Compound-specific radiocarbon reveals sources and land–sea transport of polycyclic aromatic hydrocarbons in an urban estuary

As typical chemical indicators of the Anthropocene, polycyclic aromatic hydrocarbons (PAHs) and their environmental behavior in urban estuaries can reveal the influence of anthropogenic activities on coastal zones worldwide. In contrast to conventional approaches based on concentration datasets, we provide a compound-specific radiocarbon (¹⁴C) perspective to quantitatively evaluate the sources and land‒sea transport of PAHs in an estuarine‒coastal surficial sedimentary system impacted by anthropogenic activities and coastal currents. Compound-specific ¹⁴C of PAHs and their ¹⁴C end-member mixing models showed that 67−73% of fluoranthene and pyrene and 76−80% of five- and six-ring PAHs in the Jiulong River Estuary (JRE, China) originated from fossil fuels (e.g., coal, oil spill, and petroleum-related emissions). In the adjacent Western Taiwan Strait (WTS), the contributions of fossil fuel to these PAH groups were higher at 74−79% and 84−87%, respectively. Furthermore, as a significant biomarker for source allocation of terrigenous organic matter, perylene, a typical five-ring PAH, and its land‒sea transport from the basin through the JRE and finally to the WTS was quantitatively evaluated based on the ¹⁴C transport models. In the JRE, fluvial erosions and anthropogenic emissions affected the ¹⁴C signature of perylene (Δ¹⁴C_perylene, -535 ± 5‰) with contributions of > 38% and < 62%, respectively. From the JRE to the WTS, the decreased Δ¹⁴C_perylene (-735 ± 4‰) could be attributed to the long‒range transport of “ocean current-driven” perylene (-919 ± 53‰) with a contribution of 53 ± 8%. This compound-specific ¹⁴C approach and PAH transport model help provide a valuable reference for accurately quantifying land‒sea transport and burial of organic pollutants in estuarine‒coastal sedimentary systems.