Abstract
Polycyclic aromatic hydrocarbons pose inconsistent yet increasing threats to freshwater reservoirs worldwide, with implications for ecosystem health and water security. Although local-scale contamination has been widely documented, a comprehensive global synthesis of polycyclic aromatic hydrocarbon occurrence and drivers in reservoirs remains lacking. Here we developed a framework of data compilation, arrangement and statistics to integrate existing data to determine the geographical distribution and potential sources of polycyclic aromatic hydrocarbon pollution in reservoirs globally. Statistical analyses revealed spatial heterogeneity in dominant components and pollution levels across continents. Almost 38% of water samples exceeded an ecologically relevant threshold (0.20 μg l−1), and 42% of sediment samples surpassed the threshold effect concentration, indicating widespread ecological risks. Cluster analysis and source apportionment of the reservoir-level data identified three distinct polycyclic aromatic hydrocarbon patterns, each shaped by region-specific land-use practices, combustion sources and climatic factors. These findings emphasize and inform the need for region-specific monitoring and management strategies, such as expanding monitoring in subtropical and temperate regions, with a focus on polycyclic aromatic hydrocarbon accumulation in aquatic organisms.
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Data availability
The datasets that support the findings of this study are available via figshare at https://doi.org/10.6084/m9.figshare.30626969 (ref. 51). Source data are provided with this paper.
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Acknowledgements
This work was financially supported by the Young Scientists Program of the National Natural Science Foundation of China (grant number 42307066 to Z.-F.G.), the National Key Research and Development Program of China (grant number 2025YFE0111301 to Y.-Y.X. and Z.-F.G.) administered by the Ministry of Science and Technology, the Open Competition Mechanism to Select the Best Candidates Program (grant number IUE-JBGS-202203 to Y.-Y.X.) from the Institute of Urban Environment, Chinese Academy of Sciences (IUE, CAS) and the Ningbo S&T project (2021-DST-004 to Y.-Y.X.) at the Ningbo Science and Technology Bureau.
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Z.-F.G. and Y.-Y.X. conceptualized the research. Z.-F.G., Y.-Y.X. and D.L. collected and analysed the data. Z.-F.G., W.J.B., Y.-Y.X., E.B., O.A.A.-M., D.L. and X.-R.Y. contributed to the interpretation of the results and paper writing. Z.-F.G. and Y.-Y.X. acquired funding. All authors contributed to the final manuscript and approved its submission.
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Nature Geoscience thanks Yonghong Bi, Belén González-Gaya and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Alison Hunt, in collaboration with the Nature Geoscience team.
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Extended data
Extended Data Fig. 1 Relationship between ∑16PAH concentration and distance from the dam.
Correlations were evaluated using two-sided Pearson’s tests (df = n-2). For each fitted relationship, coefficient of determination (R²) and p-values are reported in the corresponding panels. Linear regressions were fitted only when |Pearson’s r | ≥ 0.3 and R² ≥ 0.15. Shaded areas denoted 95% confidence intervals. All statistical analyses were performed using two-sided tests without adjustment for multiple comparisons.
Extended Data Fig. 2 ∑PAH concentrations at different sampling depths within an individual reservoir.
Different colors represent different sampling sites of sediments: Vossoroca (VS, Cluster α), Osaka Castle (OC, Cluster β), Echo (EC, Cluster γ), Fosdic (FS, Cluster γ), Como (CO, Cluster γ).
Extended Data Fig. 3 Heterogeneity of PAH composition in different environmental media.
Analysis of similarities (ANOSIM) was used to test the null hypothesis that PAH compositions do not differ signidicantly among environmental media. Correlations were evaluated using a two-sided, permutation-based test (999 permutations). The r statistic (effect size) and p-values are shown in the corresponding panels. y-axis indicates the degree of dissimilarity between and within groups. Boxplots display the distribution of rank dissimilarities: centre line = median, box = 25th–75th percentiles, whiskers = min/max within 1.5 times interquartile range (IQR), points beyond whiskers = outliers. Statistical significance is denoted as “*” for p < 0.05 and “**” for p < 0.01. For Loskop Reservoir, sediment (n = 18, N = 9) and water (n = 16, N = 9) samples were collected from nine sites during flood and storage seasons; for Blachownia, sediment (n = 5, N = 4) and water (n = 20, N = 4), and for Cedara, sediment (n = 4, N = 4) and water (n = 4, N = 4) samples were collected across seasons. Each n denotes an independent field sample (biological replicate). PAH concentrations were meansured in triplicate (technical replicates), and mean values were used for analyses.
Extended Data Fig. 4 Interannual and seasonal variation in PAH concentrations from reservoir water and sediment.
The blue represents water and the green is sediment. Seasonal comparisons were evaluated using two-sided Mann–Whitney U tests, and interannual variations using two-sided Kruskal–Wallis tests with Dunn’s post-hoc tests (Bonferroni adjustment). Statistical significance is denoted as “*” for p < 0.05. Boxplots show the distribution of PAH concentrations: centre line = median, box = 25th–75th percentiles, whiskers = min/max within 1.5 times interquartile range (IQR), points beyond whiskers = outliers. Sampling sites included the Three Gorges (water N = 59; sediment N = 13), Shuikou (N = 10), and Loskop (water N = 24; sediment N = 14) reservoirs across multiple years and hydrological seasons (see Supplementary Data 1). Each n denotes an independent field sample (biological replicate).
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Source data for Figs. 1–4, Extended Data Figs. 1–4 and Extended Data Table 1.
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Guo, ZF., Boeing, W.J., Xu, YY. et al. Regionally distinct threats from polycyclic aromatic hydrocarbons in global reservoirs. Nat. Geosci. 19, 68–74 (2026). https://doi.org/10.1038/s41561-025-01872-4
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DOI: https://doi.org/10.1038/s41561-025-01872-4

