Uptake Pathways, Translocation, and Accumulation of Phthalate Esters in Tea Seedlings Under Hydroponic Conditions

Phthalate esters (PAEs) are ubiquitously emerging pollutants in the environment and have a notably high detection rate in tea; they can leach out during consumption and pose potential risks to human health. However, the process of PAEs entering and accumulating in tea plants is undocumented. This study investigated the uptake of PAEs in tea plant seedlings, focusing on both root and foliar pathways under hydroponic conditions. In controlled indoor deposition experiments, PAEs on fresh tea leaves underwent rapid degradation within five days, with the degradation rates ranging from 66.98% to 81.69%; outdoor rates exhibited even higher degradation rates. This degradation process followed first-order kinetics. The results revealed that tea plants were capable of absorbing and translocating PAEs via roots and leaves, culminating in their accumulation in various tea plant tissues. The Root Concentration Factor (RCF) was highest for di(2-ethylhexyl) phthalate (DEHP). Conversely, the shoot concentration factor, Leaf Concentration Factor, and Translocation Factors for the leaves, stems, and roots for the PAEs were inversely related to the RCF. The moderated mediation analysis suggested that root concentration was strongly influenced by translocation-mediated pathways. However, leaf concentration was largely not mediated by the translocation pathways. These findings indicate that both root uptake and foliar deposition can contribute to PAE accumulation in tea plants, providing a basis for source apportionment and for designing targeted control strategies to reduce PAE contamination in tea production systems.