영산강수계 의료기원 방사성요오드(¹³¹I) 핵종의 분포 및 거동평가 = The Distribution and Behavior of Medically-derived ¹³¹I in the Yeongsan River Basin

다국어 초록 (Multilingual Abstract)

BACKGROUND: Recently, the use of ¹³¹I for diagnosis and treatment of thyroid cancer has been increasing, and the radionuclide is continuously released into aquatic ecosystem. This study was carried out to investigate the ¹³¹I concentrations in mainstreams, tributaries, and sewage wastewater treatment plants (SWTPs) of the Yeongsan River Basin and to identify their origins from the assessment of behaviors in the rivers.
METHODS AND RESULTS: The water samples were collected from 19 sites including mainstreams (13), tributaries (4) and SWTPs (2). The ¹³¹I concentration was measured using a gamma-ray spectrometry with a HPGe detector. The ¹³¹I in SWTPs was detected mostly in the discharged effluent at the sampling sites. However, from the surface water of the rivers, ¹³¹I was found only at two sites from each sampling period of the first (MS4 and MS10) and the second half (MS4 and MS7) of the year 2017. The concentrations of ¹³¹I in the effluent discharged from SWTPs were in the range of 0.0870 to 3.87 Bq/L for SWTP1, and <MDC to 0.534 Bq/L for SWTP2. The concentrations of the isotope detected in surface water of the rivers were between 0.0908 to 0.174 Bq/L. The behavior assessment of ¹³¹I in the river revealed that it was not detected in the upper streams of the mainstreams and tributaries, while continuous detection was found in the SWTPs and downstream sites affected by the effluent. However, the concentration of ¹³¹I decreased downstream, eventually becoming undetectable. Such behavior was closely related to the behavior found in the SWTPs.
CONCLUSION: These results indicated that medicallyderived ¹³¹I was discharged to the river via sewage effluent at the SWTPs. It is necessary to evaluate the influence of aquatic ecosystems through continuous monitoring in the future.