Dynamic source apportionment of heavy metals in Bohai Bay sediments using a temporally hierarchical PCA-APCS-HBM...

This study investigated heavy metal pollution in the Tianjin coastal area of Bohai Bay. Sediment samples were collected annually from 2018 to 2023, and the contents of seven heavy metals (mercury (Hg), copper (Cu), lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and zinc (Zn)) were determined. A hierarchical Bayesian receptor model (PCA-APCS-HBM) was applied alongside statistical analysis to elucidate the spatiotemporal distribution, interannual trends, and dynamic source contributions. Results showed a spatial pattern of higher metal contents in the central-northern region than in the south. Hg and Zn were significantly enriched near the Yongding-Xinhe River estuary, while Cu was elevated near the Haihe River estuary, indicating potentially localized terrestrial inputs. Temporally, Hg and Cr generally declined, As and Pb peaked in 2021, Cd remained low after 2018, and Cu and Zn showed minor fluctuations. Source apportionment identified industrial/historical agricultural sources as the stable primary contributor to Cr. Their contributions to Cu and As decreased initially, then rebounded. Specific industrial sources contributed variably to Hg and Cd, with Hg reaching 68.1% in 2021, aligning with its content peak. Contributions from historical atmospheric deposition/non-riverine sources increased consistently for all metals. The findings demonstrate that heavy metal pollution results from dynamic multi-source inputs and spatial hydrodynamic processes, requiring integrated spatiotemporal and source-specific management strategies. The developed dynamic source apportionment framework provides a scientific basis for precise pollution control in bay environments.