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The Influence of Root Exudates on the Aggregation Effect of Nanoplastic Particles
Summary
Researchers investigated how plant root exudates influence the aggregation behavior of charged polystyrene nanoplastics (PSNPs) using hydroponic experiments with Astragalus membranaceus, finding that root exudates — particularly sugars — significantly increased PSNP particle size by promoting aggregation, with microbial activity playing a secondary facilitating role.
微/纳米塑料作为全球性环境污染物，广泛存在于各类环境介质中。现有研究已证实其对植物的生长发育存在不利影响，然而植物根系对微/纳米塑料颗粒环境行为的作用却知之甚少。本研究选用携带不同电荷的聚苯乙烯纳米塑料(PSNPs)和蒙古黄芪(Astragalus membranaceus var. mongholicus (Bunge) P.K. Hsiao)为对象，通过植物水培实验与人工模拟根系分泌物，探究根系分泌物对纳米塑料颗粒团聚行为的影响。结果表明，与1/2霍格兰营养液相比，水培蒙古黄芪根系的存在显著增大了培养液中浓度为50和100 mg/L的不同电荷PSNPs的平均水合粒径，且对携带正电荷的PSNPs的影响明显大于未带电及携带负电荷的PSNPs。此外，PSNPs平均水合粒径随培养植物数量的增加而增大。人工模拟根系分泌物中，糖类对PSNPs团聚的促进作用明显强于有机酸，且在无菌条件下该促进作用有所减弱。研究结果显示，植物根系可通过增加分泌物的产生促进PSNPs团聚，以减轻PSNPs的毒害效应，其中根系分泌物中的糖类物质起主要作用，微生物活动也有重要的促进作用。As a global environmental pollutant, micro-nanoplastics are widely distributed in various environmental media. Existing studies have determined that micro-nanoplastics in the environment have an adverse impact on the growth and development of plants. However, little is known about the role of plant roots in the environmental behavior of micro-nanoplastic particles. In this study, polystyrene nanoparticles (PSNPs) with different charges and Astragalus membranaceus var. mongholicus (Bunge) P.K. Hsiao were used as research objects. Through plant hydroponic experiments and artificial simulation of root exudates, the influence of root exudates on the aggregation behavior of nanoplastics particles was investigated. The results showed that, compared with the 1/2 Hoagland nutrient solution, the presence of the roots of hydroponically cultured Astragalus membranaceus significantly increased the average hydrated particle size of PSNPs with different charges at concentrations of 50 and 100 mg/L in the culture solution. Among them, the influence on the positively charged PSNPs was significantly greater than that on the uncharged and negatively charged PSNPs. In addition, as the number of cultured plants increased, the average hydrated particle size of PSNPs also increased. The promotion effect of carbohydrates in the artificially simulated root exudates on the aggregation of PSNPs was significantly higher than that of organic acids, and this promotion effect was partially weakened under aseptic conditions. Our research results indicate that plant roots can promote the aggregation of PSNPs by increasing the production of exudates to reduce the toxic effects of PSNPs. Carbohydrate substances in the root exudates play a major role in this process, and microbial activities also have an important promoting effect.