【作者】 张洁；

【导师】 申卫博；

【作者基本信息】 西北农林科技大学 ， 工程硕士（专业学位）， 2022， 硕士

【摘要】 微塑料（microplastics,MPs）和各种污染物在水环境中普遍存在,且不易降解。同时,作为载体,微塑料会通过吸附并携带有机及无机污染物,进一步将其输送到生物体体内,这可能会改变微塑料的环境行为、生物有效性以及潜在毒性,进而导致生态风险。到目前为止,大量研究表明微塑料对疏水性有机污染物有很强的吸附解吸作用,很少有报道揭示微塑料与无机污染物（重金属）以及亲水性污染物（染料）之间的相互作用。本研究选择传统微塑料聚乙烯（PE）和可降解微塑料聚乳酸（PLA）作为代表,将其在不同环境下老化,以重金属铅（Pb）和染料亚甲基蓝（MB）作为典型污染物,研究了老化前后微塑料对水环境中重金属以及有机染料之间的相互作用。主要结果如下:（1）三种老化方式（UV,O₃,UV/O₃）均对微塑料有一定的影响。其中,UV/O₃结合方式影响最为显著,在老化后的微塑料表面形成含氧官能团。因此选择此种方式进行微塑料老化实验。结果表明,UV/O₃老化处理显著提高了微塑料的含氧量、比表面积以及亲水性。微塑料老化后颜色均变黄,表面出现了明显的孔洞和裂缝,PE和PLA的Zeta电位分别从-5.1和-7.1降至-12.3和-9.5。相较于PE,UV/O₃老化后PLA的理化性质变化更大。（2）微塑料对重金属Pb（Ⅱ）和有机染料MB的吸附过程,用拟二级动力学模型和Langmuir模型拟合效果较好,说明微塑料对两种污染物的吸附是由物理吸附主导、化学吸附同时存在的多层吸附过程。老化微塑料对污染物的吸附量高于原始塑料,吸附性能依次为老化PLA>老化PE>原始PLA>原始PE。此外,吸附实验表明微塑料对重金属以及有机染料的吸附机制包括静电吸引、表面络合以及氢键作用。（3）微塑料对阳离子污染物的吸附还会受到周围环境的影响,其中p H的影响尤为明显。碱性溶液会增加吸附作用,p H增加,带负电荷的微塑料会通过静电相互作用增强对阳离子污染物的吸附。离子强度的增加导致微塑料对两种污染物的吸附能力降低,说明微塑料不仅与重金属发生相互作用,还与其它离子作用。（4）微塑料对污染物在模拟肠液中的解吸量大于在模拟淡水中的解吸量。此外,老化处理降低了微塑料对两种污染物的解吸率,表明老化微塑料对生物体的危害比原始微塑料更严重。因此,微塑料对生物体的潜在危害大于对水生环境的潜在危害,携带污染物的微塑料在摄入后可能会对水生生物产生不利影响。综上所述,微塑料在环境中的老化过程会影响其作为共存污染物的载体作用。研究结果对于了解微塑料的环境行为、提供微塑料对污染物的环境风险信息以及评估微塑料在环境中的实际作用具有重要意义。更多还原

【Abstract】 Microplastics（MPs）and various contaminants are prevalent in the aqueous environment and are hardly degraded.At the same time,as carriers,MPs can be further transported into organisms through the adsorption and carrying of organic and inorganic pollutants,which may alter the environmental behavior,bioavailability,and potential toxicity of MPs,leading to ecological risks.Several studies have shown that MPs have strong adsorption properties to hydrophobic organic pollutants in the environment,but few reports have revealed the interactions between MPs and inorganic pollutants（heavy metals）as well as hydrophilic pollutants（dyes）.In this study,traditional MPs polyethylene（PE）and degradable MPs polylactic acid（PLA）were selected as representatives.Its aging occurs in different environments,with heavy metal like lead（Pb）and the dye methylene blue（MB）as typical contaminants.And the interactions of microplastics to heavy metals as well as dyes in the aqueous environment before and after aged were investigated.The main results are as follows:（1）All three aging methods（UV,O₃,and UV/O₃）have certain effects on the MPs.Of these,the UV/O₃ combination has the most significant effect,with oxygen-containing functional groups appearing on the MPs’surface.Therefore,this method was chosen for the MPs aging experiments.The results showed that the UV/O₃ treatment significantly increased the oxygen content,specific surface area,and hydrophilicity of the MPs.After aging,the color of MPs turned yellow,and holes and cracks appeared on the surface.The Zeta potential of PE and PLA decreased from-5.1 and-7.1 to-12.3 and-9.5,respectively.Compared with PE,the physical and chemical properties of PLA changed more after UV/O₃ aging.（2）The adsorption process of heavy metal Pb（II）and organic dye MB by MPs were in accordance with the pseudo-second-order kinetic model and Langmuir model,indicating that the adsorption of the two pollutants by MPs was a multilayer adsorption process dominated by physical sorption and co-existing with chemical adsorption.The adsorption capacity of pollutants on aged MPs was higher than that on original MPs,and the adsorption performance was in the order of aged PLA>aged PE>original PLA>original PE.In addition,adsorption experiments have shown that the mechanism of adsorption of heavy metals and organic dyes by MPs includes electrostatic interactions,surface complexation,and hydrogen bonding.（3）The adsorption of cationic pollutants on MPs was also affected by the surrounding environment.Through electrostatic interaction,alkaline solutions will increase adsorption.As p H increases,negatively charged MPs will enhance the adsorption of cationic pollutants.The increase in ionic strength leads to a decrease in the adsorption capacity of MPs for cationic pollutants,indicating that MPs interact not only with heavy metals but also with other ions.The adsorption capacity decreases gradually as the fulvic acid concentration rises.（4）The desorption of MPs in simulated intestinal fluid was greater than that in distilled water.In addition,aged treatment reduced the desorption of contaminants from MPs,indicating that aged MPs may be more harmful to organisms than virgin microplastics.Therefore,the potential hazard of MPs to organisms is greater than the potential hazard to the aquatic environment,and MPs carrying contaminants may have adverse effects on aquatic organisms after ingestion.Thus,MPs with attached contaminants are more harmful to the aquatic environment.In summary,the aging process of MPs in the environment affects their role as carriers of co-occurring pollutants.These results contribute to understanding the environmental behavior of MPs,providing information on the environmental risk of MPs to contaminants,and assessing the actual role of MPs in the environment.更多还原