폴리에틸렌 미세플라스틱과 중금속의 복합독성 및 독성 상호작용 평가 = Evaluation of Combined Toxicity and Toxic Interactions between Polyethylene Microplastics and Heavy Metals

다국어 초록 (Multilingual Abstract)

Microplastics and heavy metals frequently coexist in aquatic environments, and their combined toxicity may be altered by environmental weathering of plastic particles. This study evaluated the combined toxicity and toxicity interaction patterns of non-weathered polyethylene microplastics （NPE） and UV-weathered polyethylene microplastics （UVPE） with Cr （VI）, Cd （II）, Hg （II）, and a mixed-metal system using sulfur-oxidizing bacteria （SOB）. Toxic responses were assessed using electrical conductivity （EC）-based functional inhibition, independent action （IA） based interaction analysis, response surface methodology （RSM）, and superoxide dismutase （SOD） inhibition as an oxidative stress-related endpoint. Surface characterization using SEM and ATR-FTIR showed that UV treatment induced clear morphological and chemical changes in polyethylene microplastics, including increased surface roughness, cracks, surface delamination, and an increase in the carbonyl index. These results confirmed that the applied UV treatment produced detectable weathering-related alterations in particle properties. RSM analysis demonstrated that the effects of weathering differed depending on the metal type. Under Cr （VI） exposure, the inhibition surface shifted upward after weathering, and the high-inhibition region expanded toward lower and intermediate concentration ranges. In the Cd （II） system, inhibition responses remained largely linear, whereas the interaction response under UVPE showed a significant quadratic
pattern, indicating that weathering changed the overall interaction structure. In the Hg （II） system, UVPE substantially increased EC inhibition, while IA-based interaction patterns differed between NPE and UVPE. In the mixed-metal system, antagonism was dominant under both NPE and UVPE conditions, although the magnitude and spatial distribution of interaction were modified by weathering. SOD inhibition showed a significant positive correlation with EC inhibition across all treatments, and this relationship was more distinct in the UVPE group. However, the explanatory power was limited, indicating that SOD alone did not fully explain EC-based functional inhibition. Overall, this study demonstrates that UV weathered polyethylene microplastics can alter not only the magnitude of combined toxicity but also the direction and spatial distribution of toxicity interactions with heavy metals in an SOB-based test system. These findings suggest that weathered microplastics should be considered dynamic factors in combined ecological risk assessment.

목차 (Table of Contents)

• Ⅰ. 서 론 1
• Ⅱ. 연 구 사 6
• III. 재료 및 방법 29
• 3.1재료 29
• 3.1.1 미세플라스틱 및 중금속 시약 29
• 3.1.2 중금속 stock solution 제조 30
• 3.1.3 SOB 배양 및 시험계 구성 30
• 3.2시험 방법 33
• 3.2.1 미세플라스틱 UV 풍화 처리 33
• 3.2.2 미세플라스틱 표면 특성 분석 35
• 3.2.3 단일 독성 시험 37
• 3.2.4 복합 독성 시험 38
• 3.2.5 산화스트레스 지표（SOD） 측정 42
• 3.3 분석 방법 44
• 3.3.1 단일 독성 Dose-response fitting 및 EC50 산정 44
• 3.3.2 복합 독성의 상호작용 평가 44
• 3.3.3 반응표면 적합 및 시각화 46
• 3.3.4 통계분석 47
• Ⅳ. 결과 및 고찰 48
• 4.1 미세플라스틱의 표면 변화 분석 48
• 4.2개별 독성 측정 결과 53
• 4.3 복합 독성 측정 결과（Inhibition, Interaction） 60
• 4.3.1 Cr（VI） 61
• 4.3.2 Cd（II） 70
• 4.3.3 Hg（II） 78
• 4.3.4 Mixture 88
• 4.4 SOD 측정 결과 97
• Ⅴ. 결 론 107
• 참 고 문 헌 111