Spatiotemporal Heterogeneity of Soil Physicochemical Properties and Hydrocarbon Distribution in Coastal Oilfields of the Yellow River Delta

The ecological stability of the Yellow River Delta (YRD) is increasingly challenged by intensive petroleum exploitation. This study presents a comprehensive investigation into the spatial distribution and vertical stratification of soil pollutants across 12 representative wellhead sites (YT1-YT12) in a coastal oilfield. By integrating field monitoring data with multi-dimensional statistical analysis, we characterized the variations in soil pH, electrical conductivity (EC), total petroleum hydrocarbons (TPH), and ionic compositions (K+, Na+, Ca2+, Mg2+, Cl−, So42−) across horizontal distances (5–50 m) and vertical depths (0–40 cm). Our findings reveal that soil pH and EC exhibit a decaying gradient with increasing distance from the wellhead, while TPH concentrations demonstrate significant accumulation in specific ecological zones, reaching a peak of 124.0 mg/kg at site YT12. Vertical analysis indicates that TPH and major ions primarily sequester in the 20–40 cm layer, influenced by the root systems of native halophytes like Phragmites australis. This research provides a quantitative framework for assessing the environmental footprint of oilfield operations in sensitive wetland ecosystems and offers data-driven insights for targeted ecological remediation.