Radioactivity in surface water
Analyzing radioactive materials in surface waters provides information on their time behaviour. Samples taken from different bodies of water indicate the geographic variation of radionuclides.
Starting from 2024, the Kokemäenjoki and Oulujoki samples will be examined four times a year, and the Kymijoki and Kemijoki samples will be examined once a year, in spring or in autumn (Figure 6.1). In 2024, annual samples were taken in the spring. Strontium was no longer analysed in the 2024 samples.
The uneven regional distribution of Chernobyl fallout is still reflected in surface water results for 137Cs. Unlike Chernobyl fallout, the fallout from nuclear weapon tests was nearly evenly distributed in Finland, and its traces are still observed in the river water from northern Finland. Before the fallout from Chernobyl, concentrations of 137Cs were fairly even, but after 1986, the situation changed and caesium concentrations in surface water increased, but the concentrations have gradually fallen close to the situation before the Chernobyl accident. The highest concentrations of 137Cs are observed in samples in the Kymijoki catchment area, whose concentrations were approximately 3–10 orders higher than in surface water samples from other sources
The radioactivity levels of Cs-137 and Sr-90 in surface water samples in 2024 (Bq/m3)
River | Reference day | Cs-137 (Bq/m3) |
---|---|---|
Kymijoki | 11.3.2024 | 11 |
6.5.2024 | 11 | |
8.8.2024 | 13 | |
5.11.2024 | 12 | |
Kokemäenjoki | 15.5.2024 | 4,0 |
Oulujoki | 27.3.2024 | 2,5 |
29.5.2024 | 8,9 | |
9.9.2024 | 2,4 | |
4.11.2024 | 1,9 | |
Kemijoki | 23.4.2024 | 2,0 |
The radioactivity levels of Cs-137 and Sr-90 in surface water samples in 2023 (Bq/m3)
River | Reference day | Cs-137 (Bq/m3) | Sr-90 (Bq/m3) |
---|---|---|---|
Kymijoki | 9.10.2023 | 14,2 | 4,3 |
Kokemäenjoki | 18.9.2023 | 4,5 | 3,9 |
Oulujoki | 26.9.2023 | 2,7 | 2,5 |
Kemijoki | 10.10.2023 | 1,2 | 2,1 |
The radioactivity levels of Cs-137 and Sr-90 in surface water samples in 2022 (Bq/m3)
River | Reference day | Cs-137 (Bq/m3) | Sr-90 (Bq/m3) |
---|---|---|---|
Kymijoki | 10.5.2022 | 10,7 ± 1,2 | 3,7 ± 0,4 |
Kokemäenjoki | 20.6.2022 | 5,3 ± 0,6 | 3,7 ± 0,4 |
Oulujoki | 16.5.2022 | 1,9 ± 0,3 | 2,4 ± 0,3 |
Kemijoki | 24.5.2022 | 1,1 ± 0,3 | 1,2 ± 0,2 |
The radioactivity levels of Cs-137 and Sr-90 in surface water samples in 2021 (Bq/m3)
River | Reference day | Cs-137 (Bq/m3) | Sr-90 (Bq/m3) |
---|---|---|---|
Kymijoki | 7.9.2021 | 16 ± 2 | 4,6 ± 0,5 |
Kokemäenjoki | 7.10.2021 | 3,8 ± 0,6 | 3,8 ± 0,4 |
Oulujoki | 6.9.2021 | 2,5 ± 0,5 | 2,4 ± 0,3 |
Kemijoki | 6.9.2021 | 1,0 ± 0,2 | 1,5 ± 0,2 |