Characterization of organic contaminants and assessment of remediation performance in subsurface formations

Characterization of organic contaminants in subsurface formation is performed by methods for detecting the presence of nonaqueous phase liquid in a subsurface formation, and for determining the composition and for determining the volume of nonaqueous phase liquids. Generally the methods comprise introducing one or more partitioning tracers and one or more non-partitioning tracers at one or more injection points located in the subsurface formation and measuring separation between the one or more partitioning tracers and the one or more non-partitioning tracers from one or more sampling points located in the subsurface formation to determine presence, composition and/or volume of nonaqueous phase liquid in the subsurface formation. In addition, the methods can be used to assess the performance of an attempted remediation.