the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 15 Jan 2024
Variation of atmospheric 137Cs and possible carriers in aerosol samples obtained in Namie in a heavily contaminated area of Fukushima prefecture in 2019
Abstract. A lot of radionuclides were released into the environment from Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on March 11, 2011. Because of the long half-life (30.12 years) and high-concentration deposition about 137Cs, the study regarding on the distribution of 137Cs in aerosol samples and the understanding carriers of 137Cs became a hot topic in the recent decade. However, even nine years after FDNPP accident, the explanation for the fluctuations of 137Cs and their carriers in the atmosphere remains elusive. In this study, a small fluctuation within 0.0002 Bqm-3 from January to April and a slightly higher level of atmospheric 137Cs from May to September was still observed in the aerosol samples obtained in Namie in a heavily contaminated area of Fukushima prefecture in 2019. Therefore, new observations, obtaining by fluorescent upright microscope and scanning electron microscopes (SEM) equipped with an energy dispersive X-ray spectrometer (EDS), quantitatively demonstrated that the carriers of 137Cs were the combination of C-particles and Al-particles (Al-particles was dominated with the percentage of 68 %) in early May; meanwhile the predominate carriers of 137Cs were carbonaceous particles with the average percentage of 88 % in late May and September. Significantly, small particles (less than 2 μm) and medium particles (2–8 μm) of carbonaceous particles had a higher level in the aerosol samples of May and September. Specially, little particles (less than 1 μm), bacteria (1–1.8 μm), and spores (1.8–10 μm) had a linear relationship with the distribution of atmospheric 137Cs in the aerosol samples of September. In addition, the temperature and the precipitation were the main impact factors on the distribution of 137Cs and its carriers.
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Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-2999', Anonymous Referee #1, 06 Feb 2024
General comments
In this manuscript, there are three critical flaws, hindering publication.
Firstly, the authors did not directly measure 137Cs concentration of the aerosol samples, resulting in overinterpretation. Although they measured 137Cs concentration in the atmosphere during the observed period and compared it with the number and/or type of particles trapped in the filter, this evidence seems insufficient and indirect for identifying the source of the particles. Why not use imaging plates, as suggested by Tang et al. (2022) and Igarashi et al. (2019a), which were cited in the manuscript. Furthermore, I could not understand how the authors detected and counted each particle in a quantitative way. For example, how many particles were identified in the 12-mm diameter sections from the middle or edge area of the aerosol filter? How were areas for microscope images selected? More detailed raw data should be show, as demonstrated by Igarashi et al. (2019b) and their supplementary files.
The second flaw is the absence of basic scientific data. The abstract and conclusion stated that the authors continued monitoring from January to September and discussed seasonal variations in 137Cs-bearing aerosol samples. However, this study was actually a snapshot―they collected aerosol samples only in few days only in April, May and September, as shown in Table 2. I could not recognize the meaning of their excuse of “The absent samples in late May and early September 2019 were ascribed to the sampling plan and summer vacation.” (L. 115–116). Were data for monitoring periods not listed in this table taken from other references? In addition, in Figure 2 and 3, I found that horizontal axes of line graphs were not continuous and there are unexplained break axes. This is totally inaccurate in research.
The third flaw is that the objective of this manuscript was unclear. The introduction section was scattered in several directions. Its starts with general information on reactor units damaged in the accident and released radionuclides, most of which were not relevant to their study. Then, the author delved into unrelated previous studies, leading to confusion. Furthermore, their findings (NOT settings) in the experiments were antecedently shown in the last part of this section. I propose that the authors should simply answer the following key questions; why and for what purpose did the authors selected the study site and the monitoring period? What is the height of the aerosol sampler installation? What is the scientific significance to determine the source of 137Cs-bearing particles? At this stage, unfortunately this manuscript is too descriptive and looks like a summary of technical reports.
Specific comments and technical corrections
The inaccuracies in this manuscript are so numerous that I cannot list all of them within the review period.
Citation: https://doi.org/10.5194/egusphere-2023-2999-RC1 - AC1: 'Reply on RC1', Peng Tang, 23 Feb 2024
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RC2: 'Comment on egusphere-2023-2999', Anonymous Referee #2, 28 Feb 2024
The authors Li et al. present an analysis of high-volume aerosol samples obtained during field sampling in Fukushima Prefecture and relate particle analysis to variations in filter-collected concentrations of the radoinuclide 137Cs with a focus on identifying 137Cs sources. The manuscript is moderately well-written and presents some interesting observations on potential mechanisms by which 137Cs may be reentering the atmosphere. However, I do not believe the analysis is sufficiently complete to quantitatively discern the aerosol types that act as 137Cs carriers, as the authors purport. In its current form, I do not believe the manuscript meets the high bar for publication in ACP.
The authors focus their analysis on the months of May and September due to higher measured 137Cs concentrations and draw conclusions on 137Cs carriers based on particles observed during these times. However, without any analysis of particle types and composition during similar months that have low 137Cs concentrations (March-April, July-August), it is not demonstrated whether the particles observed during May and September are fundamentally different from those observed at other times. Are dust and different types of biological particles not generated during March-April and July-August? Or are there other factors that lead to different 137Cs concentrations across different months?
In Figure 10, the authors use a normalized number of particles, but the methodology for this normalizing is not clearly explained. Related to this, the authors present no data on the overall number, volume, or mass of particles sampled across the different sampling periods. Could the 137Cs concentration differences between May and September and the other months simply be due to different number, volume, or mass of particles sampled?
The authors use a regression analysis to estimate 137Cs concentrations in their samples, shown in Figure 12. In contrast to the author's conclusions, this estimate suggests to me that the sources of 137Cs are not completely understood, based on the overall poor agreement (50% of samples show substantial disagreement) and the fact that the differences could be either positive or negative for different samples.
The authors note in Section 2.3 that wind direction was measured at the site, but this was not used in any of the analysis. Does wind direction provide any insight into the 137Cs concentrations across different months or inform any of the other correlations that are observed and discussed by the authors? The authors also discuss a negative correlation between precipitation and 137Cs in Tables 7 and 8, which would appear to suggest that particle washout is more significant than particle generation processes that are stimulated by precipitation. The implications of this negative correlation are not discussed at all in the text. I also wonder whether analysis of the meteorological data at smaller timescales may provide more clear insight into higher or lower 137Cs concentrations for different samples.
Lastly, although May and September have higher 137Cs concentrations, each month has a single sample with substantially higher 137Cs than the rest of the samples. Can either particle analysis or meteorological data for these individual samples provide any insight into their high 137Cs concentrations relative to the rest of the month or provide any insight on 137Cs sources? Are there any other processes (for example, differences in remediation activities) that might be influencing the monthly trends?
Technical note: particles with diameter less than 1 um are often referred to as "PM1" or as a subset of fine PM (<2.5 um) and this type of technical terminology should be used in place of "little particles."
Citation: https://doi.org/10.5194/egusphere-2023-2999-RC2 -
AC2: 'Reply on RC2', Peng Tang, 09 Mar 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2023-2999/egusphere-2023-2999-AC2-supplement.zip
-
AC2: 'Reply on RC2', Peng Tang, 09 Mar 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-2999', Anonymous Referee #1, 06 Feb 2024
General comments
In this manuscript, there are three critical flaws, hindering publication.
Firstly, the authors did not directly measure 137Cs concentration of the aerosol samples, resulting in overinterpretation. Although they measured 137Cs concentration in the atmosphere during the observed period and compared it with the number and/or type of particles trapped in the filter, this evidence seems insufficient and indirect for identifying the source of the particles. Why not use imaging plates, as suggested by Tang et al. (2022) and Igarashi et al. (2019a), which were cited in the manuscript. Furthermore, I could not understand how the authors detected and counted each particle in a quantitative way. For example, how many particles were identified in the 12-mm diameter sections from the middle or edge area of the aerosol filter? How were areas for microscope images selected? More detailed raw data should be show, as demonstrated by Igarashi et al. (2019b) and their supplementary files.
The second flaw is the absence of basic scientific data. The abstract and conclusion stated that the authors continued monitoring from January to September and discussed seasonal variations in 137Cs-bearing aerosol samples. However, this study was actually a snapshot―they collected aerosol samples only in few days only in April, May and September, as shown in Table 2. I could not recognize the meaning of their excuse of “The absent samples in late May and early September 2019 were ascribed to the sampling plan and summer vacation.” (L. 115–116). Were data for monitoring periods not listed in this table taken from other references? In addition, in Figure 2 and 3, I found that horizontal axes of line graphs were not continuous and there are unexplained break axes. This is totally inaccurate in research.
The third flaw is that the objective of this manuscript was unclear. The introduction section was scattered in several directions. Its starts with general information on reactor units damaged in the accident and released radionuclides, most of which were not relevant to their study. Then, the author delved into unrelated previous studies, leading to confusion. Furthermore, their findings (NOT settings) in the experiments were antecedently shown in the last part of this section. I propose that the authors should simply answer the following key questions; why and for what purpose did the authors selected the study site and the monitoring period? What is the height of the aerosol sampler installation? What is the scientific significance to determine the source of 137Cs-bearing particles? At this stage, unfortunately this manuscript is too descriptive and looks like a summary of technical reports.
Specific comments and technical corrections
The inaccuracies in this manuscript are so numerous that I cannot list all of them within the review period.
Citation: https://doi.org/10.5194/egusphere-2023-2999-RC1 - AC1: 'Reply on RC1', Peng Tang, 23 Feb 2024
-
RC2: 'Comment on egusphere-2023-2999', Anonymous Referee #2, 28 Feb 2024
The authors Li et al. present an analysis of high-volume aerosol samples obtained during field sampling in Fukushima Prefecture and relate particle analysis to variations in filter-collected concentrations of the radoinuclide 137Cs with a focus on identifying 137Cs sources. The manuscript is moderately well-written and presents some interesting observations on potential mechanisms by which 137Cs may be reentering the atmosphere. However, I do not believe the analysis is sufficiently complete to quantitatively discern the aerosol types that act as 137Cs carriers, as the authors purport. In its current form, I do not believe the manuscript meets the high bar for publication in ACP.
The authors focus their analysis on the months of May and September due to higher measured 137Cs concentrations and draw conclusions on 137Cs carriers based on particles observed during these times. However, without any analysis of particle types and composition during similar months that have low 137Cs concentrations (March-April, July-August), it is not demonstrated whether the particles observed during May and September are fundamentally different from those observed at other times. Are dust and different types of biological particles not generated during March-April and July-August? Or are there other factors that lead to different 137Cs concentrations across different months?
In Figure 10, the authors use a normalized number of particles, but the methodology for this normalizing is not clearly explained. Related to this, the authors present no data on the overall number, volume, or mass of particles sampled across the different sampling periods. Could the 137Cs concentration differences between May and September and the other months simply be due to different number, volume, or mass of particles sampled?
The authors use a regression analysis to estimate 137Cs concentrations in their samples, shown in Figure 12. In contrast to the author's conclusions, this estimate suggests to me that the sources of 137Cs are not completely understood, based on the overall poor agreement (50% of samples show substantial disagreement) and the fact that the differences could be either positive or negative for different samples.
The authors note in Section 2.3 that wind direction was measured at the site, but this was not used in any of the analysis. Does wind direction provide any insight into the 137Cs concentrations across different months or inform any of the other correlations that are observed and discussed by the authors? The authors also discuss a negative correlation between precipitation and 137Cs in Tables 7 and 8, which would appear to suggest that particle washout is more significant than particle generation processes that are stimulated by precipitation. The implications of this negative correlation are not discussed at all in the text. I also wonder whether analysis of the meteorological data at smaller timescales may provide more clear insight into higher or lower 137Cs concentrations for different samples.
Lastly, although May and September have higher 137Cs concentrations, each month has a single sample with substantially higher 137Cs than the rest of the samples. Can either particle analysis or meteorological data for these individual samples provide any insight into their high 137Cs concentrations relative to the rest of the month or provide any insight on 137Cs sources? Are there any other processes (for example, differences in remediation activities) that might be influencing the monthly trends?
Technical note: particles with diameter less than 1 um are often referred to as "PM1" or as a subset of fine PM (<2.5 um) and this type of technical terminology should be used in place of "little particles."
Citation: https://doi.org/10.5194/egusphere-2023-2999-RC2 -
AC2: 'Reply on RC2', Peng Tang, 09 Mar 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2023-2999/egusphere-2023-2999-AC2-supplement.zip
-
AC2: 'Reply on RC2', Peng Tang, 09 Mar 2024
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