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f «ffe#«i^p^fe«j:y f^± (top-soii) frbzarm (sub-son) '\ i37 ,37 ®mmm(nmij\c£^ffi'Pi-& cs(DfrMim%¥mmmm7^mT\ ££>c cs Residence half-time of 137Cs in the top-soils of Japanese paddy and upland fields Misako KOMAMURA, Akito TSUMURA*. Kiyoshi K0DA1RA** National Institute of Agro-Environmental Sciences, *ex-National Institute of Agro-Environmental Sciences, **Prof. Em. Ashikaga Institute of Technology A series of top-soil samples of 14 paddy fields and 10 upland fields in Japan, were annually collected during more than 30 years, to be examined in the contents of ,37Cs. The data, which were obtained by the use of a gamma spectrometric system, received some statistical treatments to distinguish the annual decline of 137Cs contents from deviations. Then the authors calculated "residence half-time of137Cs" within top-soil, and "eluviation rate of 137Cs" from top to the sub-layer of the soil. The following nationwide results were obtained irrespective of paddy or upland fields: (1) The "apparent residence half-time" was estimated as 16—-17 years. This one consists of both effects of eluviation and nuclear disintegration. (2) The "true residence half-time" was reported as 41~~42 years. This one depends on the eluviation speed of 137Cs exclusively, because the influence of nuclear disinte• gration has been compensated. (3) The eluviation rate of 137Cs from top-soil down to the sub-soil was 1.6—-1. 7% per year. (4) The ratio of distribution of 137Cs between top-soil and the sub-soil was estimated to be 6:4 as average at the date of 1996. Keyword: 137Cs, paddy soil, upland soil, residence half-time, eluviation rate -12- JAERI-Conf 99-001 1 . litau: 7Km^'\^^ l37cs^aosrK¥(Difrtt&mmzmmM^wi-zm£te±m(DMm^mjf$ «S&£K«fc»)JI&£26*\ ±kLX&mfre>%miilpn?lfo 20cm £X* 37 ao l) XtrnZtltz* - %ZM%\^ % *«£"CW\ ^n^(7)^iffi(7)^^7XE0ft±^=kC/'Jfflft±4'(7) 137Cs(7)^^^^aS^t$- 2 . W5S^;i 2. 1 ±SBsm £ Fig. lH^Lfco 7jcff8&=kW *0JR«&K$®;*ft;fc>!fcffl • *H ftlWlXm^mVdMtel?* 2mm<7) Aft&#Lfc0 JAPAN SEA 2. 2 fKfstt:S0)&S • ft^ Joetsu >'V)7 2kffl±«li Table 1 \Z m±m\t f l y KounosuftKumagaya,, ^WMit1 o , nFutaba-cho* '*t^LuMkaw a Table 2 KjSLfco p 2. 3 #^±ig+<7) 137Cs<7) PACIFIC OCEAN H«lS!Ge*a»ft«aiS (Canberra atS GR1820, ffltt&$l. 8%, X* ;i/^-^D¥li2.0keV) Zffix.tzr Fig.1 Sampling sites in Japan 13- JAERI-Conf 99-001 Table 1 Soil properties of top-soils in paddy fields Sampling sites Soi 1 group Soil Depth pH Sand(2-0.02mm) Clay(<2tfm) Humus CEC** texture' (cm) (HJO) contents(X) contents(X) contents(X) (meq/IOOg) Japan Sea side Sapporo. HOKKAIDO Wet Andosols LiC 0-10 6.22 41.3 26.7 3.89 28.9 Akita. AK1TA Gley soiIs LiC 0-12 5.03 30.5 30.7 2.35 25.7 Joetsu. NIIGATA Gley soiIs LiC 0 12 5.59 26.0 39.5 4.13 30.8 Nonoichi, ISHIKAWA Gley Lowland soiIs CL 0-14 5.80 39.6 23.3 1.79 16.4 Totton, TOTTORI Gley Lowland soiIs LiC 0 14 5.57 35.4 29.1 2.88 19.2 Tsukushmo, FUKUOKA Gley Lowland soiIs CL 0 10 S.56 61.9 17.0 2.18 16.4 Regional average 0 12 5.80 39.1 27.7 2.87 22.9 Pacific Ocean side Monoka, IWATE Net Andosols LiC 0 12 6.42 40.4 31.6 11.71 55.8 Naton, M1YAGI Gley Lowland soiIs HC 0 12 5.73 21.9 47.6 2.74 43.4 Mito, iBARAK 1 Andosols LiC 0 13 6.45 48.1 28.1 7.29 36.4 Kounosu, SAITAMA Gley Lowland soiIs LiC 0-12 5.70 39.4 27.1 0.82 17.3 Tachikawa. TOKYO Brown Lowland soiIs LiC 0 IS 5.46 35.5 31.9 4.61 33.2 Futaba-cho, YAMANASH Gley Lowland soiIs SCL 0-12 5.66 71.6 15.1 0.95 10.3 Habikino. OSAKA Gley Upland soiIs CL 0 10 6.40 55.0 21.5 2.93 17.9 Sanyo-cho. OKAYAMA Gley soiIs CL 0-15 5.75 53.1 23.4 1.61 13.8 Regional average 0 13 5.95 45.6 28.3 4.08 28.5 Nationwide average 0 12 5.88 42.4 28.0 3.5S 26.1 * LiC:hght clay CLtclay loam HC: heavy clay SCL'-sandy clay loam *» cation exchange capacity Table 2 Soil properties of top soils in upland fields Sampling sites Soi1 group Soil Depth pH Sand(2-0.02mm) Clay(<2tfm) Humus CEC** texture* (cm) (H*0) contents(X) contents(X) contents(X) (meq/IOOg) Japan Sea side Sapporo, HOKKAIDO Net Andosols LiC 0-15 5.52 36.1 32.8 8.53 48.0 Nagaoka, NIIGATA Gley soiIs HC 0 15 5.59 10.5 51.6 4.47 40.0 Anagi, FUKUOKA Gley Lowland soi Is LiC 0 15 6.56 42.9 26.2 6.53 34.9 Regional average 0-15 5.89 29 8 36.9 6.51 41.0 Pacific Ocean side Monoka, IRATE Net Andosols CL 0 15 6.02 47.1 20.2 10.71 45.0 Iwanuma, MIYAGI Gley Lowland soiIs HC 0 15 5.73 21.9 47.6 2.74 43.4 Mo, 1 BARAK I Andoso1s LiC 0 15 6.00 46.8 25.7 6.03 39.4 Kumagaya, SAITAMA Gley Lowland soiIs CL 0-15 5.00 48.4 20.6 0.99 16.3 Tachikawa, TOKYO Brown Lowland soiIs LiC 0 15 5.46 41.2 28.2 5.22 29.3 Futaba-cho. YAMANASH1 Gley Lowland soi Is SCL 0-15 5.66 63.4 18.8 1.11 14.6 Sanyo cho, OKAYAMA G1ey soi1s CL 0 15 7.05 53.0 22.6 1.80 13.2 Regional average 0-15 5.85 46.0 26.2 4.09 28.7 Nationwide average 0-15 5.86 41.3 29.4 4.81 32.4 * LiC:hght clay CL:day loam HC'.heavy clay SCL:sandy clay loam ** cation exchange capacity -14- JAERI-Conf 99-001 'csotkMmmfezn-itzo 3.n&&m±m& 3. 1 *ffl-jaBft±0,3TCs£M0fr£Jf# *W4^Bfl*&^nfcl958^^t>1993^*t?(D35^raK:*Jlt-57KBa • *B!f¥±<7)£ 137Cs£fi<7) l37 7m-Mi'¥±(D cs$m(D\s-2\mt&¥(Dm&xmttm£mm£fttz0 ztibam mt, i%4*-im*tm\*-\m*(Dmm£Mm\zftt>fttz±%mft±mm®%mm(Dm (Dmmmts frtfmtisttzyt-frTVh i37cs(Dm±^i:^m^mmm%4^xm^- >7\z]s.-3ux^z>t\<^%%.w3iTf\(Dm.^m3) i:(5(i-iLTi^„ \m&%-mzmwLLtzo &tz\m*\z*x.)\,j-?4 *)w^FM%mmz& 16 14 • Paddy fields ° Upland fields C 12 E cr CO ^5 10 o 8 *J 'E 8 o ID O ^ 6 8 ID CC ° * .s ...°s. • • • ■Ir -8°he§!BS88iBs8 =ieIeB!iSSSM 1960 1970 1980 1990 year Fig.2 '"Cs contents of top-soils collected from 14 paddy fields and 10 upland f ieIds in Japan 3. 2 *ffl'flHfr±(Dl3TCs£;t(D«'>| F\g.2(DmMz^LtzM'o, 7j 15 JAERI-Conf 99-001 D Paddy f ields s.□ □ Decline curve A Y=5.0e-OO4,t D r=-0.967*** D a.. ti/2=16.9y 3- Dr>-rD 2-\ —dB"-.jgD Base year n "'Oaj^j-] 1 i i i i i i i i i i i i i l I I I i i i i i i > i i i i i i i i ■ ■ i i i i I 1960 [1964] 1970 1980 1990 year 3 Decline curve A Comprehensive time course of the cumulative contents of ,37Cs in the top-soils of paddy fields Each mean value of 14 fields is plotted without revision ***:p<0.001 6- Paddy fields $ A Decline curve C 5- v„j><> Y=4.9e"0,7t V A X"'-A-A.„. A r=-0.853*** v^. /*'*—- ti/2=40.7y 4- ^t OA^'^V. A A v-^ a A" -A— -AAA A 3 O <►'$-.<> A A Decl ine curve B <> <*._ Y=4.9e-°-040t *'Z'*-S o 2 1 Base year r-0.968'" * *>-^fto I ti/2=17.3y 1 'll I lI lI I I I II I I I I I I I I I I I I I I I l I I I I I I I I l l I I l ll' 1960 [1964] 1970 1980 1990 year 4 Decl ine curve B Time course of the contents of ,37Cs which have been accumulated in the soils up to the base year 1964 Each of the amounts of 137Cs,newly-captured by soils after 1964,is subtracted from the corresponding point in the Curve A ***:p<0.001 Decline curve C Revised curve excluding radioactivity decay from the Curve B ***:p<0.001 16- JAERI-Conf 99-001 Upland fields C° A D - □ Decl ine curve A JX 4 04,t CO X n Y=4.5e"- r=-0.964*** CO °X t,/2=17.0y a ° 0 4-> C w 0- a-- Base year °D~"qJ3-ejp * I I I I I I * I I I I I I I I I rTTTTTTTTT'Pr III I I I I1 lOTO 100a I960 [1964] 1970 1980 1990 year Fig 5 Decline curve A Comprehensive time course of the cumulative contents of ,37Cs in the top-soils of upland fields Each mean value of 14 fields is plotted without revision ***:p<0.001 Upland fields Decline curve C $>, Decline curve B o ',<>-$. Y=4.4e"°-039t $'^--- ° Base year r=-0.956*** 00^ ti/z=17.6y 1 1 III 1 1I I 1 1 I I 1 1 I I I I I I I I I 1 I I I I I I I l 1 1 1 I 1 1 I 1960 [1964] 1970 1980 1990 year Fig.6 Decline curve B Time course of the contents of 137Cs which have been accumulated in the soils up to the base year 1964 Each of the amounts of 137Cs,newly-captured by soils after 1964,is subtracted from the corresponding point in the Curve A ***:p< 0.001 Decline curve C Revised curve excluding radioactivity decay from the Curve B ***:p<0.001 - 17 - JAERI-Conf 99-001 m*ztfytjin'pmm*nt2o ^(D-mtLx^m^^M^^m^±\t?\g.^^m^±\t?\g.^^^ Ltz: Y = Xe kl (»£ 1) tztzlYte 137Cs-^ft Xlig^UfcltS 137Cs-^M x&^r$\zM-fz>ffi>js&$i ^mmm\fmhLx\i.ntmmzx^x lnY = lnX-A t (ftj£2) (omtix, ^t(nmm£.**ihxx&&vx(nm*mtzo ■torn Y(D%mtixi37cs(ommzmfe}E(D£±nmz&^xm^z(Di)\ TKeaitiii Fig. 3, *Hft±liFig. 5 So r 3. 3 ffi%¥ffimmt%®im ±s5W«t-5 34^ffi-C*^Lfcfe**, 7Kfflft±fiTable 3(Cj[fflft±liTable 4fc^Lfc«, «'> M%Bfrt>WfeltzfrMi(Offi'g¥ffimr$ (RHT-B) Ji^S^^-CTKfflftili 17. 3^. *fflfF± Ji 17.6^fcftofc„ ;*££, «'>ffl«IC^f)*^Lfcll©«ff@^«I^P^ (RHT-C) (2£|!¥#J ■C7KBaflF±»i40. 7^-Cflllft±tt42. 4*£fc ft o fc„ ft±a*£*0)TB'\0)-5MSa^fc 0 <7)M* £*£Lfc*££, £gTOT*7Kfflf^±tel.7%WP±m.6%^frofco «?e^«l^rP^ (RHT-B) • (RHT-C) fcitf&Bmi* *AP^i£^§3tf) £>ft*:0 f©!*©- - 18 - Table 3 Residence half-tine in top-soil and eluviation rate froi top-soil to the subsoil of ,37Cs in the paddy field Residence half-tiae (B) Residence half-tiae (C) and eluviation rate (RHT-B) (RHT-C) (ER) Sasp1ing sites n Regression Correlation RHT-B Regression Correlation RHT-C ER equation coefficient(r) (year) equation coefficient (r) (year) (X/year) Japan Sea side Sapporo, HOKKAIDO 27 Y= 2.9e" oes' -0.879*** 10.6 Y= 2.9e ° 042t -0.767*** 16.3 4.24 Akita, AKITA 29 Y= 6.5e ° 0311 -0.958*** 22.2 Y= 6.5e "■ 008t -0.659*** 85.0 0.82 Joetsu, NIIGATA 26 Y=14.2e" 059t -0.936*** 11.8 Y=14.2e"° 036t -0.849*** 19.4 3.57 Nonoichi, ISHIKAWA 21 Y=10.2e~° 02S' 0.853*** 26.6 Y=10.2e °- 003t -0.182 Tottori, TOTTORI 20 Y= 6.6e" 0311 0.952*** 22.4 Y= 6.6e ° 0081 -0.618** 88.9 0.78 Tsukushino, FUKUOKA 15 Y= 4.2e ° 050t -0.859*** 13.7 Y= 4.2e° 027t -0.673" 25.3 2.73 Averages of Individual data 138 Y= 6.9e° °48' -0.496*** 14.6 Y= 6.9e ° °25' -0.283** 28.3 2.45 Year 1 y data 29 Y= 7.0e ° °43' -0.972*** 16.0 Y= 7.0e° 02°' -0.889*** 34.3 2.02 Pacific Ocean side Morioka. IWATE 28 Y= 4.0e" 03" -0.865*** 22.1 Y= 4.0e ° 008t -0.415* 83.4 0.83 Natori, NIYAGI 20 Y= 4.8e-°' °32' -0.917*** 21.8 Y= 4.8e"° 009< -0.533* 79.6 0.87 Mito, IBARAKI 22 Y= 3.0e° 053t -0.837*** 13.1 Y= 3.0e ° 030< -0.648** 23.2 2.99 Kounosu, SAITAMA 17 Y= 3.7e" °40' -0.791*** 17.3 Y= 3.7e" 0,7t -0.480* 40.8 1.70 Tachikawa, TOKYO 19 Y= 4.2e °- 027t -0.875*** 25.3 Y= 4.2e"° 004t -0.275 67 Futaba-cho.YAMANASHI 22 Y= 3.3e ° ° ' -0.945*** 10.3 Y= 3.3e"° 044t -0.885*** 15.6 4.44 3 Habikino, OSAKA 28 Y= 1.5e" ° *' -0.825*** 20.2 Y= 1.5e ° 0,,t -0.431* 61.7 1.12 25 Sanyo-cho, OKAYAMA 18 Y= 2.9e ° ° ' -0.737*** 27.4 Y= 2.9e° °02' -0.094 Averages of Individual data 174 Y= 2.9e° 033t -0.498*** 21.3 Y= 2.9e ° 009t -0.165* 73.2 0.95 Yearly data 29 Y= 3.1e"' °34' -0.937*** 20.3 Y= 3.1e" °'1' -0.658*** 62.4 1.11 Nation wide averages of Al 1 of the data 312 Y= 4.4e-°' °42' -0.466*** 16.5 Y= 4.4e"° 0,,t -0.231*** 36.7 1.89 Yearly data 29 Y= 4.9e"°- °40' -0.968*** 17.3 Y= 4.9e"0' 0,7t -0.853*** 40.7 1.70 ***: p< 0.001 **: p< 0.01 *: p<0.05 n: Nuaber of saaples analyzed Y: 137Cs contents in paddy top-soil at the t year after 1964(kBq/i2) Table 4 Residence half-time in top-soil and eluviation rate froa top-soil to the sub-soil of 137Cs in the upland field Residence half-time (B) Residence half-time (C) and eluviation rate (RHT-B) (RHT-C) (ER) Sampling si tes n Regression Correlation RHT-B Regression Correlation RHT-C ER equation coeff icient (r) (year) equation coefficient (r) (year) (X/year) Japan Sea side Sapporo, HOKKAIDO 27 Y= 3.7e ° 042t -0.924*** 16.5 Y= 3.7e ° °"" 0.736'** 3B.B 1.89 Nagaoka, NIIGATA 28 Y= 8.9e ° 037t -0.956*** 18.6 Y= 8.9e" 0,4t -0.780*** 48.7 1.42 Amagi, FUKUOKA 15 Y= 3.1e ° 029t -0.886** 24.0 Y= 3.1e" ooet -0.363 Averages of Individual data 70 Y= 4.Be" 032t -0.475*** 22.0 Y= 4.6e" 009t 0.145 80.9 0.86 Yearly data 29 Y= 5.1e ° 031t -0.831*** 22.7 Y= 5.1e" 008t -0.347 91.9 0.75 Pacific Ocean side Morioka. IWATE 27 Y= 3.8e ° 0304 -0.887*** 23.1 Y= 3.8e ° 007t -0.411* 98.4 0.70 Iwanuma, MIYAGI 11 Y= 5.2e ° 063t -0.878*** 11.1 Y= 5.2e" 040t 0.758** 17.5 3.95 Mito. IBARAKI 21 Y= 3.4e ° 066t -0.887*** 10.5 Y= 3.4e" 043t -0.782*** 1B.1 4.32 Kumagaya, SAITAMA 27 Y= 5.7e" 075t -0.953*** 9.2 Y= 5.7e" 054' -0.914*** 12.9 5.37 Tachikawa. TOKYO 21 Y= 4.1e" °351 -0.801*'* 19.9 Y= 4.1e" °12' -0.41B 58.2 1.19 Futaba-cho.YAMANASHI 15 Y= 3.0e" 037t -0.908*** 18.9 Y= 3.0e" 014t -0.628* 50.8 1.37 Sanyo-cho. OKAYAMA 24 Y= 2.8e ° 024t -0.821*** 28.5 Y= 2.8e ° 00" -0.074 Averages of Individual data 146 Y= 3.7e" 043t -0.741*** 1B.3 Y= 3.7e ° 0204 -0.454*** 35.3 1.96 Yearly data 29 Y= 3.8e ° 041t -0.952*** 16.9 Y= 3.8e" 018t -0.808*** 38.5 1.86 Nation wide averages of Al1 of the data 216 Y= 4.1e ° 04M -0.631*** 1B.8 Y= 4.1e ° 018t 0.340*** 37.7 1.84 Yearly data 29 Y= 4.4e" 039t -0.956*** 17.6 Y= 4.4e" oiet -0.805*** 42.4 1.63 ***: p< 0.001 **: p< 0.01 *: p<0.05 n: Number of samples analyzed Y: 137Cs contents in uplund top-soil at the t year after 1964(kBq/m2) JAERI-Conf 99-001 o£±»<0l4K0)iiv^#£f,ft6j&*, *W&xm^tz±m 137cs©»@*«i^p^fc^»i^fc©B8^{i^^©«wgiija-c«t)So ttz. mmm\zB^mmt *¥#ffil"CJtl8 (Table 3, 4) Lfcch-5, 7kBaft±"CJiir*©^^*«J: 0 kJs^flfft^fS ^xb<*t>\zmi*maiZ><&mtf$>Zo *w%.xnhtitiffi®¥Wiiiffi (RHT-B) ttonz\h™tf&wxmmfcix&tem8¥im P*l (Jgffi5-10cmT*#jl5^) fcttR-tfttf, lu^(D^^^^=t 0 ^b^ ^ ^^ffi|6]^'^^n^o & e) tz, ffi^mmffl (RHT-B) ICO^T, *wfttm£7mft± (tkm) *m^tnh*t> n? yA- y*yy^T')\/frhnhfttz 137cs<7)fii {&Mi(n%iWftm*t>m%) fctt«Lfci:- 5*^©^^^^^^^?^, ~ft^(DMmvfftk^n-^;i/7*-;i/77 hx l37 Fig.4,6©«'>ffl«lCK:fe^T, 137Cs(7)$'>i!)-a-£, 1964^t>1979^£Tfc 1980^£ im*?txt*im'tti\*, w% - 21 - JAERI-Conf 99-001 3. 4 i37cs<7)7jcffl -mft±k* l3r / LXt$ mtttmbmpwm (5%*) £Fig.7 \z^Lti0 M#©#*«fl£{i±*K«fc9*,*fc£^j&* sft?>*ifc. &tz, fcrnhmtZtiM-tzk, \k^(D^t^^^±\z^ 100 r top-soil sub-soil 100 - Fig.7 Estimated distrbution rate of 137Cs in top-soil and the sub-soil of 10 fields at 1996 +: Paddy field *: Upland field 4. £ 7kM'>\^mkixit± (top-soii) *(Dl37cs*mi-tz>o 7km -mft±* (D®Mm*#tbtza wm(D7km • mft±* ia7cs %±(D®$kBZ^tztz^tzo z.^izmnzmit'to <**>£, MM^^i^w^-r - 22- JAERl-Conf 99-001 (i) mmm&wftm^m&mwmm, mim-mzm (1959-1995), n^&mjr (2) Y)i^~yA¥mfc&n!,miz£z)tfy-?i&^>7huj MJ-, nMmmyZisv-z. n ¥&ffifr (1990) (3) WtiJit*, JE»»E, S+JgaJtA, £H # : ^*W3E0f8M^ &36-f\ ^#!ffi3E0f (1996) (4) #ttHSA, ISJ+t^feT-. ^#%m : ±m&&V±m-mtio%fc#tfZ>fttt&Zhuy*t; Mst-ki/yMsOmmz.M'tZWfa IifiW5£0liS, B36.57-113 (1984) (5) Bunzel.K., Kofuji,H., Schimmack, M. : Residence time of global weapons testing fallout 237Np in a grassland soil compared to 239,240Pu, Z41Am and 137Cs, Health physics, 68,89-93 (6) Yamamoto, M. ,Sha, L., Kofuji, H., Tsumura, A., Komamura, M., Yuita, K. and Yamasaki, S. : Distribution and behavior of transuranium elements in paddy surface soil, Improvement of Environmental Transfer Models and Parameters, Proceedings of Nuclear Cross-Over Research, 198-206, Promotion Committee on Nuclear Cross-Over Reseach, Japan (1996) (7) Schimmack, W., Bunzl.K. and Zelles, L. :Initial rates of migration of radionuclides from the Chernobyl fallout in undisturbed soils, Geoderma, 44, 211-218 (1989) -23-