水体中微塑料对重金属汞的吸附行为及其对涡虫的毒性效应

Adsorption Behavior of Microplastics on Heavy Metal Mercury in Water and Its Toxic Effects on Planarians

环境中的微塑料(MPs)污染日益增加,已经成为备受关注的全球环境问题。已有研究表明,微塑料通过自身的物理效应和吸附作用,能够吸附重金属等污染物,产生“特洛伊木马效应”。因此,微塑料与重金属之间的相互作用在风险评估中具有特殊且重要的意义。以聚苯乙烯(PS)为例,选用东亚三角涡虫作为实验动物,探究微塑料吸附重金属汞(Hg)后的生物效应和毒性机制。采用红外光谱、扫描电子显微镜、动态光散射分析对PS-MPs及PS-Hg^(2+)进行详细表征。急性毒性实验表明,Hg^(2+)对整体涡虫的半数致死浓度(LC_(50))值为0.13 mg/L,对再生涡虫的LC_(50)值为0.12 mg/L。Hg^(2+)能够在涡虫体内富集,并产生毒性效应,导致涡虫死亡和胚基生长的抑制。此外,结合同步辐射X射线荧光光谱成像(XRF)和原子荧光光谱仪(AFS)分析技术,发现PS-MPs会增强Hg^(2+)在涡虫体内的富集和毒性。通过组织学分析、原位杂交、免疫荧光及测定SOD、MDA、ATP含量、ATP合酶和GPX4活性、线粒体膜电位及线粒体中Fe^(2+)的相对水平和总Fe含量,发现Hg^(2+)会引起涡虫组织学损伤,影响涡虫体内Neoblasts的维持与增殖,引起涡虫抗氧化防御系统的紊乱、细胞损伤和线粒体功能的破坏,而PS-MPs的引入会加剧这些现象。综上所述,PS-MPs与Hg^(2+)具有联合作用,PS-MPs的加入能够增强Hg^(2+)的毒性,扰乱涡虫的稳态。因此,应重视微塑料与重金属的联合作用,并从多方面进行污染物的风险评估。

Microplastic(MPs)pollution in the environment has been increased rapidly and become a global environmental problem of concern.Studies have shown that microplastics(MPs)can adsorb heavy metals through physical effects and adsorption,leading to a“Trojan horse effect”.Therefore,understanding the interaction between MPs and heavy metals is crucial for risk assessment.In this study,polystyrene(PS)was used to investigate the biological effects and toxicity mechanism of MPs after adsorption of mercury(Hg)using Dugesia japonica as test organism.Infrared spectroscopy,scanning electron microscopy and dynamic light scattering analysis were employed to characterize the PS-MPs and PS-Hg^(2+).The acute toxicity test revealed that the Lethal concentration 50(LC_(50))of Hg^(2+)was 0.13 mg/L for the homeostatic planarians and 0.12 mg/L for the regeneration planarians.Hg^(2+)accumulated in planarians and produced toxic effects,resulting in the death and the inhibition of planarian growth.Additionally,the presence of PS-MPs enhanced the accumulation and toxicity of Hg^(2+).Combined synchrotron radiation X-ray fluorescence spectroscopy(XRF)and atomic fluorescence spectroscopy(AFS)analysis techniques,the introduction of PS-MPs enhanced the enrichment and toxicity of Hg^(2+)in planarian bodies.Through histological assay,whole-mount in situ hybridization,whole-mount immunofluorescence,and measurements of SOD,MDA,ATP content,ATPase and GPX4 activities,mitochondrial membrane potential,the relative level of Fe^(2+) in mitochondria and the total Fe content,it was found that Hg^(2+)induced histological damage,affected the maintenance and proliferation of neoblasts,disrupted the antioxidant defense system,caused cell damage and impaired mitochondrial function in planarians,and the introduction of PS-MPs exacerbated these effects.These results indicate that PS-MPs has a synergistic effect with Hg^(2+),enhancing its toxicity of Hg^(2+)and disrupting planarians homeostasis.Therefore,attention should be paid to the combined effects of MPs and heavy metals and the comprehensive risk assessments should be carried out.