This two-part thesis describes the analysis of environmental pollutants at depth without bringing sample to the surface. In the first part a new high temperature transfer line, membrane inlet probe HTTL-MIP) coupled to a photoionization detector PID) and gas chromatograph/mass spectrometer GC/MS) was used to rapidly profile and speciate polycyclic aromatic hydrocarbons PAH) in the subsurface. PID signals were in agreement with GC/MS results. Correlation coefficients of 0.92 and 0.99 were obtained for discrete and composite samples collected from the same exact location. Continuous probe advancement with PID detection found coal tar, a dense nonaqueous liquid, in soil channels and saturated media. When samples were collected conventionally, split, solvent extracted and analyzed in the field and confirmation lab, GC/MS measurement precision and accuracy were indistinguishableï¼› despite the fact the field lab produced data five times faster than the lab using standard EPA methods. No false positive/negatives were found. Based on these findings, increased confidence in site conceptual models should be obtained, since PID response indicated total PAH presence/absence in “real-time,” while GC/MS provided information as to which PAH was present and at what concentration. Incorporation of this tool into a dynamic workplan will provide more data at less cost enabling environmental scientists, engineers, and regulators to better understand coal tar migration and its impact on human health and the environment. The second part of this thesis is based on an improved 3-stage Peltier freeze trap, which efficiently pre-concentrates volatile coal tar and petroleum hydrocarbons, and an integrated system for detecting pollutants on-line, in real time by photoionization detection and quantitation by gas chromatography/mass spectrometry GC/MS) as the probe is advanced into the subsurface. Findings indicate measurement precision and accuracy for volatiles meet EPA criteria for hazardous waste site investigations. When a Teflon membrane inlet is used to detect contaminants in groundwater, its 140 &ordmï¼›C temperature limit restricts analyte collection in soil to C2-phenanthrenes. Two case studies demonstrate the probe is well-suited to tracking petroleum and coal tar plumes from source to groundwater. Key words: in situ sampling probe, subsurface, dense non aqueous phase liquids, hazardous waste site characterization, photoionization detector, GC/MS