College of Environment and Ecology, Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of education, Chongqing University, Chongqing 400045, China.
College of Environment and Ecology, Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of education, Chongqing University, Chongqing 400045, China.
J Hazard Mater. 2023 Feb 5;443(Pt B):130310. doi: 10.1016/j.jhazmat.2022.130310. Epub 2022 Nov 2.
Riparian sediment is the last barrier preventing contaminants from polluting aquatic ecosystems. Recently, microplastics (MPs) have frequently been found in sediments. However, the MP aging process and its impact on sediments remain unknown. This study aimed to identify the key driving factors and mechanisms of riparian sediment on MPs aging behavior. The results showed that MPs surface suffered heavy breakage and the oxygen-to-carbon ratio of MPs increased by 268 % after accumulation in sediment for 214 d. The carbonyl index revealed that the degree of MP aging driven by dissolved organic matter (DOM) was 6.7-83.6 % greater than that of colloids, indicating that DOM was the key sediment fraction driving MP aging. Sunlight was an important environmental factor that enhanced MPs aging by sediment fractions, because photo-irradiated DOM produced hydroxyl and superoxide radicals to damage the MPs structure. Benzoic acid, dibenzoylmethane, and 4-heptyl-4,6-diphenyl-tetrahydro-pytan-2-one were the main products during the MP aging process under the interaction of sunlight and DOM, which showed acute toxicity to aquatic organisms and caused more severe toxicity during the chronic period. These results clearly clarify the behavior and environmental risk of MPs after accumulation in sediment, providing guide information to control MP pollution in the riparian zone.
河岸沉积物是防止污染物污染水生生态系统的最后一道屏障。最近，沉积物中经常发现微塑料（MPs）。然而，MP 的老化过程及其对沉积物的影响尚不清楚。本研究旨在确定河岸沉积物对 MPs 老化行为的关键驱动因素和机制。结果表明，MPs 表面受到严重破坏，在沉积物中积累 214 天后，MPs 的氧碳比增加了 268%。羰基指数表明，溶解有机质（DOM）驱动 MP 老化的程度比胶体高 6.7-83.6%，表明 DOM 是驱动 MP 老化的关键沉积物。阳光是增强 MPs 老化的重要环境因素，因为光辐照的 DOM 产生羟基和超氧自由基破坏 MPs 结构。在阳光和 DOM 的相互作用下，苯甲酸、二苯甲酰甲烷和 4-庚基-4,6-二苯基-四氢-吡喃-2-酮是 MPs 老化过程中的主要产物，它们对水生生物具有急性毒性，并在慢性期间造成更严重的毒性。这些结果清楚地阐明了 MPs 在沉积物中积累后的行为和环境风险，为控制河岸带的 MP 污染提供了指导信息。
