2:45 PM - 3:00 PM
[AGE34-05] CsMPs vertical distribution in forest soils and their runoff throgh the river during rainfall events
★Invited Papers
Keywords:Fukushima, Radiocesium, CsMPs
Introduction
CsMPs are insoluble glassy particles derived from the Fukushima Daiichi Nuclear Power Plant accident. CsMPs might increase radioactive cesium (RCs) concentration of soil and water. However, there are a few previous studies to focus on the migration and distribution of CsMPs in the environment. In this presentation, we would like to show our previous studies focusing on distribution of CsMPs in the soil and their migration through rivers during rainfall event.
Materials and Methods
1)The vertical distribution of CsMPs in the soil
Soil column samples were collected from multiple sites located in contaminated forest areas in Fukushima Prefecture between 2022 and 2023. The column was divided into soil layers with a specific depth, and the RCs concentration and that derived from CsMPs (CsMPs concentration) of each soil layer were measured. CsMPs were identified from thinly spread soil samples using an imaging plate with reference to the QCP method.
2) CsMPs discharge through rivers in the watersheds with different contamination condition
In order to understand the migration of CsMPs due to water erosion during rainfall event, we investigated their discharge in two watersheds with different contamination condition. Water samples were collected using an automatic water sampler during rainfall event. Furthermore, we collected water samples using a tank of 20 L even when there was no rainfall event. The collected water samples were separated into suspended solids and filtrate using a membrane filter with a porosity 0.45 µm, and the RCs concentration in each was measured (particulate and dissolved RCs). For particulate RCs, CsMPs was identified as in the case of soil sample. Furthermore, we compared the solid-liquid distribution coefficient in the river water and that without the CsMPs.
Results and discussions
1) CsMPs might be distributed in the soil surface layer. This result suggested that CsMPs might be easily mobile due to soil erosion. Some CsMPs were detected in deeper soil layers, which might be due to their migration as colloids or due to bioturbation.
2) CsMPs were detected only in the samples collected during rainfall event. This result indicate that CsMPs might enter the river due to soil erosion. When only samples containing CsMPs were evaluated, the proportion of CsMPs to particulate RCs was more than 50% in the river located in the less contaminated condition. Furthermore, the apparent distribution coefficient was twice as the net coefficient without CsMPs contribution, which suggested that CsMPs might cause the over estimation in the river water. In the less contaminated area, CsMPs might be one of the factors to cause local increases in particulate RCs and distribution coefficient.
CsMPs are insoluble glassy particles derived from the Fukushima Daiichi Nuclear Power Plant accident. CsMPs might increase radioactive cesium (RCs) concentration of soil and water. However, there are a few previous studies to focus on the migration and distribution of CsMPs in the environment. In this presentation, we would like to show our previous studies focusing on distribution of CsMPs in the soil and their migration through rivers during rainfall event.
Materials and Methods
1)The vertical distribution of CsMPs in the soil
Soil column samples were collected from multiple sites located in contaminated forest areas in Fukushima Prefecture between 2022 and 2023. The column was divided into soil layers with a specific depth, and the RCs concentration and that derived from CsMPs (CsMPs concentration) of each soil layer were measured. CsMPs were identified from thinly spread soil samples using an imaging plate with reference to the QCP method.
2) CsMPs discharge through rivers in the watersheds with different contamination condition
In order to understand the migration of CsMPs due to water erosion during rainfall event, we investigated their discharge in two watersheds with different contamination condition. Water samples were collected using an automatic water sampler during rainfall event. Furthermore, we collected water samples using a tank of 20 L even when there was no rainfall event. The collected water samples were separated into suspended solids and filtrate using a membrane filter with a porosity 0.45 µm, and the RCs concentration in each was measured (particulate and dissolved RCs). For particulate RCs, CsMPs was identified as in the case of soil sample. Furthermore, we compared the solid-liquid distribution coefficient in the river water and that without the CsMPs.
Results and discussions
1) CsMPs might be distributed in the soil surface layer. This result suggested that CsMPs might be easily mobile due to soil erosion. Some CsMPs were detected in deeper soil layers, which might be due to their migration as colloids or due to bioturbation.
2) CsMPs were detected only in the samples collected during rainfall event. This result indicate that CsMPs might enter the river due to soil erosion. When only samples containing CsMPs were evaluated, the proportion of CsMPs to particulate RCs was more than 50% in the river located in the less contaminated condition. Furthermore, the apparent distribution coefficient was twice as the net coefficient without CsMPs contribution, which suggested that CsMPs might cause the over estimation in the river water. In the less contaminated area, CsMPs might be one of the factors to cause local increases in particulate RCs and distribution coefficient.