The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles

Abstract

Abstract.Using a multidiagnostic approach the rate R ev [molec cm −3 s −1 ] or flux J ev [molec cm −2 s −1 ] of evaporation of H 2 O and its corresponding rate constant for condensation, k cond [s −1 ], on a 1 µm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H 2 O on ice unchanged. The resulting Arrhenius expressions for pure ice are J ev = 1.6 · 10 28±1 · expHCl mole fraction in the range 3.2 · 10 −5 − 6.4 · 10 −3 :, and a HBr mole fraction smaller than 6.4 · 10 −3 : J ev = 7.4 · 10 25±1 · expThe small negative activation energy for H 2 O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is H subl = E ev − E cond = 11.9 ± 2.7 kcal mol −1 , H subl = 11.2 ± 2.8 kcal mol −1 , and H subl = 11.7 ± 2.8 kcal mol −1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol −1 . Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl-and HBr-contaminated ice particles by a factor of 3-6 and 10-20, respectively, for submonolayer coverages of HX once the fraction of the ice not contaminated by HX has evaporated.

Water Accommodation and Desorption Kinetics on Ice

“…In addition, we expect water accommodation to be strongly affected by the formation of a liquid-like surface layer as the temperature approaches the melting point, 38−40 and the validity range for the present kinetic model remains to be determined. A majority of earlier studies suggest that α deviates significantly from unity above 200 K. The prediction from the precursor model agrees favorably with experimental data from Rossi and co-workers 21,22,24,25,31 and Earle et al, 32 while other data sets are either lower 3,8 or higher 36 than the predicted values. There are several possible uncertainties that may have affected the different types of experiments.…”

H<sub>2</sub>O and HCl trace gas kinetics on crystalline and amorphous HCl hydrates in the range 170 to 205 K: the HCl/H<sub>2</sub>O phase diagram revisited

“…In this work we expand on the results of Delval et al (2003) by measuring the kinetics of HCl and H 2 O interaction on HCl-doped ice substrates whose phase-identity is known, namely HCl hexahydrate or an amorphous HCl/H 2 O mixture, in the temperature range 170-205 K. We also discuss the effect of surface disorder on α and we propose a revision of the phase diagram of the binary HCl/H 2 O system based on the 25 results obtained for the HCl hexahydrate substrates.…”

“…Given the nature of the experiments, namely laminar flow tubes and Knudsen reactors, neither is able to identify the 15 nature of the substrate as they have no means of investigating the condensed phase under the relevant conditions of the uptake experiment. Using a stirred flow reactor similar to the one used in this work, Delval et al (2003) provided a γ value ranging from 0.05 to 0.01 in the temperature range 200 to 235 K and are able to identify the nature of the substrate by means of FTIR spectroscopy in transmission. Figures and HCl, both separately and in the presence of each other, in order to resolve the difficulties in the quantitative determination of HCl adsorption onto the ice substrate.…”

Cirrus clouds, humidity, and dehydration in the tropical tropopause layer observed at Paramaribo, Suriname (5.8°N, 55.2°W)

“…The questions remain, why would the cloud not evaporate completely in the subsaturated environment on the timescale of days? Probably, the low temperatures and the presence of trace species like HNO 3 , HCl, HBr, or some organics even in small amounts could effectively slow down the evaporation rate [Delval et al, 2003] and thus allow the detection of this extremely thin layer of particles. The green line in Figure 6i shows the existence temperature of Nitric acid trihydrate (NAT) according to a formula provided by Hanson and Mauersberger [1988] using a mixing ratio of 0.3 ppbV of HNO 3 in the TTL which seem realistic [Jensen and Drdla, 2002].…”