Heterogeneous accommodation and reaction kinetics in the laboratory and the atmosphere
- Boston College, Chestnut Hill, MA (United States)
Heterogeneous interactions of gases with cloud droplets and aerosol particles are now recognized to play a critical role in many atmospheric processes. We describe results of experiments that measure the uptake of trace gases into liquid water and sulfuric acid solutions on time scales ranging from 10{sup -3} to 10 seconds, with rates corresponding to uptake (or {open_quote}sticking{close_quote}) coefficients between 10{sup -7} and 1. Time dependent uptake rates resolve the relative contributions of mass accommodation probability, gas and liquid diffusion, gas solubility, and aqueous reactivity to overall gas/liquid mass transport rates. Uptake of NH{sub 3} exemplifies the range of observed behavior. In basic solution, (pH>10) uptake is limited by physical solubility (Henry`s law constant, H{approximately}100 M/atm), with enhanced uptake observed at t<10{sup -2} sec indicative of a surface complex. At lower pH, uptake increases as NH{sub 3} reacts with H+ in solution. At low pH<2, uptake reflects the mass accommodation coefficient ({approximately}0.08 at 283K) which exhibits a negative temperature dependence consistent with a cluster nucleation model. In concentrated sulfuric acid solution the NH{sub 3} uptake coefficient increases to near unity, independent of temperature, indicative of enhanced surface reactivity.
- OSTI ID:
- 370016
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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