Coastal Transformation and PAH Contamination in Bohai Bay (1995-2025): A Remote Sensing and Environmental Assessment

Yida Liu

doi:10.54097/3yffjb75

Authors

Yida Liu

DOI:

https://doi.org/10.54097/3yffjb75

Keywords:

Environmental science, Remote sensing, Marine pollution, Unsupervised classification, PAH, Bohai Bay coastline.

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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