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정성현(Sung Hyun Jung),서일원(Il Won Seo),박선구(Sunku Park),이효영(Hyoyoung Lee),김병욱(Byunguk Kim) 한국방재학회 2022 한국방재학회논문집 Vol.22 No.6
최근 해양 및 담수 수계로 유입되는 플라스틱의 양이 급격하게 증가함에 따라서 미세플라스틱(micro-plastics)이 수생태계에 미치는 영향에 대한 연구가 활발하게 수행되고 있다. 수계 내에 유입된 미세플라스틱 입자의 이송 및 확산 거동에 대한 수치 모의와 생태학적 영향 평가를 위해서는 침강속도(settling velocity)특성 규명이 우선적으로 필요하다. 일반적으로 미세플라스틱 입자의 침강거동을 유사 입자(sediment particle)와 유사한 거동을 보인다고 가정하고 있으나, 밀도와 형상 특성이 상이한 미세플라스틱 입자를 대상으로 충분한 실험 및 검증이 수행되지 못했다. 따라서 본 연구에서는 다양한 입경과 밀도를 갖는 구형 미세플라스틱 입자에 대해 입자추적기법을 적용하여 침강 실험을 수행하고, 새로운 침강속도 식의 보정 계수를 제안하였다. 실험결과 층류 영역에서는 Stokes의 관계식과 같은 침강속도와 무차원 입자 직경간에 명확한 선형 관계를 갖는 것으로 나타났으나, 천이 영역에서는 비선형관계로 변화하는 것으로 밝혀졌다. 이러한 천이 영역에서의 비선형성은 항력계수와 입자 레이놀즈수의 관계에서도 명확하게 드러났다. 측정결과를 바탕으로 선행연구에서 제안된 침강속도 경험식의 적용성을 분석한 결과, 유사 입자 기반 경험식들의 경우 20% 이상의 상대 오차를 나타냈다. 본 연구에서 회귀분석을 통해 새롭게 도출된 침강속도 식의 보정 계수를 적용할 경우 기존 유사 입자 연구에서 제안된 경험식들보다 더 높은 예측 정확도를 갖는 것으로 나타났다. Research on the effects of microplastics on water environments is being widely conducted because the discharge of microplastics into the ocean and freshwater systems is rapidly increasing. For the numerical simulation of the transport and diffusion of microplastics introduced into water systems and evaluation of the ecological impacts, the settling velocities of microplastics must be investigated first. The settling behavior of microplastics has been commonly assumed to be similar to that of sediment particles, but this has not been sufficiently verified for various types of microplastic. In this study, a laboratory experiment was performed to measure the settling velocities of spherical microplastic particles in freshwater using a particle tracking technique, and a new calibration coefficient of the settling velocity was proposed based on the experimental data. The experimental results showed a clear linear relationship between the settling velocity and dimensionless particle diameter in the laminar flow region, as suggested by Stokes' law. However, the settling velocities in the transition region had a nonlinear relationship, which was also clearly demonstrated in the relationship between the drag coefficient and the particle Reynolds number. The evaluation of the existing equations for settling velocity showed that previous empirical equations based on experiments on sediment particles produced relative errors of 20% or more. However, the proposed calibration coefficient provided a more accurate prediction of the settling velocities of microplastic particles than the existing empirical equations based on sediment studies.
Study on the Emerging VOCs Analysis Method using Purge&Trap GC/MS in Raw Water and Treated Water
Sowon Kang(강소원),Hyunseung Cho(조현승),Taekkyun Choi(최택균),Sunku Park(박선구),Hakseok Kim(김학석),Sangrak Lee(이상락),Juhyun Park(박주현) 환경독성보건학회 2021 한국독성학회 심포지움 및 학술발표회 Vol.2021 No.5
Volatile Organic Compounds (VOCs) are unsaturated hydrocarbons that cause odors and ozone through volatilization into the atmosphere. In this study, the analysis method of VOCs was performed using Purge & Trap gas chromatography/mass spectrometry. Analysis method was discussed and optimized. The results of 14 VOCs have shown that Method Detection Limit (MDL) was in the range from 0.0098 μg/L to 0.6519 μg/L and Limit of Quantification (LOQ) was in the range from 0.0313 μg/L to 2.0762 μg/L. The results of accuracy and precision ranged from 85.9 % to 114.8 % and 1.0 % to 3.3 %. Investigation of the matrix effects on tap water has shown that this method is suitable for VOCs analysis. Raw water and treated water of 15 water treatment plants were studied by developed method. As a results, Chloromethane was detected in the range from N/D to 1.924 μg/L of raw water and in the range from N/D to 4.595 μg/L of treated water. Detection frequency was 50.0 % of raw water and 86.6 % of treated water. In the case of Chloromethane in raw water, the frequency of detection was decreased during the period of wet season. In addition, in the case of water treatment plant that does not use a coagulant or uses river-side filtered water, the formation of chloromethane was less in treated water. These results are intended to be used as scientific basis data for the preparation of the water quality environment policy system in the future.