An Illustrated Handbook of LNAPL Transport and Fate in the Subsurface

This illustrated handbook presents best-practice guidance for the assessment and remediation of light non-aqueous phase liquids (LNAPLs) in the subsurface. LNAPLs notably include fuels and oils, for example petrol (gasoline), diesel and heating oils, and are amongst the most commonly encountered organic contaminants in the subsurface environment due to their ubiquitous use, accidental release and, perhaps, poor (historical) disposal. Central to this handbook and the management of risks posed is the development of conceptual models of LNAPL behavior in common hydrogeological systems.

LNAPLs typically comprise a complex mixture of predominantly hydrocarbon organic chemicals with a wide range of physical-chemical and toxicological properties that may influence their environmental fate and risks posed (Section 2). Their subsurface transport is complex, being a multi-phase (LNAPL-water-air) flow problem, but nevertheless is often characterized by an accumulation of buoyant hydrophobic LNAPL in the vicinity of the water table interface that has potential to migrate laterally (perhaps seeping to surface water receptors) or redistribute vertically due to natural or human-induced water table fluctuations (Section 3). Further risks to groundwater resources and wells may often arise from the wider migration of a dissolved-phase plume that may develop from the subsurface LNAPL source, although these may be mitigated by natural attenuation processes, notably biodegradation (Section 4.1). Also, risks to receptors at ground surface, for example building inhabitants, may arise from volatile LNAPL constituents that form subsurface vapor plumes (Section 4.2). The above sections underpin the development of conceptual models of LNAPL transport and fate across a comprehensive range of common hydrogeological systems (Section 5). This is considered the handbook hub from which local conceptual site models may be developed that fundamentally support both the characterization and investigation of sites (Section 6) and the management and remediation of sites designed to address unacceptable risks posed (Section 7).

The handbook provides an illustrated blend of technical detail and real world conceptualization of the LNAPL problem and appropriate methods to investigate and manage it. The handbook also facilitates access to a wealth of detailed research, guidance and case study literature within the various topics covered. It will be useful to the practitioner and research communities, and also provide a valuable educational resource to others having a less direct interest or specialized knowledge.