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J. Jpn. Soc. Soil Phys.

No. +*3, p. -+. ,**2

¬­ *ῌT ®¯*ῌ°±¨²*ῌ³´*ῌTµ¬**Soil Environment Monitoring by Multi-frequency Electromagnetic Sounding
Yuuya HIRAI*, Yasushi MORI*, Hiroaki SOMURA*, Naokazu EGUSA* and Taihei MORISAWA*** Faculty of Life and Environmental Science, Shimane University,+*0* Nishikawatsu, Matsue 03*ῌ2/*., Japan** The United Graduate School of Agricultural Sciences, Tottori University,.ῌ+*+ koyama-minami, Tottori 02*ῌ2//-, Japan
Abstract
Surface soil environment was surveyed and characterized using a multi-frequency electromagnetic wave (EM) sensor.

Traditional resistivity method needs multiple point electrodes in theﬁeld to investigate the deeper points, however, this method uses broadband electromagnetic data
to obtain the apparent conductivity from di#erent depth, i.e., the higher the frequency, theshallower data we can obtain. It is non-invasive and rapid, therefore, appropriate for wide area
environmental survey.

Five frequencies of ,-+*, -21*, 13/*, ,./+* and .131* Hz were applied sothat we obtained vertical proﬁle of the domain. Forest under di#erent management, winterponded paddy ﬁeld, orchard and tea farm in hilly mountainside and orchard in plain ﬁeld were
investigated using a broadband electromagnetic wave sensor sounding.

Surface electrical con-ductivity (EC) obtained by Wenner array has the highest correlation with .131*Hz data, showing
it is the appropriate frequency for surface soil investigation. Moreover, EC in the order of several
tens milli-Siemens obtained by EM sounding corresponded very well with the EC obtained bytraditional method. Conductivity data successfully showed management induced changes insoil environment by conductivity map along with vertical conductivity proﬁle, which is advantage of broadband EM survey.

Water content changes in forest after rainfall, e#ect of ponding

management in paddy ﬁeld, and the di#erences in fertilizer application practice in hilly farm,
were clearly demonstrated by the broadband EM sensor.
Key words : Electromagnetic wave sounding, nondestructive investigation, Electrical conductivity.

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a  b  c  d  !  e 

Fig. .

Horizontal EC map obtained by multi-frequency EM survey.
(a) Forest West, (b) Forest South, (c) Tea farm, (d) orchard (plain), (e) orchard (hilly), (f)Paddy ﬁeld! " f #$-.8'()9: ; <=0 c d =>?)*'# @A*BC)DE

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10

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Vertical EC map obtained by multi-frequency EM survey.
(a) Forest West, (b) Forest South, (c) Tea farm, (d) orchard (plain), (e) orchard (hilly), (f) Paddy
ﬁeld (Before Inundation), (g) Paddy ﬁeld (After Inundation)

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11

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Vertical EC map of before and after rain in the forest obtained by multi-frequency EM survey.
(a) Forest West (Before rain), (b) Forest West (After rain), (c) Forest South (Before rain), (d)Forest South (After rain)

῍ῌTable -&'()*+,-

Volumetric water content changes before and after rainfall4
GEM-,.EC data at.131* Hz [mS m+]Site

Rainfall

Sampling
Depth (cm)West

before
after

+*
+*

*4+20
*4,,3

*4+10!
*4+-*!

*4,*1
*4.1*

*4,2-!
*4/23!

South

before
after

+*
+*

*4,*1
*4,/-

*4*/+!
*4*03!

,4-0,
,40,0

,4*0.!
,4*-+!

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a$ bQcd5efg

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u&vw

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12

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Table .



Ion chromatography of + : / soil extracted water4

Sampling Depth (cm)Forest West+*

Forest South+*PO. -
F
Cl
NO, Unit : mg L+
Br
NO-
SO.,

+243,
N4D4
04.,
+41*
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/410
+*421

+343+
N4D4
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N4D4
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*4.,
,*4/-

Paddy ﬁeld Tea farm Orchard (hilly) Orchard (plain)
+*
+*
+*
+*
,-4*/
N4D4
+4.
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N4D4
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,.4,

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N4D4
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N4D4
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ῌ

Corwin, D.L., Ka#ka, S.R., Hopmans, J.W., Mori, Y,
van Groenigen, J.W., van Kessel, C., Lesch, S.M.

0"12&345

and Oster, J.D. (,**-) : Assessment and ﬁeld-scale 6-78"9:"57&  ( Wenner

mapping of soil quality properties of a saline-array;<=*>" !"#"$%&

sodic soil, Geoderma, ++. (-) : ,-+ῑ,/3.

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Huang, H. (,**/) : Depth of investigation for small

7C"D+#E,&;C-F-G  

broadband electromagnetic sensors, Geophysics,

1* (0) : G+-/-G+.,.

0H"I./J?K*

"

)0

Huang, H. and Won, I. J. (,***) : Conductivity and῍ LM1N"234"O"PQ* 5susceptivility mapping using broadband electro-?K*)8 67"238R5J?K*)0

magnetic sensors, Journal of Environmental andU993"O;C:?

 ST*T*"
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Engineering Geophysics, / (.) : -+ῑ.+.
Mitsuhata, Y., Uchida, T., Matsuo, K., Marui, A. and2;&<2 ῌ =<2"OJ?K*)0

Kusunose, K. (,**0) : Various-scale electromag-

 S >V"WT2;"$234)

netic investigations of high-salinity zones in a%&

coastal plain, Geophysics, 1+ (0) : +01ῑ+1-.

῎

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5C7)?@

Rhoades, J.D., P.A.C. Raats and R. J. Prather. (+310) :?*$O)(Y ZDE2"[\FK*"

E#ects of liquid-phase electrical conductivity,00"GHJ?K*)0

water content, and surface conductivity on bulk

῏G "O "O* 5?K*)8 I]JK LM"^N#$%=O

soil electrical conductivity. Soil Sci. Soc. Am. J.
.* : 0/+ῑ0//.

P_(K*J?K*)0 K.-"[\&Wenner, F. (+3+0) : A Method of Measuring Earth*&= !F-. G `P!aQbc

Resistivity, Bulletin of the US Bureau of Stand-*ERde<]T fS?K*)I.(ards Science Paper +, (-).
Won, I. J., Keiswetter, D.A., Fields, G.R.A. and Sutton,῏῎

L.C. (+330) : GEM-, : A new multifrequency electromagnetic sensor, Journal of Environmental

T g h " 9 i " 5 7 & j U V k l m j g h W

and Engineering Geophysics, + (,) : +,3ῑ+-2.

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14

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