Properties and Management of Soil Damaged by the 2011 Huge Tsunami in Eastern Japan

Transcription

1 MARCO Symposium _24-27 Tsukuba Properties and Management of Soil Damaged by the 2011 Huge Tsunami in Eastern Japan Masami Nanzyo (Graduate School of Agricultural Science, Tohoku University) 1. Introduction 2. Physical impacts 3. Chemical impacts 4. Management of damaged farmlands (CG:NHK)

2 1. Introduction 3.11 Earthquake and Tsumami Hypocentral region CG & photos from the NHK TV program

3 Prosptect on restoration of farmland damaged by tsunami in every fiscal year (MAFF, ) Prefecture Others Total Iwate Miyagi 1,220 5,450 4,120 3, ,340 Fukushima ,350 1,200 2,450 5,460 Aomori, Ibaraki, Chiba Total 8,310 5,610 4,990 2,570 21,480 Percentage 39% 26% 23% 12% 100%

4 Tsunami 5 Paddy fields 3 Ridge 4 Paddy fields 2 Sand 1 Mud Farmlands Nearshore zone : Erosion 4 5 : Ion exchange, precipitation and deposition Na Ca,Mg,K CaSO 4. 2H 2 O, NaCl Sand and mud (Sea water) (soil) Interactions between Tsunami and farmlands

5 2. Physical impacts Tsunami Tsunami Erosion Erosion and deposition (Mud > sand)

6 85B Tilled plow layer Plow sole An example without damage

7 1.23 ds m -1 Tsunami deposit 1.55 ds m -1 Plow layer Rice stubbles remained in the field before tilling (1A) ds m -1 Plow sole

8 Tsunami deposit Plow sole Plow layer soil was probably removed.

9 1.23 ds m ds m -1 Ex.Na 9.1% 85B surface 85A surface 1.23 ds m -1 85A profile Ex.Na 23% Ex.Na 1.8% Crust-like form was found on the surface of 85A with almost no tsunami deposit.

10 Soil sampling Tsunami deposit 10 cm 1st layer 10 cm 2nd layer

11 Tsunami deposits on farmlands (Miyagi Pref.-Sendai City-Tohoku Univ.) Mud Sand Thickness (mud+sand) 0cm 1-5cm 6-10cm 11-40cm Soil An example of the deposits

12 3. Chemical impacts Properties of Tsunami deposits on farmlands in Miyagi Prefecture Minamisanriku Higashimatsushima High values (Miyagi Pref.-Sendai City-Tohoku Univ.)

13 2 nd layer 1 st layer Tsunami deposit <0.3, , , , >10 ds m -1 Vertical and horizontal distribution of EC(1:5) values. Tsunami deposit, especially mud layers, showed high values. (Kanno,2011)

14 2 nd layer 1 st layer Tsunami deposit No tsunami deposit, <5%, 5 15%, 15-25%, >25% Vertical and horizontal distribution of Na/(Ca+Mg+K+Na) values. (Kanno,2011)

15 At least two kinds of crystals, cubic and prismatic, were found on the dry mud deposit using SEM.

16 Na Cl NaCl O S Ca CaSO 4. 2H 2 O A powder XRD pattern of the crystals formed on the dry mud. The crystals found on the dry mud were mainly gypsum and NaCl.

17 Electrolytes in water Very high concentration in seawater Average seawater Average river water mm Cl SO HCO Na K Ca Mg Stumm & Morgan 9 rivers in Japan (1996) (1989)

18 Mud layer 2 nd layer Total S, N [mol kg -1 ] Total N Total S 2 nd layer Total C [mol kg -1 ] Total C [mol kg -1 ] Relationship between C and S. The total S content was more in the mud layer than in the 2 nd layer. Total N is shown for reference.

19 S Fe Energy [kev] Pyrite 2Θ(Cu,Kα)

20 4. Management of damaged farmlands Barley appeared to be tolerant against salts.

21 June 14 th, 2011 Sep. 4th EC(1:5) [ds m -1 ] June 14 th, 2011 Clay loamy Sandy NaCl was removed from sandy soil by rain.

22 Jun. 14 th, 2011 Sep. 4 th, 2011 Jun. 24 th, 2012 Changes in vertical distribution of EC(1:5) values with time. The tsunami deposit was removed after Sep. 4 th, 2011.

23 Jun. 14 th, 2011 Sep. 4 th, 2011 Jun. 24 th, 2012 Changes in vertical distribution of exchangeable Na + with time. The tsunami deposit was removed after Sep. 4 th,

24 Brassica plants grew normally under EC(1:5) value of around 2 ds m -1. Other crops also show normal growth in sandy upland soil.

25 With underground drainage For well-drained soil Irrigation Drain ditch Salts For poorly-drained soil Salts For poorly-drained soil without drain ditch Salts Salts Procedures to remove NaCl using irrigation water (MAFF, 2011)

26 Salt removal using irrigation water in the paddy fields. 2012_1_19

27 8.31, 2012 Arai in Sendai

28 Tsunami-affected areas in Miyagi According to historical and geological researches, Sendai plain was repeatedly hit by huge Tsunamis Heisei 1611 Keichou 869 Jogan 4 5 km (Inundation distance) (The Ministry of Public Management) B.P Yayoi Minoura and Nakaya, 1990; Iinuma 1995; Matsumoto et al., 2011.

29 There was Tsunami deposit (2011) Ap Volcanic ash (915) Muck Tsunami deposit (869) Loamy sand

30 Summary 1. Farmland soil was dug along roads and ridges by tsunami. 2. Soil removal was weak in the paddy fields before tilling while the plow layer soil was removed partially or completely after tilling. 3. Free NaCl can be removed by water while a decrease in exchangeable Na is slow. 4. If Ca is deficient in crops or soil physical properties are deteriorated due to high ex. Na, Ca application is needed. 5. Inorganic S such as gypsum and sulfides increased in the tsunami deposit although those were mostly removed from farmlands. 6. Reinforcements of drainage and pumping system are needed in the coastal areas with a very low altitude due to land subsidence. Acknowledgement: This work was supported by the Implementation-Support Program of the Japan Science and Technology Agency, Asahi Industries Co., Ltd., and The Naito Foundation. The author thanks Sendai City, Miyagi Prefecture, Drs. T. Ito, T. Takahashi, and H. Kanno of Tohoku University for collaboration in the soil survey, sampling, analytical works and many other assistances.

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