Uptake of Organic Acids on Ice Surfaces: Evidence for Surface Modification and Hydrate Formation

作者：Symington Angela; Cox R Anthony^*; Fernandez Miguel A

来源：Zeitschrift für Physikalische Chemie, 2010, 224(7-8): 1219-1245.

DOI：10.1524/zpch.2010.6149

• Organic Acids
• Ice
• Surfaces Modification
• Hydrate Formation

The uptake of gaseous HC(O)OH CH(3)C(O)OH and CF(3)C(O)OH on ice films at temperatures corresponding to the upper troposphere (UT) has been investigated using a coated wall flow tube with mass spectrometric measurement of gas concentration Uptake was largely reversible and followed Langmuir type kinetic behavior i e surface coverage increased with trace gas concentration approaching a maximum surface coverage at N(max) similar to 2 to 3 X 10(14) molecules cm(-3) corresponding to similar to 25% monolayer (ML) The partition constants K(LinC) were obtained from the experimental data by analysis using the simple Langmuir model and also using a simple one dimensional numerical model to simulate individual uptake profiles and retrieve partition constants for specific conditions of temperature and concentration over the temperature range 208-238 K The analysis showed that Langmuir constants decreased at high surface coverages possibly due to adsorbate adsorbate interaction or modification of the ice surface At low cover age the following expressions described the temperature dependence of the partition coefficients (K(LinC)) for HC(O)OH (K(LinC) = (1 5 +/-(1 0) (3 5)) X 10(-8) exp((5143 +/- 268)/T) cm) for CH(3) C(O)OH (K(LinC) = (0 55 +/-(0 5) (5 4)) X 10(-8) exp((5703 +/- 536)/T) cm) and CF(3)C(O)OH (K(LinC) = (512 +/-(1903)(404)) X 10(-8)exp((309 +/- 331)/T) cm) For CF(3)C(O)OH there was an irreversible component of uptake which was attributed to hydrate formation on the surface

• 出版日期2010