ATMOSPHERIC TRACE GAS FLUX METER USING TUNABLE DIODE LASERS

THE PURPOSE OF THE PROPOSED STUDY IS THE DEVELOPMENT OF INSTRUMENTATION TO MEASURE FLUXES OF ATMOSPHERIC TRACE GASES TO OR FROM THE EARTH'S SURFACE. THE METHOD WE PROPOSEIS BASED ON THE WELL ESTABLISHED EDDY CORRELATION TECHNIQUE AND WOULD USE A TUNABLE DIODE LASER LIGHT SOURCE COMBINED WITH A MULTIPLE PASS ABSORPTION CELL TO DETECT TRACE SPECIES AT SUB-PART-PER-BILLION LEVELS. THE PROPOSED INSTRUMENT WOULD BE DESIGNED SPECIFICALLY TO BE INTERFACED WITH A SONIC ANEMOMETER TO PROVIDE FAST TIME RESPONSE (<0.1S) AND MINIMAL FLOWFIELD INTERFERENCE AS REQUIRED FOR THE EDDY CORRELATION METHOD. IN THE PHASE I STUDY, DESIGNS FOR A REDUCED PRESSURE TRACE GAS SAMPLING SYSTEM WILL BE EVALUATED AND TESTED, AND A MULTIPLE PASS ABSORPTION CELL WHICH MAXIMIZES THE PATH LENGTH AND MINIMIZES INTERFERENCE FRINGES WILL BE DESIGNED AND EVALUATED. THE RESULTS OF THE PHASE I EFFORT ARE EXPECTED TO RESOLVE CRITICAL DESIGN ISSUES AND PERMIT THE DEVELOPMENT OF FIELD INSTRUMENTATION IN SUCCEEDING PHASES. THE FINAL INSTRUMENT WILL BE APPLICABLE TO FLUX MEASUREMENTS OF TRACE GASES INCLUDING SULFUR DIOXIDE, NITRIC OXIDE, NITROGEN DIOXIDE, NITRIC ACID,OZONE, AND HYDROGEN PEROXIDE.