Managing polycyclic aromatic hydrocarbons and their derivatives in soil: Fate, transformation and treatment for emerging pollutant governance

Polycyclic aromatic hydrocarbons (PAH) remain priority soil contaminants, but remediation design and post-treatment verification are still dominated by the 16 parent PAH and total-concentration endpoints. This review argues that such endpoints are insufficient for aged field soils, where weathering, sequestration, mass-transfer limitation, derivative formation, exposure availability, and soil-function recovery jointly control residual risk. Evidence for PAH derivatives provides a quantitative basis for this concern: 188 environmental PAH-derivative compounds have been compiled, including 44 nitrated, 36 oxygenated, 56 alkylated, and 52 halogenated PAH derivatives, whereas only 11 occurrence studies reported soil concentrations. Available soil records identify dozens of derivatives and show concentration ranges from sub-ng/g levels to site-specific hot-spot values near 1000 ng/g, so upper-bound values should not be treated as typical soil concentrations. We synthesize fate, accessibility, transformation, and treatment evidence within a PAC-management framework. Physical and extraction-based methods are useful for source reduction and transfer control but require secondary-stream management. Thermal technologies offer strong destruction potential, yet soil-function costs depend on temperature window, heating severity, and matrix response. Chemical oxidation, electrochemical, photocatalytic, and plasma-assisted systems can enhance transformation or delivery but require verification of incomplete oxidation and derivative formation. Biological and nature-based strategies better support soil recovery but are slower and accessibility-limited. We propose derivative-aware monitoring that integrates parent PAH, selected derivative panels, bioaccessibility/exposure-fraction assays, porewater/leachate and off-gas/condensate endpoints, ecotoxicity assays, suspect and non-target screening, and field validation. Future remediation should move from parent-PAH removal toward risk-based PAC management linking contaminant fate, accessible exposure, transformation products, toxicity response, soil function, and site-specific governance.