| PE-Cd复合污染土壤中Cd释放迁移特征及机制 |
| 摘要点击 1087 全文点击 175 投稿时间：2023-03-06 修订日期：2023-04-19 |
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| 中文关键词 聚乙烯（PE） 微塑料 吸附 镉（Cd） 淋溶迁移 土壤 |
| 英文关键词 polyethylene （PE） microplastics adsorption cadmium（Cd） leaching soil |
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| 中文摘要 |
| 微塑料广泛分布于土壤环境中，不仅改变了土壤的理化性质还可富集重金属等污染物，进而影响它们在环境中的归趋.目前，有关微塑料对土壤中重金属运移影响的作用机制尚不清晰.选取聚乙烯（PE）微塑料和Cd为研究对象，在明确PE对Cd2+吸附作用机制的基础上，通过土柱淋溶实验研究了不同离子强度和类型（Ca2+、Na+）下，PE含量和粒径对土壤中Cd释放迁移行为的影响.结果表明，PE对Cd2+的吸附能力随粒径的增大而降低，以物理吸附为主，受颗粒内扩散过程控制.PE对Cd释放迁移的影响与CaCl2浓度有关，高离子强度下（0.05 mol·L-1和0.1 mol·L-1），PE促进了Cd2+的迁移，Cd2+的出流浓度分别由6.48 mg·L-1和16.79 mg·L-1升高到7.12 mg·L-1和23.45 mg·L-1；低离子强度下（0.01 mol·L-1）抑制了Cd的迁移，Cd2+的出流浓度由0.66 mg·L-1降低至0.57 mg·L-1； 且PE添加量越大，促进或抑制作用越显著.同时，Cd的释放迁移也受PE粒径和含量的影响，当添加量较小（1%、4%）时，大粒径对Cd2+迁移的促进效果更加显著；而当添加量较大（7%和20%）时，小粒径更易促进Cd2+的迁移.当淋溶液为NaCl时，土壤的渗透性显著降低，PE对Cd的迁移无显著影响，但改变了土壤团聚体的稳定性.总之，微塑料改变了土壤中Cd的释放迁移行为，作用结果不仅与微塑料的粒径和含量有关，还受土壤溶液化学性质的影响. |
| 英文摘要 |
| Microplastics （MPs） are a type of emerging contaminants that pose a potential threat to global terrestrial ecosystems. The accumulation of MPs in soil inevitably affects soil physical and chemical properties， both directly and indirectly. Additionally， owing to their small size and surface features， MPs have excellent sorption capacity for both organic and inorganic materials， thus affecting their fate in the environment. However， the influence of MPs on heavy metal sorption and transport in soil is still not fully understood. In this study， polyethylene （PE） and Cd were selected as research objects， and on the basis of clarifying the adsorption mechanism of Cd on PE MPs， the effects of PE concentration and particle size on Cd release and transport behavior in soil under different ionic strengths and types （Ca2+ and Na+） were studied using column leaching experiments. The results of the batch experiments showed that the adsorption capacity of PE MPs for Cd2+ decreased with the increase in particle size. Scanning electron microscopy （SEM）， Fourier transform infrared spectroscopy （FTIR）， and Zeta potential were used to analyze the properties of PE MPs and adsorption behavior of Cd2+ onto MPs. The adsorption was mainly a physical process and was controlled by intra-particle diffusion. The adsorption kinetics could be described well by the quasi-second-order kinetics and Webber-Morris model. The adsorption isotherm conformed to the Langmuir model， indicating monolayer adsorption. The results of leaching experiments showed that the effect of PE MPs on Cd release and transport in soil was related to the CaCl2 concentration. At high ionic strength （0.05 mol·L-1 and 0.1 mol·L-1）， PE promoted the transport of Cd. The effluent concentration of Cd2+ increased from 6.48 mg·L-1 and 16.79 mg·L-1 to 7.12 mg·L-1 and 23.45 mg·L-1， whereas at low ionic strength （0.01 mol·L-1）， Cd transport was inhibited by PE MPs， and the effluent concentration of Cd2+ decreased from 0.66 mg·L-1 to 0.57 mg·L-1. The larger the amount of PE added， the more significant the promoting or inhibiting effect. Additionally， the release and transport of Cd in soil were also affected by the MPs particle size and concentration. When the addition amount was small （1%， 4%）， the large-sized MPs were more conducive to the transport of Cd in soil. When the addition amount was large （7%， 20%）， MPs with small particle sizes promoted Cd2+ transport more significantly. When the leaching solution used was NaCl， soil permeability decreased significantly. PE MPs had no significant effect on Cd release and transport but changed the stability of soil aggregates. In conclusion， PE MPs could change the release and transport behavior of Cd in soil， and the impact results were not only related to the particle size and content of MPs but were also influenced by the chemical properties of the soil solution. |
