A DIODE LASER FLUXMETER FOR MEASUREMENT OF ATMOSPHERIC DRY DEPOSITION

THIS STUDY IS TO DEVELOP INSTRUMENTATION TO MEASURE DRY DEPOSITION RATES OF ATMOSPHERIC TRACE GASES IM- PORTANT IN STUDIES OF ACIDIC DEPOSITION. THE METHOD IS BASED ON THE WELL-ESTABLISHED EDDY CORRELATION TECHNIQUE AND WILL USE A TUNABLE DIODE LASER SOURCE COMBINED WITH AN OPEN-PATH MULTIPASS ABSORPTION CELL FOR TRACE SPECIES DETECTION AT PARTS-PER-BILLION LEVELS. THIS INSTRUMENT WILL HAVE THE FAST TIME RESPONSE (<0.1S) AND SHORT MEASUREMENT PATH (<1M) REQUIRED FOR THE EDDY CORRELATION METHOD. DESIGNS FOR OPEN-PATH ABSORPTION CELLS WILL BE EVALUATED, AND VARIOUS DATA ACQUISITION APPROACHES WILL BE TESTED FOR MAXIMUM SENSITIVITY TO VALIDATE THE MEASUREMENT CONCEPT. TESTS WILL BE CONDUCTED IN COMBINATION WITH A LABORATORY TUNABLE DIODE LASER SYSTEM AND WILL INCLUDE MEASUREMENTS OF SELECTED TRACE GASES IN ATMOSPHERIC PRESSURE AIR. OPTIMUM DETECTION WVELENGTHS FOR SEVERAL GASES WILL BE DETERMINED, INCLUDING NITRIC OXIDE, NITROGEN DIOXIDE, NITRIC ACID, SULFUR DIOXIDE, OZONE, HYDROGEN PEROXIDE, AND NITROGEN PENTOXIDE. THE RESULTS OF PHASE I ARE EXPECTED TO RESOLVE CRITICAL DESIGN ISSUES AND PERMIT THE DEVELOPMENT OF FIELD INSTRUMENTATION IN SUC- CEEDING PHASES.