离子类型、强度和铁氧化物影响下微塑料的迁移行为及模型计算  

Transport and Model Calculation of Microplastics Under the Influence of Ionic Type,Strength,and Iron Oxide

作　　者：张然 于可飞 黄磊 陈雅丽 马杰 翁莉萍 李永涛[3] ZHANG Ran;YU Ke-fei;HUANG Lei;CHEN Ya-li;MA Jie;WENG Li-ping;LI Yong-tao(Agro-Environmental Protection Institute,Ministry of Agriculture and Rural Affairs,Tianjin 300191,China;College of Resources and Environment,Huazhong Agricultural University,Wuhan 430070,China;College of Natural Resources and Environment,South China Agricultural University,Guangzhou 510642,China)

机构地区：[1]农业农村部环境保护科研监测所,天津300191 [2]华中农业大学资源与环境学院,武汉430070 [3]华南农业大学资源环境学院,广州510642

出　　处：《环境科学》2023年第9期5102-5113,共12页Environmental Science

基　　金：中央级科研院所基本科研业务费专项(2022-jbkyywf-cyl)。

摘　　要：土壤中的微塑料(MPs)作为一种新型污染物而被广泛关注,其迁移行为受到自身理化性质、土壤溶液化学组成和土壤矿物等因素的影响.目前,铁氧化物存在时,离子类型和离子强度对MPs迁移行为的影响机制尚不明确.通过稳定性实验和迁移实验,重点考察了离子类型、离子强度和铁氧化物对带有不同官能团聚苯乙烯微塑料(PSMPs)迁移行为的影响,并用胶体迁移模型、 CD-MUSIC模型及DLVO理论探讨其迁移机制.结果表明,PSMPs在NaH_(2)PO_(4)背景下的稳定性最强,标准化浓度(c/c0)达到0.99,而在CaCl2背景下的稳定性相对弱,c/c0降低至0.94.不同离子种类对PSMPs的迁移行为产生不同影响,对于阳离子Na^(+)和Ca^(2+),二价Ca离子有架桥作用和较强的电荷中和作用,更能阻滞PSMPs在石英砂中的迁移,出水溶液中PSMPs回收率低至(43.83±1.71)%且第二动力学位点上的一级保留系数k_(2a)为1.54 min^(-1),铁氧化物会进一步加剧阻滞作用,回收率降低为(6.04±0.40)%且k_(2a)升高为5.33min^(-1);对于阴离子Cl-和PO_(4)^(3-),PSMPs在纯石英砂柱中的迁移主要受其自身表面电负性的控制,Cl-离子下PSMPs电负性更低,回收率升高[(92.95±0.63)%]且k_(2a)降低(0.19min^(-1)),而当铁氧化物存在时,PSMPs的迁移则受控于载铁石英砂表面的Zeta电位.CD-MUSIC模型计算结果显示PO_(4)^(3-)容易吸附在铁氧化物表面形成内圈络合物,降低载铁石英砂表面的电负性,因此PSMPs在PO_(4)^(3-)背景下的回收率升高[(76.22±1.39)%]且k_(2a)降低(0.66min^(-1));同时,该内圈络合物的形态受PO_(4)^(3-)浓度的控制且不同形态的内圈络合物具有不同的表面负电荷数,因此高PO_(4)^(3-)浓度下载铁石英砂表面电负性反而高,不利于PSMPs迁移.此外,PSMPs的迁移均随着离子强度的增加而降低.最后,DLVO理论计算出不同条件下PSMPs和介质间的一级势垒变化趋势与PSMPs的迁移能力一致,即较高的一级势垒表明Microplastics(MPs)in soil have attracted extensive attention as an emerging pollutant,and the transport of MPs is affected by their own physical and chemical properties,the chemical composition of soil solutions,and soil minerals.However,in the presence of oxides,the underlying mechanism for the transport of MPs in different ionic types and ionic strengths is still not fully understood.In this study,the effects of ionic type,ionic strength,and iron oxide on the transport of polystyrene microplastics(PSMPs)with different functional groups were investigated through stability experiments and transport experiments.The colloid transport model,CD⁃MUSIC model,and DLVO theory were used to explore the transport mechanism.The results showed that normalized concentrations(c/c0)of PSMPs were 0.99 in the NaH_(2) PO_(4) background and 0.94 in the CaCl2 background,respectively,which indicated that the strongest stability of PSMPs was observed in the former and the weakest in the latter.Different ionic types had different effects on the transport of PSMPs.For the cations Na^(+)and Ca^(2+),Ca^(2+)strongly inhibited PSMPs transport in pure quartz sand because of the bridging effect and strong charge neutralization effect;the recovery rate of the PSMPs in the effluent was(43.83±1.71)%,and a first⁃order retention coefficient on the second kinetic Site⁃2(k_(2a))was 1.54 min^(-1).The presence of iron oxide enhanced the inhibition,the recovery rate of the PSMPs in the effluent decreased to(6.04±0.40)%,and k_(2a) increased to 5.33 min^(-1).For the anions Cl-and PO_(3)-4,the transport of PSMPs in pure quartz sand was dominated by surface electronegativity of PSMPs,and PSMPs exhibited lower electronegativity under Cl-background and thus showed higher recovery[(92.95±0.63)%]and lower k_(2a)(0.19 min^(-1)).However,in the presence of iron oxides,the Zeta potential of the quartz sand surface was the controlling factor for PSMPs transport.According to results of the CD⁃MUSIC model,PO_(3)-4 could be easily adsorbed on the iron oxide

关 键 词：微塑料(MPs) 迁移 离子类型 离子强度 铁氧化物 

分 类 号：X131[环境科学与工程—环境科学]