Spatial ecological risk assessment for contaminated soil in oiled fields.

Area of Science:

• Environmental Science
• Soil Science
• Petroleum Engineering

Background:

• Total petroleum hydrocarbon (TPH) contamination in oil fields poses a significant global environmental challenge.
• Dense oil well distribution in low-permeability reservoirs exacerbates regional pollution superposition.
• Existing assessment methods lack spatial ecological considerations for TPH-polluted oil fields.

Purpose of the Study:

• To propose and validate a feasible method for spatial ecological assessment of soil TPH pollution in oil fields.
• To analyze the spatial distribution and influencing factors of TPH contamination in the Shengli oil field.
• To evaluate the ecological risks associated with TPH pollution using multiple receptors and risk sources.

Main Methods:

• Examined TPH-contaminated soil based on oil well properties (spatial structure, density, exploitation history).
• Calculated soil TPH concentrations using Monte Carlo simulation.
• Assessed ecological risks using multiple receptors (wheat, earthworms, bacteria) and the soil quality index.

Main Results:

• Average TPH concentration exceeded 2100 mg·kg⁻¹.
• TPH concentration differences were primarily correlated with the exploitation period.
• Soil TPH content exhibited a significant spatial cluster pattern (Anselin Local Moran's Index, p < 0.01).
• Over 98% of the area posed a low ecological risk to wheat and earthworms.
• High risk to bacteria was observed in only 0.9% of the area, aligning with soil quality index assessments.

Conclusions:

• The developed spatial ecological assessment method effectively characterizes TPH pollution in oil fields.
• Exploitation history is a key factor influencing TPH concentration and spatial distribution.
• While overall ecological risk is low for some receptors, specific bioindicators like bacteria highlight localized high-risk areas requiring targeted remediation.