Radionuclide substances in the Japanese environment need to be monitored, after the contamination caused by the Fukushima Daiichi Nuclear Power station accident. In this study, we focused on the sampling methods used for sediments in lakes. We investigated radioactive concentrations of 134Cs and 137Cs in lakes sediments found in Fukushima prefecture using two types of sediment samplers, the grab and core sampler. The sampling points were the same as those used in the Lake Akimoto and Numasawa study of 2013. Thereafter, we compared that study's data with our grab and core samples. We obtained the concentration and type of radioactive Cs in the sediment with core samples and estimated the depth of the sediment samples with the grab sampler. The concentrations of Cs in the sediment samples taken with the grab samplers were underestimated, because the radioactive Cs was detected in the surface sediment samples using the core sediment sampler. Since appropriate sediment sampler selection is clearly important, we suggest using the core sampler for the sampling of particular radionuclides substances in the sediment.
We studied radioactivity dispersion caused by the nuclear accident at the Fukushima nuclear plant by analyzing the radioactivity of 33 moss samples belonging to five species. We focused on the fact that the ground coverage area of the moss carpet can be evaluated after sampling the moss so that a deposition rate in Bq/㎡ units is obtained. The moss proves to be much more sensitive to radioactive Cs-137 than the soil. We understand the analysis of the radioactivity in the moss is useful to draw a deposition map around the Fukushima nuclear power plant. Gamma rays from the radioactive Cs are measured using an NaI(Tl) scintillation counter. The influence of meteorological and geographical features is also reviewed using a radioactivity map, so that the local high level of radioactivity in Iitate-mura can be confirmed by an analysis of the mosses. The ratio of the radiation intensities of Cs-134 and Cs-137 in the moss measured with a CdZnTe detector was obtained for several mosses in several areas, finding no significant differences in their ratios.
In order to remove chloride ions for CODMn measurements, silver ions are required. However, no specific chloride ion assay is required. Therefore, we investigated a methodology that was simpler and easier than those conventionally used.The linear relationship between chloride ions and electrical conductivity has been confirmed statistically.However, environmental measurement certification business operators, who handle samples of different compositions, have doubts about the linearity of the results.We report that we were able to confirm linearity by using a sample with a neutral pH range and the process water removed and determine the assay of silver ions from measurements of electrical conductivity.