A TUNABLE LASER BASED MONITOR FOR HOCI AND HCI IN THE MARINE TROPOSPHERE

THE POSSIBILITY THAT ATOMIC CHLORINE CONCENTRATIONS IN THE MARINE SURFACE LAYER ARE LARGE ENOUGH TO COMPETE WITH OH AS THE MAJOR TROPOSPHERIC OXIDIZER HAS RECEIVED CONSIDERABLE SPECULATION. CHLORINE ATOMS PARTICIPATE IN THE OXIDATION OF HYDROCARBONS AND DIMETHYL SULFIDE AND CAN ALSO DIRECTLY INFLUENCE TROPOSPHERIC OZONE LOSS THROUGH CATALYTIC CYCLES WITH C1O AND HO2 RADICALS. THE NET EFFECT ON THE OZONE BUDGET MAY BE HIGHLY DEPENDENT ON THE PARTITIONING OF THE INORGANIC CHLORINE POOL BETWEEN HC1, HOC1, C12, AND C1ONO2. IN ORDER TO ASSESS THE POTENTIAL IMPORTANCE OF CHLORINE CHEMISTRY, DIRECT MEASUREMENTS OF THESE SPECIES ARE NECESSARY. RESEARCHERS ARE ASSESSING THE FEASIBILITY OF DETECTING HOC1 AT THE 10 TO 20 PPT LEVEL USING TUNABLE DIODE LASER INFRARED ABSORPTION. THIS REQUIRES: (1) MEASUREMENT OF PRESSURE BROADENING COEFFICIENTS FOR SELECTED ABSORPTION LINES; (2) IDENTIFICATION OF SUITABLE SPECTRAL REGIONS; (3) INVESTIGATION OF PHOTOLYTIC MODULATION OF HOC1 TO IMPLEMENT BACKGROUND SUBTRACTION; AND (4) DESIGN OF NOVEL MULTIPLE PASS ABSORPTION CELL WITH A PATH LENGTH OF AT LEAST 600 METERS.