Top ＞ 137Cs and 134Cs activities in the North Pacific Ocean after Fukushima Nuclear power plants accident


137Cs and 134Cs activities in the North Pacific Ocean after Fukushima Nuclear power plants accident
Some preliminary results provided by the Meteorological Research Institute, Japan.

Japanese


　MRI (Meteorological Research Institute) measured the concentration of radiocesium (134Cs、137Cs) in the seawater sampled in April - May 2011.
　The sampling positions are located widely in the North Pacific Ocean (Figure 1).

Distribution of 134Cs and 137Cs activities in the surface seawater
Figure 1　Distribution of 134Cs and 137Cs activities in the surface seawater
(brown:NYK ships, aqua blue:MR11-03(Honda et al.,2011), blue:KT11-06)


The follwing tables shows the properties of the samples;sample ID, location, date (yyyymmdd), concentration.


Table 1　Radiocaesium activity in the North Pacific Ocean in April/May 2011 (part1)
sample ID Depth [dbar] Latitude Longitude Date 134Cs　[Bq/m3] 137Cs　[Bq/m3]
NYK11-043 0 34.95ºN 143.86ºE 20110331 135±10 150±8
NYK11-001 0 35.68ºN 143.77ºE 20110401 507±33 546±28
NYK11-003 0 36.60ºN 147.60ºE 20110401 1000±71 1080±60
NYK11-044 0 35.07ºN 146.44ºE 20110401 34±2.6 36.8±2.1
NYK11-007 0 38.18ºN 154.97ºE 20110402 17.7±1.6 21.5±1.3
NYK11-009 0 38.08ºN 158.58ºE 20110402 1.9±0.5 3.6±0.4
NYK11-046 0 35.12ºN 154.14ºE 20110402 9.5±1.1 11.3±0.8
NYK11-047 0 34.89ºN 158.76ºE 20110402 6.6±0.8 6.7±0.6
NYK11-048 0 34.76ºN 161.27ºE 20110402 2.6±0.5 3.6±0.4
NYK11-085 0 33.85ºN 141.31ºE 20110402 ND (<0.4) 1.7±0.2
NYK11-049 0 34.09ºN 173.28ºE 20110403 3.4±0.6 6.1±0.5
NYK11-086 0 34.33ºN 144.68ºE 20110403 158±11 181±9
NYK11-087 0 34.51ºN 148.40ºE 20110403 98.4±6.6 118±6
NYK11-050 0 35.09ºN 173.38ºE 20110404 0.7±0.4 2.4±0.3
NYK11-089 0 34.81ºN 153.51ºE 20110404 10.2±1.1 12.5±0.8
NYK11-090 0 34.98ºN 156.16ºE 20110404 2.7±0.7 6.1±0.6
NYK11-091 0 35.15ºN 158.93ºE 20110405 3.4±0.7 7.5±0.6
NYK11-092 0 35.32ºN 161.70ºE 20110405 3.4±0.6 5.3±0.4
NYK11-095 0 36.35ºN 178.99ºE 20110406 1.1±0.6 2.4±0.4
NYK11-021 0 41.12ºN 167.75ºW 20110407 ND (<0.4) 1.8±0.2
NYK11-023 0 42.33ºN 159.88ºW 20110408 0.6±0.3 1.9±0.2
NYK11-025 0 43.00ºN 151.95ºW 20110409 ND (<0.4) 1.8±0.2
NYK11-055 0 33.46ºN 154.15ºW 20110409 ND (<0.4) 1.4±0.2
NYK11-098 0 36.84ºN 163.23ºW 20110409 ND (<0.4) 1.9±0.2
NYK11-027 0 43.62ºN 143.57ºW 20110410 0.7±0.3 2.3±0.2
NYK11-056 0 32.52ºN 146.59ºW 20110410 ND (<0.4) 1.8±0.2
NYK11-100 0 35.88ºN 151.92ºW 20110410 ND (<0.4) 1.8±0.2
NYK11-125 0 33.29ºN 142.20ºE 20110410 3.1±0.6 3.5±0.4
NYK11-029 0 38.18ºN 134.97ºW 20110411 ND (<0.4) 1.4±0.2
NYK11-057 0 31.32ºN 140.20ºW 20110411 ND (<0.4) 1.9±0.2
NYK11-101 0 34.97ºN 146.43ºW 20110411 ND (<0.4) 2.0±0.2
NYK11-127 0 35.36ºN 147.57ºE 20110411 2.2±0.5 3.3±0.4
NYK11-102 0 33.92ºN 141.12ºW 20110412 ND (<0.4) 2.0±0.2
NYK11-103 0 32.50ºN 135.86ºW 20110412 ND (<0.4) 1.8±0.2
NYK11-129 0 39.01ºN 152.70ºE 20110412 1.9±0.4 3.6±0.3
NYK11-058 0 28.94ºN 130.73ºW 20110413 ND (<0.4) 1.6±0.2
NYK11-059 0 27.66ºN 126.44ºW 20110413 0.6±0.3 1.9±0.2
NYK11-104 0 31.02ºN 130.83ºW 20110413 ND (<0.4) 2.2±0.2
NYK11-131 0 42.20ºN 157.80ºE 20110413 8.9±1.4 16.8±1.2
NYK11-060 0 25.42ºN 120.36ºW 20110414 ND (<0.4) 1.5±0.2
NYK11-105 0 29.24ºN 126.05ºW 20110414 ND (<0.4) 1.8±0.2
NYK11-133 0 44.80ºN 163.82ºE 20110414 2.9±0.7 3.1±0.4
NYK11-137 0 46.25ºN 177.01ºE 20110416 2.3±0.6 2.8±0.4
NYK11-141 0 46.23ºN 169.31ºW 20110416 2.4±0.5 3.5±0.3
NYK11-143 0 46.23ºN 162.05ºW 20110418 2.7±0.6 3.0±0.4
NYK11-165 0 30.07ºN 131.81ºE 20110421 ND (<0.4) 1.7±0.2
NYK11-166 0 27.16ºN 131.24ºE 20110422 ND (<0.4) 1.5±0.3
NYK11-167 0 24.23ºN 130.48ºE 20110422 ND (<0.4) 1.6±0.3
NYK11-147 0 53.81ºN 146.08ºW 20110508 0.7±0.3 1.8±0.2
NYK11-301 0 36.49ºN 147.73ºE 20110509 30.0±2.6 38.2±2.3
NYK11-310 0 38.31ºN 156.66ºE 20110510 12.7±1.5 14.6±1.1
NYK11-151 0 53.41ºN 178.21ºW 20110511 ND (<0.4) 1.3±0.2
NYK11-307 0 41.31ºN 170.45ºE 20110511 3.2±0.6 5.1±0.5
NYK11-313 0 43.66ºN 170.30ºW 20110511 3.3±0.6 6.5±0.5
NYK11-317 0 42.86ºN 179.62ºE 20110512 164±11 196±10
NYK11-314 0 43.61ºN 160.96ºW 20110512 3.8±0.7 6.8±0.5
NYK11-319 0 42.72ºN 151.12ºW 20110513 13.5±1.5 13.8±1.1
NYK11-321 0 40.97ºN 141.46ºW 20110514 8.1±0.9 11.2±0.8
NYK11-175 0 15.70ºN 130.45ºE 20110515 ND (<0.4) 1.3±0.2
NYK11-322 0 38.76ºN 133.33ºW 20110515 1.5±0.4 3.7±0.4
NYK11-176 0 21.02ºN 131.77ºE 20110516 ND (<0.4) 1.9±0.3
NYK11-177 0 25.50ºN 132.92ºE 20110517 0.7±0.4 1.2±0.2
（last updated: March 12, 2012）



Table 2　Radiocaesium activity in the North Pacific Ocean in April/May 2011 (part2)
sample ID Depth [dbar] Latitude Longitude Date 134Cs　[Bq/m3] 137Cs　[Bq/m3]
KT1106-1 0 35.25ºN 139.77ºE 20110426 <120 <120
KT1106-2 0 34.87ºN 139.90ºE 20110426 <120 <120
KT1106-3 0 34.93ºN 140.87ºE 20110426 310±80 <120
KT1106-4 0 35.02ºN 140.95ºE 20110426 <120 <120
KT1106-5 0 35.55ºN 141.80ºE 20110427 <120 <120
KT1106-6 0 36.00ºN 140.83ºE 20110427 170±80 <120
KT1106-7 0 36.03ºN 141.13ºE 20110428 210±80 200±90
KT1106-8 0 36.52ºN 141.87ºE 20110428 <120 <120
KT1106-9 0 37.18ºN 142.67ºE 20110429 210±80 280±90
KT1106-10 0 38.15ºN 143.03ºE 20110429 <120 <120
KT1106-11 0 38.40ºN 142.83ºE 20110429 320±80 290±90
KT1106-13 0 38.27ºN 143.48ºE 20110430 210±70 270±90
KT1106-14 0 38.22ºN 143.78ºE 20110430 310±60 <120
KT1106-15 0 38.95ºN 143.88ºE 20110501 <120 <120
KT1106-16 0 39.75ºN 143.98ºE 20110501 <120 <120
KT1106-17 0 40.02ºN 143.07ºE 20110501 <120 <120
KT1106-18 0 40.35ºN 141.97ºE 20110501 <120 <120
KT1106-19 0 39.75ºN 142.12ºE 20110502 190±70 200±90
KT1106-20 0 39.48ºN 142.50ºE 20110502 220±80 310±90
KT1106-21 0 39.42ºN 143.37ºE 20110503 <120 <120
KT1106-22 0 40.82ºN 142.53ºE 20110504 <120 <120
（last updated: March 12, 2012）



Table 3 shows the depth-dependent radioactive Cs activities at 40.032ºN, 165.010ºE. Seawater was sampled by Keifu-Maru KF11-09 cruise. Integrating these data, water column Cs activity (inventory) was estimated as follows.


Table 3 A profile of radiocaesium activity at in the North Pacific Ocean in October by Keifu-Maru vessel of JMA.
Cruise-No. Station-No. Depth [m] Latitude Longitude date Temperature [deg C] Salinity [g/kg] 134Cs [Bq/m3] 137Cs [Bq/m3]
KF11-09 KS-3101 0 40.032 165.010 20111013 20.93 34.32 23.3±1.6 30.2±1.6
KF11-09 KS-3101 26 40.032 165.010 20111013 20.94 34.32 24.4±1.7 30.5±1.6
KF11-09 KS-3101 51 40.032 165.010 20111013 20.18 34.37 21.0±1.4 28.2±1.5
KF11-09 KS-3101 76 40.032 165.010 20111013 15.17 34.51 12.1±0.9 16.9±0.9
KF11-09 KS-3101 100 40.032 165.010 20111013 13.92 34.43 5.1±0.4 8.0±0.4
KF11-09 KS-3101 150 40.032 165.010 20111013 12.43 34.35 3.2±0.3 5.9±0.3
KF11-09 KS-3101 201 40.032 165.010 20111013 11.65 34.30 2.3±0.2 4.5±0.3
KF11-09 KS-3101 301 40.032 165.010 20111013 9.98 34.16 3.6±0.3 6.1±0.3
KF11-09 KS-3101 402 40.032 165.010 20111013 7.84 34.01 1.0±0.1 2.6±0.2
KF11-09 KS-3101 502 40.032 165.010 20111013 5.92 33.97 in detail checking in detail checking
KF11-09 KS-3101 601 40.032 165.010 20111013 4.99 34.03 ND (<0.4) 0.96±0.07
KF11-09 KS-3101 802 40.032 165.010 20111013 4.07 34.18 ND (<0.4) 0.57±0.06
(Updated on 15 Mar. 2012)


Description

Water sampling
　

  • We use CTD/Rosette system to collect sample seawater to obtain vertical profiles when we use research vessels. Sample volume ranged from 10 to 20 liters.
    • 　
  • Voluntary Observing Ships of Nippon Yusen Kaisha, NYK collected surface seawater during the cruise from Japan to several destinations basically one sample per day. Sample volume is 2 -4 liters.

    • Analytical procedures
    We use an improved AMP procedure with the ground-level gamma-spectrometer by Aoyama and Hirose (2008) as follows:
    1. Measure the seawater volume (5-100 liters) and put into a tank with appropriate size.
    2. pH should be adjusted to be 1.6-2.0 by adding concentrated HNO3 (addition of 40 ml conc.HNO3 for 20 litre seawater sample makes pH of sample seawater about 1.6).
    3. Add CsCl of 0.26g to form an insoluble compound and stir at a rate of 25 litre air per minute for several minutes.
    4. Weigh AMP of 4g and pour it into a tank to disperse the AMP with seawater.
    5. 1 hour stirring at the rate of 25 litre air per minute.
    6. Settle until the supernate becomes clear. A settling time is usually 6 hours to overnight, but no longer than 24 hours.
    7. Take an aliquot of 50 ml supernate to calculate the amount of the residual caesium in the supernate.
    8. Loosen the AMP/Cs compound from the bottom of the tank and transfer into a 1-2 litre of beaker, if it is necessary do additional step of decantation.
    9. Collect the AMP/Cs compound onto 5B filter by filtration and wash the compound with 1M HNO3.
    10. Dry up the AMP/Cs compound for several days in room temperature.
    11. Weigh the AMP/Cs compound and determine weight yield.
    12. Transfer the AMP/Cs compound into a Teflon tube of 4ml volume and subject to gamma-ray spectrometry.

    Underground gamma-spectrometry
    1. the same procedure from step 1) to step 12)
    2. Dissolve AMP/Cs compound by adding alkali solution
    3. pH should be adjusted to be ca. 8.1 by adding 2M HCl and adjust the volume of solution ca. 70-100ml.
    4. Perform precipitation of Cs2Pt(Cl)4 to add chloroplatinic acid (1g/5ml D.W) at pH = 8.1 and keep in refrigerator during a half-day.
    5. Collect the Cs2Pt(Cl)4 precipitate onto filter by filtration and wash the compound with solution (pH = 8.1)
    6. Dry up the Cs2Pt(Cl)4 precipitate for several days in room temperature
    7. Weigh the Cs2Pt(Cl)4 precipitate and determine weight yield
    8. Transfer the Cs2Pt(Cl)4 precipitate into a Teflon tube of 4ml volume and subject to underground gamma-spectrometry
    Reference
    Aoyama M., K. Hirose, Radiometric determination of anthropogenic radionuclides in seawater samples,In: Analysis of Environmental Radionuclides, Radioactivity in the Environment, Vol. 2, (Ed) P. P. Povinec, pp137-162, Elsevier, Hungary, 2008.

    Last updated: March 15, 2012