This open access book synthesizes important advances in the assessment and management of soil and groundwater systems contaminated with petroleum hydrocarbons, especially in the form of light non-aqueous phase liquids (LNAPLs). LNAPL characterization and remediation is challenging due to the multi-phase, multi-component nature of the problem and the various physical, chemical, and biological processes involved in a dynamic and heterogeneous hydrogeological setting. This book focuses on the current state of practice of LNAPL characterization and remediation and seeks to provide information and a framework that would allow some of these complexities to be better addressed by contaminated land practitioners, researchers, and regulators.

1. Introduction Challenges of LNAPL remediation.- 2. Subsurface flow and transport in heterogeneous media.- 3. Evolution of our understanding on LNAPL distribution.- 4. Novel formulations of capillary pressure-fluid saturation relationships.- 5. LNAPL mobility, transmissivity, and recoverability.- 6. The new paradigm of natural source zone depletion.- 7.Advances in field characterisation methods.- 8. High-resolution site characterisation.- 9. Geophysical investigations.- 10.LNAPL dissolution and the mass flux approach.- 11.Vapour intrusion.- 12. Advances in risk assessment.- 13. Remediation strategies.- 14. Remediation endpoints.- 15. Case study on natural source zone depletion.- 16.Case study on high-resolution site characterisation.- 17.Case study on risk management.- 18. Persistent questions and future directions.