Size-dependent promotion effect of carbon materials on pak choi growth and suppression on di-(2-ethylhexyl) phthalate accumulation

• Size-dependent effect of carbon materials on pak choi growth and DEHP accumulation • The micron-sized carbon material at 500 mg kg⁻¹ significantly enhanced pak choi growth • The micron-sized carbon material markedly suppressed DEHP uptake by pak choi • Micro-nano carbon materials did not induce significant shifts in soil microbial community The safe and efficient utilization of phthalate-contaminated farmland soils has emerged as a critical scientific and technological challenge, particularly in regions with high plastic consumption. Carbon-based materials, owing to their favorable structural and physicochemical properties, have shown promising potential for soil remediation. However, the influence of particle size and application rate of carbon materials on the migration and transformation behavior of phthalates in the soil-plant system remains poorly understood. This study investigated the regulatory effects of micro-nano carbon materials with varying particle sizes and application rates on the growth of pak choi ( Brassica rapa var. chinensis ) and its uptake and accumulation of di-(2-ethylhexyl) phthalate (DEHP). The dissipation of DEHP in soil and associated changes in microbial community structure was also explored. The results demonstrate that the impact of micro/nano carbon materials on both soil DEHP dissipation and plant uptake were highly dependent on particle size and concentration. Application of micron-sized carbon material at 500 mg kg⁻¹ significantly suppressed DEHP dissipation in soil, while simultaneously enhancing plant height, root fresh weight, and shoot fresh weight of pak choi by 0.68, 5.6, and 4.9-fold, respectively. Furthermore, the micron-sized carbon material markedly suppressed DEHP uptake by the shoots of pak choi, reducing DEHP content in shoots by 65%, thereby effectively mitigating the associated dietary health risks. Notably, the addition of micro-nano carbon materials did not induce significant shifts in soil microbial community structure. This study provides a feasible technical strategy and theoretical foundation for the safe utilization of phthalate-contaminated farmland using micro-nano carbon materials.