FY2018 Results of the Radioactive Material Monitoring in the Water Environment March 2020 Ministry of the Environment Contents Outline .......................................................................................................................................................... 1 Part 1: National Radioactive Material Monitoring in the Water Environment throughout Japan (FY2018) . 6 1 Objective and Details ............................................................................................................................. 6 1.1 Objective .................................................................................................................................... 6 1.2 Details ........................................................................................................................................ 6 2 Survey Methods and Analysis Methods .............................................................................................. 19 2.1 Survey methods ....................................................................................................................... 19 2.2 Analysis methods ..................................................................................................................... 20 3 Results ................................................................................................................................................. 22 3.1 Detection of total β radioactivity and γ-ray emitting radionuclides .......................................... 22 (1) Public water areas .................................................................................................................. 22 1) Water ..................................................................................................................................... 22 2) Sediment ............................................................................................................................... 24 (2) Groundwater .......................................................................................................................... 26 3.2 Discussion regarding detected radionuclides .......................................................................... 28 (1) Detection of naturally occurring radionuclides ....................................................................... 28 1) Correlation between activity concentrations of K-40 in water samples and seawater ......... 28 2) K-40 in sediments ................................................................................................................. 30 3) Uranium and thorium series radionuclides in sediment samples ......................................... 31 (2) Detection of artificial radionuclides ........................................................................................ 34 1) Cs-134 and Cs-137 in water samples from public water areas ........................................... 34 2) Cs-134 and Cs-137 in sediment samples from public water areas ...................................... 35 3) Cs-134 and Cs-137 in groundwater ...................................................................................... 40 3.3 Survey results on seasonal variations ..................................................................................... 41 Part 2: Radioactive Material Monitoring in the Water Environment in and around Fukushima Prefecture (FY2018) ..................................................................................................................................................... 47 1 Objective and Details ........................................................................................................................... 47 1.1 Objective .................................................................................................................................. 47 1.2 Details ...................................................................................................................................... 47 2 Survey Methods and Analysis Methods .............................................................................................. 49 2.1 Survey methods ....................................................................................................................... 49 2.2 Analysis methods ..................................................................................................................... 49 3 Outlines of the Results ........................................................................................................................ 50 3.1 Detection of radioactive cesium ............................................................................................... 50 3.2 Detection of radionuclides other than radioactive cesium ....................................................... 53 4 Results ................................................................................................................................................. 54 4.1 Radioactive cesium .................................................................................................................. 54 i 4.1 -1 Water .................................................................................................................................... 54 (1) Public water areas .................................................................................................................. 54 1) Rivers .................................................................................................................................... 54 2) Lakes ..................................................................................................................................... 54 3) Coastal areas ........................................................................................................................ 54 (2) Groundwater .......................................................................................................................... 54 4.1-2 Sediment ............................................................................................................................... 58 (1) Detection status ..................................................................................................................... 58 1) Rivers .................................................................................................................................... 58 2) Lakes ..................................................................................................................................... 58 3) Coastal areas ........................................................................................................................ 58 (2) Changes in concentration levels ............................................................................................ 62 1) Rivers .................................................................................................................................... 62 2) Lakes ..................................................................................................................................... 63 3) Coastal areas ........................................................................................................................ 63 (3) Detection of radioactive materials in sediment by location .................................................... 64 1) Evaluation policy ................................................................................................................... 64 2) Concentration levels in sediment samples from rivers, lakes, and coastal areas and their changes by prefecture .......................................................................................................... 67 2)-1 Rivers ................................................................................................................................. 67 2)-2 Lakes ................................................................................................................................. 85 2)-3 Coastal areas ................................................................................................................... 101 2)-4 Conclusion ........................................................................................................................ 111 4.2 Results (Radionuclides other than radioactive cesium) ........................................................ 120 4.2-1 Radioactive strontium (Sr-90 and Sr-89) ............................................................................ 120 (1) Public water areas ................................................................................................................ 120 (2) Groundwater ........................................................................................................................ 123 4.2-2 Other γ-ray emitting radionuclides ...................................................................................... 124 Part 3: Other Radioactive Material Monitoring Conducted Nationwide (FY2018) ................................... 126 1 Outline of the Monitoring ................................................................................................................... 126 1.1 Covered monitoring ................................................................................................................ 126 1.2 Compilation methods ............................................................................................................. 126 2 Results 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