Unveiling polycyclic aromatic hydrocarbon pollution dynamics in river-lake sediments: Insights for energy transition.

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants primarily emitted by heavy industry, while their relationship with light industry has remained largely overlooked. This study quantified 16 priority PAHs in sediments from an urbanized river and its tributaries using gas chromatography coupled with triple quadrupole mass spectrometry, assessing the impact of local light industries. The total sedimentary PAH concentrations ranged from 244 to 24,616 ng/g dw (mean: 2097 ± 2673 ng/g dw), with high molecular weight PAHs predominating. PAH concentrations closely mirrored the operational footprint of the textile and shipping industries, including significantly higher PAH concentrations in the midstream compared to the upstream and downstream areas with fewer industrial activities. Additionally, PAH concentrations were significantly higher in the rainy season in the semi-closed lakes than in the dry season and normal season, likely due to increased industrial production and shipping activity, combined with the periodical closure of sluice gates that restricts the outflow of PAHs from connected lakes to the main watercourse. Multiple statistical analyses revealed that coal and petroleum combustions, primarily from these local industries, contributed 88% to the sedimentary PAH load, while vehicle exhausts and oil leakages accounted for the remaining 12%. According to sediment quality guidelines, PAHs exhibited pervasive ecological risks, even near drinking water sources. This study highlights the substantial influence of industrial activities on PAH distribution in urbanized rivers and provides a robust theoretical foundation for energy transition and drinking water protection strategies.