College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China.
Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, Hunan Province, PR China.
Sci Total Environ. 2024 Dec 1;954:176322. doi: 10.1016/j.scitotenv.2024.176322. Epub 2024 Sep 17.
Microplastics (MPs) and heavy metals often coexist in soil, however their interactions and effects on the soil-plant system remain largely unclear. In this study, ramie (Boehmeria nivea L.) was exposed to soil contaminated with lead (Pb) and polystyrene (PS) of different sizes, dosages, and surface-charged functional groups. This design aimed to simulate the effects of MPs on phytoremediation. The experimental results revealed that PS exacerbated the damaging effects of Pb on ramie. Compared to the effect of Pb alone, PS-COOH had a greater influence on root vigor, leading to a 15.6 % reduction in the active absorption ratio. Laser scanning confocal microscope showed PS entered the roots. Adsorption/desorption experiments demonstrated that PS had a weaker adsorption capacity for Pb than soil but a greater desorption rate than soil when simulating rhizosphere secretion. Moreover, PS reduced soil pH and increased the reducible state of Pb by 6-12 %. After 100 days of phytoremediation, Pb content in the soil with PS-5 μm was 150 μg g less than that in the soil without PS. These results demonstrated that PS improved Pb bioavailability and enhanced the efficiency of Pb uptake by ramie. The redundancy analysis demonstrated that PS mitigated the toxicity of Pb to rhizosphere microorganisms, potentially via its effects on metal chemical fractions, dehydrogenase activity (S-DHA), cation exchange capacity (CEC), and soil organic matter (SOM). This study indicates that the presence of PS could potentially enhance the phytoremediation efficiency of ramie in Pb-contaminated land by influencing soil microenvironmental properties. This study provides insights into the complex interactions of MPs with soil-plant-microbial systems during metal remediation, thereby enhancing our understanding of their environmental impacts.
微塑料（MPs）和重金属通常共存于土壤中，但它们之间的相互作用及其对土壤-植物系统的影响在很大程度上仍不清楚。在本研究中，苎麻（Boehmeria nivea L.）暴露于受不同尺寸、剂量和表面带电官能团的聚苯乙烯（PS）和铅（Pb）污染的土壤中。该设计旨在模拟 MPs 对植物修复的影响。实验结果表明，PS 加剧了 Pb 对苎麻的破坏作用。与单独 Pb 的影响相比，PS-COOH 对根活力的影响更大，导致主动吸收比降低了 15.6%。激光扫描共聚焦显微镜显示 PS 进入了根系。吸附/解吸实验表明，PS 对 Pb 的吸附能力比土壤弱，但在模拟根际分泌时，解吸率比土壤高。此外，PS 降低了土壤 pH 值，并将 Pb 的可还原态增加了 6-12%。经过 100 天的植物修复后，添加 PS-5μm 的土壤中 Pb 的含量比没有 PS 的土壤少 150μg g。这些结果表明 PS 提高了 Pb 的生物有效性，并增强了苎麻对 Pb 的吸收效率。冗余分析表明，PS 通过影响金属化学形态、脱氢酶活性（S-DHA）、阳离子交换量（CEC）和土壤有机质（SOM），减轻了 Pb 对根际微生物的毒性。本研究表明，PS 的存在可能通过影响土壤微环境特性，增强苎麻在 Pb 污染土地上的植物修复效率。本研究深入了解了 MPs 与土壤-植物-微生物系统在金属修复过程中的复杂相互作用，从而增强了我们对其环境影响的理解。
