Laboratory investigations of heterogeneous chemistry important to ozone depletion in the stratosphere. Ph.D. Thesis

Thesis/Dissertation · Fri Dec 31 04:00:00 EST 1993

OSTI ID:147178

Zhang, R

Results of laboratory investigations of heterogeneous chemistry important to ozone depletion in the stratosphere are presented. Thermodynamic properties (such as melting points, enthalpies of fusion, etc.) for acids which are present in the stratosphere (HCl, HNO3, and H2SO4) are studied using laboratory-assembled apparatus of electrical conductivity and differential thermal analysis and using a commercial differential scanning calorimeter (DSC). Vapor pressures and infrared spectra of liquid and supercooled solutions, and of liquid-solid and solid-solid coexistence mixtures for the HCl/H2O and H2SO4/H2O binary systems are investigated. Equilibrium constants and standard enthalpies of formation for the pure crystalline hydrates of those acids as well as their corresponding liquid compositions are determined from the vapor pressure and calorimetric data. A theoretical approach, which allows determination of vapor pressures for two adjacent hydrates in thermodynamic equilibrium and for the coexistence systems involving a hydrate and ice in a binary system, is presented in terms of chemical equilibrium principles and compared with the experimental data for thermodynamic consistence. Vapor pressures of HNO3 and HCl over H2SO4/HNO3/H2O and H2SO4/HCl/H2O solutions as well as over H2SO4/HNO3/HCl/H2O solutions are also measured in order to predict incorporation of stratospheric acids into the background sulfate aerosols. From the data, the Henry`s law solubility constants for those systems are determined and the equilibrium compositions of aqueous stratospheric aerosols are predicted as a function of ambient temperature and mixing ratios of H2O and HNO3. The results indicate that at the low temperatures characteristic of the stratosphere at high latitudes in the winter and spring, the HNO3 content reaches levels of the order of 10 percent wt in the background sulfate aerosols.

• Research Organization: Massachusetts Inst. of Tech., Cambridge, MA (United States)
• OSTI ID: 147178
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AEROSOLS
ATMOSPHERIC CHEMISTRY
HETEROGENEOUS EFFECTS
HYDROCHLORIC ACID
INFRARED SPECTRA
NITRIC ACID
SOLUBILITY
STRATOSPHERE
SULFURIC ACID
THERMODYNAMIC PROPERTIES
VAPOR PRESSURE