IN-SITU MEASUREMENTS OF AIR SAMPLES FROM GROUNDWATER WELLS WITH A FIELD DEPLOYABLE MASS SPECTROMETER

Groundwater management requires periodic monitoring of aquifer wells to ensure water quality is maintained. Water samples are typically pulled for analysis to meet these requirements. Some contaminants also have low vapor pressures, and will volatilize on contact with open air. Additional gaseous compounds in a well shaft may also provide clues as to the dissolution process taking place within the aquifer. In this experiment, a field deployable mass spectrometer fit with 60 m of polytetrafluoroethylene (PTFE) tubing was used to sample the air within the well shaft above the water’s surface. A series of scans were taken from two wells, a distance of 7 meters apart, but drilled to different depths and into different geologic layers. Results from the two wells were distinctly different, and one well showed the potential presence of methane, C₂ and C₃ hydrocarbons, NO and H₂S. Although the results are preliminary, the potential for well airspace analysis with the field deployable mass spectrometer are promising.