the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 08 Feb 2021
Impact of typhoons on particulate and dissolved 137Cs activities in seawater off the Fukushima Prefecture: results from the SOSO 5 Rivers cruise (October 2014)
Abstract. Cruise SoSo 5 Rivers took place during October 2014 off the coast of Fukushima Prefecture shortly after the passage of two typhoons. Detection of dissolved 134Cs and 137Cs in all samples reflected contamination caused by accidental releases of radiocaesium from the Fukushima Dai-ichi Nuclear power plant (FNPP1) accident. The dissolved activities were generally higher at coastal sites and decreased with distance from shore, and they were higher in the surface than in the bottom water. The tendency of 137Cs activities to decrease with distance from the coast reflected mixing of coastal water and open-ocean water of which 137Cs activity concentration was ~1.5 Bq m−3. At stations very close to the coast, we observed high particulate 137Cs activity concentration that exceeded dissolved 137Cs activity concentration. 137Cs activities were generally 1–2 orders of magnitudes lower in organic particles than in dissolved form, and the ratios of 137Cs activity concentration in organic particles to 137Cs activity concentration in dissolved form ranged from 0.01 ± 0.00 to 0.12 ± 0.01. The ratio of 137Cs to 134Cs activity concentrations in organic particles did not change with distance from shore or with 137Cs activity concentration and generally remained around 1, even in samples collected far from the coast. This pattern indicated that the organic particles had come from rivers or a source very close to the coast. The 137Cs / 134Cs activity ratio in dissolved form north of FNPP1 region was estimated to be 1.074 ± 0.015, a ratio that is in good agreement with the 137Cs / 134Cs activity ratio in the core of Unit 1 of the FNPP1 while the 137Cs / 134Cs activity ratio at Tomioka port which located south of FNPP1 was 0.998 ± 0.017. Therefore we can conclude the source of radiocaesium in seawater in the coastal region north of FNPP1 was deposited radiocaesium released from the core of Unit 1 of FNPP1, while the source of radiocaesium observed in the coastal region south of FNPP1 was a mixture of deposited radiocaesium released from the core of Unit 2 and the core of Unit 1 of FNPP1. During September–October of each year, the typhoon season in Japan, the 137Cs activity concentration generally increased at Ukedo port, Tomioka port, FNPP1, and Iwasawa beach, and showed a good relationship with the 7-day modified antecedent precipitation index (API) while there is less correlation between the modified API and 137Cs activity concentration near the outlet of canal from unit 5 and 6 of FNPP1 to the sea.
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RC1: 'Comment on bg-2020-491', Anonymous Referee #1, 08 Mar 2021
This work presents radiocesium in water and particles collected from the areas off the mouths of five rivers north of Fukushima Dai-ichi Nuclear Power Plant (FDNPP1) shortly after the passage of two typhoons. As the decrease of local atmospheric deposition and the direct discharge of radiocesium from the reactor, rive runoff input of radiocesium into the Pacific Ocean might become an important contribution. However, data presented in work did not give a clear picture about the impact of typhoon on particulate and dissolved 137Cs activities in seawater off the Fukushima Prefecture. The quality of writing, data presentation and results discussion do not meet the criteria to be accepted as a research article on Biogeosciences.
General comments:
- The quality of figures in this work are very poor. Some of the figure are hardly to see the values, and the trends as the authors described in the context, especially on paper print. Some of the figures can be plotted in a different way to make them more illustrative.
- Novelty and Objective. It is not very clear in the introduction what is the scientific question in this work? The novelty is not highlighted either, what is new in this study? Why the authors carried out the investigation to exam the radiocesium in water and particles? The sentence in line 86-87 is very confusing. The authors mentioned ‘to understand riverine fluxes in the coastal region’ but in the discussion on the ‘river fluxes’ and its connection to precipitation is very weak. It is still not clear how significant these ‘river fluxes’ contribute the total inventory of radiocesium in the study area.
- The definition of organic particle. The authors used concentrated nitric acid and hydrogen peroxide to process the samples and claim the obtained radiocesium was associated to organic form. I disagree to term this fraction as ‘organic particle’, because 1) the experiment details were not clear. What was the ratio between sample and reagents, what temperature was applied? 2) There was no data/literature to support the obtained radiocesium was only associated to organic matter. As concentrated nitric acid is a strong acid, it can easily dissolve inorganic radiocesium absorbed on the particle surface and can also extract radiocesium incorporated to the mineral lattices. Even though the authors reported the results of radioacesium for this ‘organic particle’ fraction, the interpretation and discussion on the results is not in depth. Why the authors analyzed radiocesium in ‘organic particles’? Why 137Cs activities concentration in ‘organic particles’ were one or two order lower than dissolved 137Cs (line 173), while 137Cs in all particles were higher than dissolved 137Cs (line 169)? How these results are connected to typhoon?
- 137Cs/34Cs ratio in particles. The authors in section 4.2 discuss the source term of 137Cs based on the 137Cs/134Cs in seawater, but why the authors did not discuss the obtained results for 137Cs/134Cs in particles? The authors claim the 137Cs/134Cs ratios in particle do not changes with distances but what are these values obtained in this work? Do they agree with the estimated ratios for FDNPP? Again, how typhoon impact the distribution of 137Cs/134Cs ratios?
- API calculation. I am not convinced by the API calculation approach. As the definition of K is not clear, what is the difference between K1, K2, …Kn, Why the authors set K to 1? Besides, from Fig. 17, the maximum value for R is about 0.5, meaning the R2=0.25. Therefore, none of these correlations is significant. I do not think it make much sense to perform such correlation analysis. Direct use of the metrological data (e.g., rainfall) would be sufficient to support the conclusion that high 137Cs activity concentrations in September-October were connected to the typhoon events.
- The language shall be improved thoroughly, as many descriptions are not concise. There are also repeated contexts.
Specific comments:
- Line 37: please give uncertainties for these 137Cs/134Cs ratios.
- Line 40: why the measurements were inaccurate? Please explain.
- Line 43-49: these are earlier findings about the different isotopic signatures on the particles affected by different units of FDNPP. The summary should be shortened to focus on the key point for this work.
- Line 62-74. These are also very tedious literature review. It is better to extract the most important findings which are relevant to this work.
- Line 157-159: these values are not reflected anywhere in the figures or table. These sentences should also be more concise.
- Line 162-165. These are somehow repeated sentences.
- Line 187-189: it is a very long sentence, please modify. Besides, it is not clear whether the findings about organic particles in this work agree with Naulier et al.
- The conclusion should be re-written. The conclusion shall not compile all the detailed results obtained from the work. It shall be more informative to let the reader understand the main points of the work and provides the reader with a sense of closure on the topic.
- 1. It is better to combine two figures, with one larger scale map indicating geographical positon and the current circulation pattern of the study area, and another details the sampling stations. It better to remove some of the annotations to the figure caption or use smaller fonts so it does not look so squeezed, and to use different symbols to mark different rivers so the reader can easily follow.6
- 2 and Fig. 9, they are very unclear. Why the authors do not use Ocean Data View to present the distribution of radio cesium on the surface water?
- Fig 3-7, the symbols are too small to be distinguished. The authors pull data for all stations in these figures, very hard to extract useful information. Why the authors do not use different symbols to present different rivers, so the reader can visualize the variations.
- 12-16 and Fig.19, I do not see the meaning for presenting these figures. All the figure do not show any statistical analysis data, based on the visual inspection, I do not see any of them have significant correlation. I would suggest remove them.
- 18. It is very hard to see the color change, especially after 2014. I suggest either delete the color bar data before 2013, or add another zoom-in figure for the data after 2014.
Technical corrections.
- Line 41: ‘small but significant’, this is a contradictory expression. Please modify.
- Lien 55: ‘primarily’ should be ‘primary’.
- Line 113: ‘disillusion’ should be ‘dissolution’.
- Line 127-138. There is an overlap with the description in ‘Data availability’.
- Line 150 and 155: please delete repeated data information ‘xxxdoi:xxxxx’, only keep the reference is sufficient.
Citation: https://doi.org/10.5194/bg-2020-491-RC1 - AC1: 'Reply on RC1', Michio Aoyama, 21 Apr 2021
-
RC2: 'Comment on bg-2020-491', Anonymous Referee #2, 09 Mar 2021
Comments on "Impact of typhoons on particulate and dissolved 137Cs activities in seawater off the Fukushima Prefecture: results from the SOSO 5 Rivers cruise (October 2014) (bg-2020-491)"
Recommendation: Accept, with major revisions noted.
General comments: I reviewed the manuscript " Impact of typhoons on particulate and dissolved 137Cs activities in seawater off the Fukushima Prefecture: results from the SOSO 5 Rivers cruise (October 2014) (bg-2020-491), submitted by Aoyama et al to Biogeosciences. The authors measured 134Cs and 137Cs in the dissolved and particulate samples contaminated by the Fukushima Dai-ichi Nuclear power plant (FDNPP1) accident, which presented some new data. Their spatial distribution reflected the mixing of coastal water and open-ocean water. The 137Cs/ 134Cs activity ratio derived from FDNPP accident is used to trace the source of riverine particle, which is very interesting. They also discussed the impact of typhoons on particulate and dissolved 137Cs activities in seawater off the Fukushima prefecture, but did not give a clear picture about the impact of typhoon on 137Cs activities in seawater. The novelty of this study needs to be improved. Additionally, decisions made with respect to data presentation combined with grammatical and other organizational errors result in a MS that lacks clarity and is difficult to follow. It is necessary to polish this manuscript by a native English speaker. Therefore, it is recommended to be published after major revisions.
Specific comments
-Line 14: What is indicated by the dissolved activities.......? 137Cs or 134Cs?-Line 18, “ranged from....to ......” means a range of variation, so the uncertainty in this sentence that “the ranged from 0.01±0.00 to 0.12±0.01” is redundant? Please note this in the MS.
-Material and methods: What are the detection limits of 134Cs and 137Cs?
-Lines 169-171, this sentence (the ratio of particulate 137Cs activity concentration......) is confusing, please rephase it.
- Lines 179-181. This sentence is too long and needs revise to improve clarity and the flow....
-Lines 206-211, what’s meaning that “data not shown or figure not shown”? Add in the Supporting information?
-Discussion section: The discussion was not enough and some conclusions are soft or from conjecturing, for example, “this pattern might reflect complex physical processes.....”(lines 210-211); “Possible explanation of this finding are that the radiocaesium in the coastal seawater........”(Lines 236-239). Additionally, API would be sufficient to support the conclusion that high 137Cs activity concentrations caused by the typhoon events, what about is the particle flux?
-Conclusions section: The conclusion section seems long with too much information on some discussion that appears unnecessary. The conclusion should be rephase.
-Data availability: it should be moved in the Material and methods?
-References: please unify the format of periodicals. For example, Scientific Reports (Line 349); J. Radioanal. Nucl. Chem. (Line 356).......
-Figures: these figures are not clear, please redraw.... For example, fig.2 and fig.9.
Technical corrections
-Line 36: ‘Nishihara et al. (Nishihara et al., 2012)’ should be ‘Nishihara et al. (2012)’.
-Line 43: ‘Miura et al. (Miura et al., 2020)’ should be ‘Miura et al. (2020)’.
-Line 57: ‘(Nagao et al., 2014)’ should be ‘Nagao et al. (2014)’.
-Line 115: ‘...the Low Level Radioactivity Laboratory At some stations, ....’ should be ‘...the Low Level Radioactivity Laboratory. At some stations, .....’.
-Lines 128, 320, 324: ‘Dataset of 134Cs and 137Cs activity...’ should be ‘Dataset of 134Cs and 137Cs activity...’.
-Line 188: ‘.....in the rivers, indeed Naulier et al. (Naulier et al., 2017)’ should be ‘......in the rivers. Indeed, Naulier et al. (2017)’.
-Line 224: ‘Tsurutal et al., (Tsuruta et al., 2014)’ should be ‘Tsurutal et al. (2014)’.
-Line 227: ‘1.06 (+-10%)’ should be ‘1.06 (±10%)’.
-Lines 235, 310: ‘0.92 (+-10%)’ should be ‘0.92 (±10%)’.
-Lines 314-316: ‘7-day, 5-7day’ should be ‘7-days, 5-7days’.
-Line 409, delete the Japanese language
-Lines 358-359, 410, 416, 420, 423, Superscript: 137Cs
-Table1, “+-“ changes “±”
Citation: https://doi.org/10.5194/bg-2020-491-RC2 - AC2: 'Reply on RC2', Michio Aoyama, 21 Apr 2021
Status: closed
-
RC1: 'Comment on bg-2020-491', Anonymous Referee #1, 08 Mar 2021
This work presents radiocesium in water and particles collected from the areas off the mouths of five rivers north of Fukushima Dai-ichi Nuclear Power Plant (FDNPP1) shortly after the passage of two typhoons. As the decrease of local atmospheric deposition and the direct discharge of radiocesium from the reactor, rive runoff input of radiocesium into the Pacific Ocean might become an important contribution. However, data presented in work did not give a clear picture about the impact of typhoon on particulate and dissolved 137Cs activities in seawater off the Fukushima Prefecture. The quality of writing, data presentation and results discussion do not meet the criteria to be accepted as a research article on Biogeosciences.
General comments:
- The quality of figures in this work are very poor. Some of the figure are hardly to see the values, and the trends as the authors described in the context, especially on paper print. Some of the figures can be plotted in a different way to make them more illustrative.
- Novelty and Objective. It is not very clear in the introduction what is the scientific question in this work? The novelty is not highlighted either, what is new in this study? Why the authors carried out the investigation to exam the radiocesium in water and particles? The sentence in line 86-87 is very confusing. The authors mentioned ‘to understand riverine fluxes in the coastal region’ but in the discussion on the ‘river fluxes’ and its connection to precipitation is very weak. It is still not clear how significant these ‘river fluxes’ contribute the total inventory of radiocesium in the study area.
- The definition of organic particle. The authors used concentrated nitric acid and hydrogen peroxide to process the samples and claim the obtained radiocesium was associated to organic form. I disagree to term this fraction as ‘organic particle’, because 1) the experiment details were not clear. What was the ratio between sample and reagents, what temperature was applied? 2) There was no data/literature to support the obtained radiocesium was only associated to organic matter. As concentrated nitric acid is a strong acid, it can easily dissolve inorganic radiocesium absorbed on the particle surface and can also extract radiocesium incorporated to the mineral lattices. Even though the authors reported the results of radioacesium for this ‘organic particle’ fraction, the interpretation and discussion on the results is not in depth. Why the authors analyzed radiocesium in ‘organic particles’? Why 137Cs activities concentration in ‘organic particles’ were one or two order lower than dissolved 137Cs (line 173), while 137Cs in all particles were higher than dissolved 137Cs (line 169)? How these results are connected to typhoon?
- 137Cs/34Cs ratio in particles. The authors in section 4.2 discuss the source term of 137Cs based on the 137Cs/134Cs in seawater, but why the authors did not discuss the obtained results for 137Cs/134Cs in particles? The authors claim the 137Cs/134Cs ratios in particle do not changes with distances but what are these values obtained in this work? Do they agree with the estimated ratios for FDNPP? Again, how typhoon impact the distribution of 137Cs/134Cs ratios?
- API calculation. I am not convinced by the API calculation approach. As the definition of K is not clear, what is the difference between K1, K2, …Kn, Why the authors set K to 1? Besides, from Fig. 17, the maximum value for R is about 0.5, meaning the R2=0.25. Therefore, none of these correlations is significant. I do not think it make much sense to perform such correlation analysis. Direct use of the metrological data (e.g., rainfall) would be sufficient to support the conclusion that high 137Cs activity concentrations in September-October were connected to the typhoon events.
- The language shall be improved thoroughly, as many descriptions are not concise. There are also repeated contexts.
Specific comments:
- Line 37: please give uncertainties for these 137Cs/134Cs ratios.
- Line 40: why the measurements were inaccurate? Please explain.
- Line 43-49: these are earlier findings about the different isotopic signatures on the particles affected by different units of FDNPP. The summary should be shortened to focus on the key point for this work.
- Line 62-74. These are also very tedious literature review. It is better to extract the most important findings which are relevant to this work.
- Line 157-159: these values are not reflected anywhere in the figures or table. These sentences should also be more concise.
- Line 162-165. These are somehow repeated sentences.
- Line 187-189: it is a very long sentence, please modify. Besides, it is not clear whether the findings about organic particles in this work agree with Naulier et al.
- The conclusion should be re-written. The conclusion shall not compile all the detailed results obtained from the work. It shall be more informative to let the reader understand the main points of the work and provides the reader with a sense of closure on the topic.
- 1. It is better to combine two figures, with one larger scale map indicating geographical positon and the current circulation pattern of the study area, and another details the sampling stations. It better to remove some of the annotations to the figure caption or use smaller fonts so it does not look so squeezed, and to use different symbols to mark different rivers so the reader can easily follow.6
- 2 and Fig. 9, they are very unclear. Why the authors do not use Ocean Data View to present the distribution of radio cesium on the surface water?
- Fig 3-7, the symbols are too small to be distinguished. The authors pull data for all stations in these figures, very hard to extract useful information. Why the authors do not use different symbols to present different rivers, so the reader can visualize the variations.
- 12-16 and Fig.19, I do not see the meaning for presenting these figures. All the figure do not show any statistical analysis data, based on the visual inspection, I do not see any of them have significant correlation. I would suggest remove them.
- 18. It is very hard to see the color change, especially after 2014. I suggest either delete the color bar data before 2013, or add another zoom-in figure for the data after 2014.
Technical corrections.
- Line 41: ‘small but significant’, this is a contradictory expression. Please modify.
- Lien 55: ‘primarily’ should be ‘primary’.
- Line 113: ‘disillusion’ should be ‘dissolution’.
- Line 127-138. There is an overlap with the description in ‘Data availability’.
- Line 150 and 155: please delete repeated data information ‘xxxdoi:xxxxx’, only keep the reference is sufficient.
Citation: https://doi.org/10.5194/bg-2020-491-RC1 - AC1: 'Reply on RC1', Michio Aoyama, 21 Apr 2021
-
RC2: 'Comment on bg-2020-491', Anonymous Referee #2, 09 Mar 2021
Comments on "Impact of typhoons on particulate and dissolved 137Cs activities in seawater off the Fukushima Prefecture: results from the SOSO 5 Rivers cruise (October 2014) (bg-2020-491)"
Recommendation: Accept, with major revisions noted.
General comments: I reviewed the manuscript " Impact of typhoons on particulate and dissolved 137Cs activities in seawater off the Fukushima Prefecture: results from the SOSO 5 Rivers cruise (October 2014) (bg-2020-491), submitted by Aoyama et al to Biogeosciences. The authors measured 134Cs and 137Cs in the dissolved and particulate samples contaminated by the Fukushima Dai-ichi Nuclear power plant (FDNPP1) accident, which presented some new data. Their spatial distribution reflected the mixing of coastal water and open-ocean water. The 137Cs/ 134Cs activity ratio derived from FDNPP accident is used to trace the source of riverine particle, which is very interesting. They also discussed the impact of typhoons on particulate and dissolved 137Cs activities in seawater off the Fukushima prefecture, but did not give a clear picture about the impact of typhoon on 137Cs activities in seawater. The novelty of this study needs to be improved. Additionally, decisions made with respect to data presentation combined with grammatical and other organizational errors result in a MS that lacks clarity and is difficult to follow. It is necessary to polish this manuscript by a native English speaker. Therefore, it is recommended to be published after major revisions.
Specific comments
-Line 14: What is indicated by the dissolved activities.......? 137Cs or 134Cs?-Line 18, “ranged from....to ......” means a range of variation, so the uncertainty in this sentence that “the ranged from 0.01±0.00 to 0.12±0.01” is redundant? Please note this in the MS.
-Material and methods: What are the detection limits of 134Cs and 137Cs?
-Lines 169-171, this sentence (the ratio of particulate 137Cs activity concentration......) is confusing, please rephase it.
- Lines 179-181. This sentence is too long and needs revise to improve clarity and the flow....
-Lines 206-211, what’s meaning that “data not shown or figure not shown”? Add in the Supporting information?
-Discussion section: The discussion was not enough and some conclusions are soft or from conjecturing, for example, “this pattern might reflect complex physical processes.....”(lines 210-211); “Possible explanation of this finding are that the radiocaesium in the coastal seawater........”(Lines 236-239). Additionally, API would be sufficient to support the conclusion that high 137Cs activity concentrations caused by the typhoon events, what about is the particle flux?
-Conclusions section: The conclusion section seems long with too much information on some discussion that appears unnecessary. The conclusion should be rephase.
-Data availability: it should be moved in the Material and methods?
-References: please unify the format of periodicals. For example, Scientific Reports (Line 349); J. Radioanal. Nucl. Chem. (Line 356).......
-Figures: these figures are not clear, please redraw.... For example, fig.2 and fig.9.
Technical corrections
-Line 36: ‘Nishihara et al. (Nishihara et al., 2012)’ should be ‘Nishihara et al. (2012)’.
-Line 43: ‘Miura et al. (Miura et al., 2020)’ should be ‘Miura et al. (2020)’.
-Line 57: ‘(Nagao et al., 2014)’ should be ‘Nagao et al. (2014)’.
-Line 115: ‘...the Low Level Radioactivity Laboratory At some stations, ....’ should be ‘...the Low Level Radioactivity Laboratory. At some stations, .....’.
-Lines 128, 320, 324: ‘Dataset of 134Cs and 137Cs activity...’ should be ‘Dataset of 134Cs and 137Cs activity...’.
-Line 188: ‘.....in the rivers, indeed Naulier et al. (Naulier et al., 2017)’ should be ‘......in the rivers. Indeed, Naulier et al. (2017)’.
-Line 224: ‘Tsurutal et al., (Tsuruta et al., 2014)’ should be ‘Tsurutal et al. (2014)’.
-Line 227: ‘1.06 (+-10%)’ should be ‘1.06 (±10%)’.
-Lines 235, 310: ‘0.92 (+-10%)’ should be ‘0.92 (±10%)’.
-Lines 314-316: ‘7-day, 5-7day’ should be ‘7-days, 5-7days’.
-Line 409, delete the Japanese language
-Lines 358-359, 410, 416, 420, 423, Superscript: 137Cs
-Table1, “+-“ changes “±”
Citation: https://doi.org/10.5194/bg-2020-491-RC2 - AC2: 'Reply on RC2', Michio Aoyama, 21 Apr 2021
Data sets
Dataset of 134Cs and 137Cs activity concentration concentrations in dissolved for, all particles and organic form of particles obtained by SoSo 5 rivers cruise in 2014 M. Aoyama, S. Charmasson, Y. Hamajima, and C. Duffa https://doi.org/10.34355/CRiED.U.TSUKUBA.00030
Dataset of 134Cs and 137Cs activity concentrations in dissolved form and, all particles at Tomioka, Fukushima in August 2014 M. Aoyama, S. Charmasson, Y. Hamajima, and C. Duffa https://doi.org/10.34355/CRiED.U.TSUKUBA.00031
Dataset of time series of radiocaesium activity concentrations at Tomioka, Fukushima during the period from 10 June 2014 to 24 April 2019 M. Aoyama, S. Charmasson, Y. Hamajima, and C. Duffa https://doi.org/10.34355/CRiED.U.TSUKUBA.00032
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