Climate change may amplify aquatic PAH risks through sediments
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The figure shows PAH transport and projected concentrations in the Yangtze, Huanghe, and St. Lawrence watersheds through 2050. Sediments act as a sink for most PAHs in the Yangtze and Huanghe watersheds but as a net source in the St. Lawrence watershed. Under climate-change scenarios, surface-water PAH concentrations are projected to increase or rebound in the two Chinese watersheds, whereas changes in the St. Lawrence watershed remain comparatively small because of higher PAH degradation rates.
view moreCredit: Carbonsphere, Tsinghua University Press
Semivolatile organic compounds (SVOCs), typified by polycyclic aromatic hydrocarbons (PAHs), are notorious pollutants that significantly affect aquatic ecosystems and public health.Sediments serve as major sinks for anthropogenic PAHs. However, their role in modulating the risks that PAHs pose to aquatic ecosystems under climate change scenarios remains underexplored.
A research team from Nanjing Forestry University, Fudan University, Nanyang Technological University and China Agricultural University set out to determine whether climate change could alter the role of sediments in PAH pollution. Combining long-term observations with a multimedia environmental model, the researchers tracked how 16 priority PAHs move among air, surface water and sediment, focusing on the Yangtze, Huanghe and St. Lawrence watersheds.
The team published their research article in Carbonsphere on July 28, 2026.
“Sediments are often treated as the final destination for hydrophobic pollutants such as PAHs, but our results show that their role is more dynamic,” said Ke Yin, corresponding author of the study and professor in the Department of Environmental Engineering at Nanjing Forestry University.” As climate conditions change, pollutants stored in sediments can continue to influence surface-water exposure. This means that reducing new emissions may not be enough to address long-term PAH risks.”
PAHs are highly hydrophobic and persistent, allowing them to accumulate in aquatic sediments and making sediments important long-term reservoirs for these pollutants. However, sediments are not a permanent endpoint for PAHs. When environmental conditions change, stored PAHs may be released back into the water.
The three watersheds did not behave in the same way. Modeling indicated that sediments acted as a sink for 13 of the 16 PAHs in the Yangtze and Huanghe watersheds, while sediment in the St. Lawrence system acted as a net source to the water. “The same sediment compartment can therefore play very different roles depending on regional environmental conditions,” Yin said.
The climate scenarios revealed a further divergence among regions. Under the high-emissions SSP585 scenario, total modeled ecological risk in the Yangtze watershed was projected to increase by 31%–56% between 2040 and 2050. Risk also increased in the Huanghe watershed, while remaining comparatively low in the St. Lawrence watershed, where faster degradation limits PAH accumulation.
The model suggests that climate change does more than change PAH emissions. Rising temperatures can alter volatilization and the partitioning of PAHs between sediment and water, changing how previously stored pollutants re-enter the aquatic system. By 2050, high-molecular-weight PAHs will dominate the sediment–water exchange pathway, whereas low-molecular-weight PAHs will be largely depleted in sediments.
The findings suggest that controlling new PAH emissions alone may not be enough to reduce long-term contamination of surface waters. Because sediments can store historical pollution and later release PAHs back into the water, the researchers argue that sediment management should be considered alongside emission controls and climate-change adaptation.
The study was conducted by Tingting Sun, Mingliang Fang, Jingyu Zhu, Lusha Zeng, Fanrong Zhao, Changzhi Shi, Shuhan Ren, Ke Yin, Qianhong She and Xunchang Fei, with affiliations including Nanjing Forestry University, Fudan University, China Agricultural University and Nanyang Technological University.
This work was supported by the National Key Research and Development Program of China (Grant No. 2024YFA0918900), the Singapore Ministry of Education and Nanjing Forestry University.
DOI Link:
https://doi.org/10.26599/CS.2026.9510007
Journal
Carbonsphere
Article Title
Climate change increases aqueous ecological risks of semivolatile organic compounds: Meta-analysis and mechanistic modeling in three major watersheds
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