By tracking seasonal changes in water and sediments, researchers show that these tributaries intensify pollution risks to aquatic ecosystems, particularly during the wet season, while human health risks remain below current safety thresholds.
PAEs are synthetic chemicals extensively used as plasticizers in construction materials, medical devices, packaging, and personal care products. Because they are not chemically bound to plastics, they readily escape into the environment during manufacturing, use, and disposal. Many PAEs are recognized as endocrine disruptors and potential carcinogens, raising concerns about long-term ecological and health effects. China is the world’s largest consumer of PAEs, and previous studies have documented their presence in major rivers. However, the role of urban tributaries and sediments—especially under changing seasonal conditions—has been poorly understood, limiting effective pollution control strategies.
A study (DOI: 10.48130/ebp-0025-0015) published in Environmental and Biogeochemical Processes on 26 December 2025 by Zulin Zhang’s team, Wuhan University of Technology, combines chemical analysis with sediment–water partitioning models and ecological and human health risk assessments, providing an integrated picture of contamination sources, transport processes, and potential impacts.
Using seasonal field sampling across the Wuhan section of the Yangtze River mainstream and eight urban tributaries, the researchers quantified 16 phthalate acid esters (∑16PAEs) in paired surface-water and sediment samples, then compared spatiotemporal patterns (dry vs. wet season; mainstream vs. tributaries) and evaluated sediment–water exchange using measured sediment–water partition coefficients (Kp) against theoretical distribution coefficients (Kd), followed by ecological risk calculations (single-compound RQs for algae, crustaceans, and fish plus mixture risk RQmix) and human health risk screening (non-carcinogenic hazard indices and carcinogenic risk for DEHP). This method revealed that ∑16PAEs in surface water ranged from 40.57 to 2,464 ng/L (mean 1,183 ng/L), with all congeners except BBP detected and five compounds—DMP, DEP, DIBP, DBP, and DEHP—present in every sample and contributing >95% of total PAEs; overall levels exceeded those reported previously for the mainstream largely because the tributaries were more contaminated (tributaries: 141.9–2,464 ng/L; mean 905.1 ng/L), while the mainstream here (40.57–1,909 ng/L; mean 651.2 ng/L) was comparable to earlier data. Sediments showed ∑16PAEs of 141.7–4,314 ng/g (mean 708.4 ng/g), with 14 congeners consistently detected (DnHP and DNP absent), the same five dominant PAEs at 100% frequency, and relatively stable composition across seasons (DEHP and DBP together ~84–85%), indicating sediments as a persistent reservoir. Seasonal comparisons showed higher concentrations in both water (dry mean 415.1 ng/L vs. wet mean 1,183 ng/L) and sediments (dry mean 488.5 ng/g vs. wet mean 708.4 ng/g; p<0.05), consistent with runoff and wet deposition effects. Spatially, tributaries were generally more polluted than the mainstream—especially in the dry season—with hotspots in Fu and Sheshui Rivers (water means up to ~2,000 ng/L; sediment in Fu River up to 4,315 ng/g). Partitioning analysis found Kp ranked DEHP>DBP>DIBP>DMP>DEP in both seasons (e.g., DEHP 35.54 L/g dry; 4.21 L/g wet), and Kp often exceeded Kd for several congeners, signaling potential secondary release from sediments, more evident in tributaries during the wet season. Risk assessments aligned with these patterns: ecological risks were higher in the wet season, DEHP was the most hazardous, RQmix in water shifted to consistently high in wet season (mean 4.27), sediments were uniformly high-risk across sites (RQmix always >1), while human health indices remained below safety thresholds, with sensitivity typically children>women>men.
These findings shift attention away from the river mainstream and toward tributaries and sediments as priority targets for pollution management. Controlling discharges from urban tributaries, managing runoff during the wet season, and addressing contaminated sediments could substantially reduce overall PAE loads and ecological risks in large river systems.
##
References
DOI
Original Source URL
https://doi.org/10.48130/ebp-0025-0015
Funding Information
This work was supported by the Joint Fund of Zhejiang Provincial Natural Science Foundation of China under Grant No. LLSSZ25B050001, 'Pioneer' and 'Leading Goose' R&D Program of Zhejiang (Grant No. 2024SSYS0103), and the Scottish Government's Rural and Environment Science and Analytical Services Division (RESAS).
About Environmental and Biogeochemical Processes
Environmental and Biogeochemical Processes is a multidisciplinary platform for communicating advances in fundamental and applied research on the interactions and processes involving the cycling of elements and compounds between the biological, geological, and chemical components of the environment.
Experimental study
Not applicable
Spatiotemporal distribution, migration behaviors, and ecological risks of phthalate esters in tributaries and mainstream of the Yangtze River, Wuhan section
26-Dec-2025
The authors declare that they have no competing interests