Coastal Transformation and PAH Contamination in Bohai Bay (1995-2025): A Remote Sensing and Environmental Assessment
Bibliographic record
Abstract
Understanding the relationship between coastline variation and polycyclic aromatic hydrocarbon (PAH) pollution is critical for assessing long-term ecological risks in rapidly industrializing coastal zones. While previous studies have assessed how the Bohai Bay coastline expansion influences the water dynamics and the land-use type, few studies have integrated the spatial-temporal shoreline evolution with pollutant dynamics in the Bohai Bay region. This study addresses that gap by extracting the coastlines from 1995 to 2025 based on Landsat imagery. An unsupervised classification approach named the ISODATA algorithm, guided by the Normalized Difference Water Index (NDWI) calculation results, was employed to differentiate land from water bodies. Then, the automated spatial tools were integrated with manual editing procedures to ensure accurate shoreline extraction. The historical length of shoreline was then combined with the PAH concentration data from existing literature to explore the relationship between coastal change and pollution accumulation. Primary results reveal significant seaward expansion of the coastline, particularly between 2005 and 2015, driven by land reclamation and industrial development. The study also showed an overall increase of traditional polycyclic aromatic hydrocarbons (t-PAHs) concentrations in the marine environment from 1995 to 2020, with high-molecular-weight (HMW) compounds dominating intertidal zones due to their low solubility and sediment affinity. However, a reduction in PAH levels in recent years is expected due to regulatory reforms, improved fuel standards, and reduced coal dependency. The study concludes that coastal geomorphological change is one of the major factors that influences the pollutant distribution and ecological exposure. Its contribution lies in linking geospatial analysis with environmental contamination analysis; it offers a reproducible workflow and highlights the need for continuous in situ monitoring for environmental assessment. These observations support sustainable coastal management and inform policy decisions in marine pollution control.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".