b 1 - b Run-, Run-- TDR * /* cm, Run-, Run-- h C 1, a 1 - a Run-, - AVS. h C h LR / cm SCFS 3. +*3 SCFS SCFS +333,*** C. Dirksen B;+0-2*+/3,+ COE
: 35,**, : p.,- pp..,..,**- : // 0, 0-.,**. : +0-10 -11. Inoue, M. and Dirksen, C. (,***) : An Automatically operated soil water flux meter of improved design +, 0-0 0-2. +332 : pp. 32 33,*** : +- 0 :.0,.1+. Kosugi, K. and Katsuyama, M. (,**.) : Controlledsuction period lysimeter for measuring vertical water flux and convective chemical fluxes. Soil Sci. Soc. Am. J.,02 : -1+ -2,. +33- :.*, : 11 2*.,**- : - /-0 :, 3.,**- : +/ --. --/.,**+ : pp. /* /1,*** : p.,/ pp. 00 2, S imu nek, J., Sejna, M. and van Genuchten, M. Th. (+333) : The HYDRUS-,D software package for simulating the two-dimensional movement of water, heat, and multiple solutes in variablysaturated media. Version,.*. IGWMC-TPS-/-, International Ground Water Modeling Center, Colorado School of Mines, Golden, Colorado.,**. : 1/ + :./ /,.,**. : Modelling variably saturated flow with HYDRUS-,D Japanese translation HYDRUS-,D pp. +.+ +./- HYDRUS van Grinsven, J. J.M., Booltink, H.W.G., Dirksen, C., van Breemen, N., Bongers, N. and Waringa, N. (+322) : Automated in situ measurement of unsaturated soil water flux.soil Sci. Soc. Am. J., /, : +,+/ +,+2. 3. +*3 :,**/,,2 :,**/ 1 +,