Strontium-90 levels in seawater southeast of Jeju Island during 2021-2023.

This study introduces an efficient method for determining 90Sr activity levels in seawater, reducing the processing time to <3 h for 50 L of seawater. The key feature of the proposed method is the chemical separation of 90Y when it is in equilibrium with 90Sr, which is achieved by utilizing custom-made sample-loading equipment and an automated radionuclide separation instrument. As a result, the procedure consistently yields a recovery rate > 90 % for 90Y. Investigations of 90Sr levels were conducted in the ocean southeast of Jeju Island from November 2021 to January 2023. Owing to the regional ocean circulation, this region was among the first within the Korean Peninsula to experience the impact of the Fukushima-accident-derived radionuclides. Throughout the investigation period, the observed 90Sr activity concentration ranged from 0.57 to 1.0 Bq m-3. No distinct temporal variation of 90Sr was observed in the selected area during the investigation.

Automated extraction chromatographic radionuclide separation system for analysis of 90Sr in seawater.

After the Fukushima Dai-ichi nuclear power plant disaster, the demand for a rapid method for the detection of environmental radioactivity increased drastically. Since the development of extraction chromatography using resins, analytical methods have advanced significantly in terms of simplicity and required labor. Herein, a home-made automated separation system that is applicable radio-extraction chromatographic separation techniques is reported. A simple, rapid, and high-throughput method was developed using this home-made automated separation system to analyze radiostrontium in seawater in emergency and routine situations. For emergency situations, radiostrontium in seawater is pre-concentrated on a cation exchange resin and consecutively purified using the Sr-resin. Fifty minutes are required for the purification of 90Sr in four samples (100 ml). The minimum detectable activity (MDA) for 90Sr is 0.2 Bq kg-1 at 100 min counting, with a recovery of 70% and counting efficiency of 95% in the scintillation mode. For routine monitoring, 90Y that is in equilibrium with 90Sr is first separated from the sample matrix using DGA. Treatment of 30 L of each seawater sample requires ~2 h. The MDA for this method is 0.3 mBq kg-1 at 400 min counting with a recovery of 70% and counting efficiency of 67% in the Cerenkov mode. By employing the developed method, the measured 90Sr in seawater collected from the coastal area of Korea is 0.92 ± 0.18 mBq kg-1, which is comparable to that reported previously. The measurements were obtained using a liquid scintillation counter, and the entire separation process was performed by employing the home-made separation system.

Design and performance of an automated radionuclide separator: its application on the determination of 99Tc in groundwater.

A modular automated radionuclide separator for (99)Tc (MARS Tc-99) has been developed for the rapid and reproducible separation of technetium in groundwater samples. The control software of MARS Tc-99 was developed in the LabView programming language. An automated radiochemical method for separating (99)Tc was developed and validated by the purification of (99m)Tc tracer solution eluted from a commercial (99)Mo/(99m)Tc generator. The chemical recovery and analytical time for this radiochemical method were found to be 96 ± 2% and 81 min, respectively.

Antimutagenic, antioxidant and free radical scavenging activity of ethyl acetate extracts from white, yellow and red onions.

The beneficial effects of red, yellow and white onion extracts have been assessed by antioxidant activity and antimutagenic activity. And the effects compared to BHT and ascorbic acid. Total phenolic compounds and flavonoids in onion extracts were determined. Yellow onion extract had more organic acid and free sugar than those detected in the white and red onion extract. The scavenging activity of DPPH radical and H(2)O(2) were increased depending on the concentration. The antioxidant activities using beta-carotene-linoleate system and reducing power were increased but the effect was small to that of BHT and ascorbic acid. After digested, extracts showed antimutagenic activities, and it seems that they inhibit the mutagenicity for digesting. This study demonstrated that the antimutagenicities and antioxidant properties of ethyl acetate extract against mutagens were related to their phenols and flavonoids, which are heat stable and losses digestive juices are relatively low.