Integrated assessment of soil quality and contaminant risks in salinized farmland adjacent to an oil-exploitation zone: insights from the Yellow River Delta

Intensified industrial activities significantly threaten farmland soil integrity, particularly in salinized regions. However, comprehensive evaluations of soil fertility and contamination by polycyclic aromatic hydrocarbons (PAHs) remain limited. In this study, we assessed soil quality in China's Yellow River Delta (YRD) by quantifying 13 indicators of soil physicochemical and biological properties, along with 11 PAHs. Our findings reveal that the minimum data set approach provides a robust and comprehensive representation of overall soil fertility. Salinity emerged as the primary limiting factor, with strong correlations between salinity and key ions, highlighting its adverse effects on soil structure and function. Additionally, significant PAH contamination was detected, particularly from benzo[a]anthracene (BaA), fluoranthene (Flu), and chrysene (Chr), as indicated by the Nemerov pollution index. A pronounced negative correlation between the soil quality index (SQI) and the soil environmental index (SEI) underscores the substantial role of PAH pollution in soil degradation. Notably, the SQI integrates both SEI and soil fertility, providing a holistic assessment of soil health. These findings highlight the utility of SQI as a diagnostic tool for evaluating soil degradation and emphasize the need for targeted remediation strategies to address salinity and PAH contamination, thereby promoting soil restoration and agricultural sustainability.