Hydrocarbon seep monitoring using in situ deep sea mass spectrometry

Hydrocarbon seep monitoring is an area applicable for new advances in mass spectrometry. Recent developments are allowing unprecedented levels of trace contaminant measurement in the deep ocean. With funding from the U.S. National Science Foundation (NSF), our engineering design team constructed a new mass spectrometer-based in situ analysis system for work in the deep ocean environment over prolonged deployment periods. Our design goals were a depth capability of up to 4,000 m water depth (400 bars hydrostatic pressure) and autonomous operation for periods of up to six months to a year, depending upon type of external battery system used or other deployment circumstances, e.g., availability of a power cable or fuel cell power source. We chose a membrane introduction mass spectrometry (MIMS) sampling approach, which allows for dissolved gases and volatile organics introduction into the MS vacuum system. The MIMS approach and the hydrophobic, silicon-coated membrane chosen both draw upon our previous experience with this technology in the deep ocean. The membrane has been tested to 400 bars in a series of long-term hydrostatic pressure tests, which extends the 200-bar working depth rating of this membrane by a factor of 2. Long-term deployment capability of the moderately powered, approximately 100 W system, was accomplished by power management of the embedded computer system and custom electronics, with Windows-based and custom software now fully developed and bench tested.