Laboratory study of heterogeneous processes relevant to the marine troposphere

Heterogeneous gas-liquid interactions play a fundamental role in chemical transformations of atmospheric gases and aerosols. This work examines gas-liquid interactions of several gas-phase species found in marine environments. The laboratory experiments were performed using two complementary techniques: the bubble train flowtube and the droplet train flowtube. In both techniques, the uptake rate of gas species is determined by monitoring the number density of the gas as it interacts with a well-characterized liquid surface.; The following three studies were performed using the bubble train apparatus: (1) Uptake of gas phase chlorine by aqueous surfaces was measured as a function of pH (pH = 1–11.5) and temperature (274–300 K). The uptake data yielded the second order rate constant for the aqueous phase reaction Cl₂(aq) + OH− (aq) → HOCl(aq) + Cl − (aq) as a function of temperature. (2) Uptake of isoprene (C₅H₈) and ozone by aqueous surfaces was measured as a function of NaCl concentration in the liquid (0–4 M) and temperature (274–300 K). The uptake data yielded the Henry's law and Setchenow coefficients for isoprene as well as the second order rate constant for the aqueous phase reaction C₅H₈(aq) + O₃(aq) as a function of temperature. (3) Uptake of DMS ((CH₃) ₂S) and ozone by aqueous surfaces was measured as a function of temperature (274–300 K). The uptake data yielded the Henry's law coefficients for DMS as well as the second order rate constant for the aqueous phase reaction DMS(aq) + O₃(aq) → DMSO(aq) + O₂(aq) as a function of temperature.; The following study was performed using the droplet train apparatus: (4) Uptake of 17O labeled gas-phase water by aqueous sulfuric acid surfaces was measured as a function of acid concentration (50 to 82 wt% H₂SO₄) and temperature (252–295 K). The uptake data yielded the mass accommodation coefficient of water vapor on aqueous sulfuric acid droplets.; The atmospheric importance of these experimental results is discussed.