HR: 1340h
AN: H33A-1364    [Abstracts]
TI: Lattice Boltzmann Simulation of Isotope Kinetics in Crystal Growth
AU: * Lu, G
EM: gplu@lbl.gov
AF: Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA 94720 United States
AU: DePaolo, D J
EM: depaolo@eps.berkeley.edu
AF: Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA 94720 United States
AU: DePaolo, D J
EM: depaolo@eps.berkeley.edu
AF: University of California at Berkeley, Department of Earth and Planetary Science, Berkeley, CA 94720 United States
AU: Kang, Q
EM: qkang@lanl.gov
AF: Los Alamos National Laboratory, Earth and Environmental Division, Los Alamos, NM NM 87545 United States
AU: Zhang, D
EM: donzhang@ou.edu
AF: University of Oklahoma, Mewbourne School of Petroleum and Geological Engineering, Norman, OK 73019 United States
AB: There is useful information that comes from isotopic variations resulting from micro-scale processes in the formation of methane hydrate, ice and mineral crystals. Most previous work on isotopic effects resulting from phase changes has used continuum models. This study is aimed at the development of computational tools using the lattice Boltzmann (LB) method to simulate isotopic fractionation during evaporation, condensation and crystal growth. The model relates isotopic fractionation to the chemical saturation state of the growth medium, fluid flow, diffusion and reaction associated with the phase transformations. The effect of reaction relative to that of diffusion is described with a Damkohler number, Da = kr h/D, where kr is the local reaction-rate constant, h is the length dimension of the model domain, and D is the diffusivity. The parameter values are chosen to represent realistic values in natural environments. At low Damkohler numbers, compact "crystals" are formed whereas at high Da, dendritic crystals form. The fractal dimensions of the grown crystals are computed. In situations where molecular isotopomers have different diffusion coefficients, the resultant isotopic ratios of the crystals differ strongly from the equilibrium values when Da values are high and less when Da values are low. The isotopic fractionation can be directly related to crystal morphology, saturation state, and fluid flow. LB simulation provides a novel alternative method to evaluate isotopic kinetics in natural systems, and may be particularly useful for better understanding isotopic effects associated with microphysical processes such as vapor depositional growth of ice crystals in clouds and chemical reactions on atmospheric aerosols.
DE: 0430 Computational methods and data processing
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0736 Snow (1827, 1863)
DE: 1847 Modeling
DE: 3311 Clouds and aerosols
SC: Hydrology [H]
MN: Fall Meeting 2005