H. Huang et Bx. Hu, Nonlocal reactive transport in heterogeneous dual-porosity media with rate-limited sorption and interregional mass diffusion, WATER RES R, 37(3), 2001, pp. 639-647
Huang and Hu [2000] developed a nonlocal, first-order, Eulerian theory for
the mean concentration of a conservative tracer in a dual-porosity medium.
Here the results of Huang and Hu are extended to reactive chemical transpor
t under linear nonequilibrium sorption in both mobile and immobile zones. S
imilar to Huang and HM [2000], a two-zone, mobile and immobile, model [van
Genuchten and Wierenga, 1976] is adapted to account for the interregional m
ass transfer. Hydraulic conductivity in the mobile zone, sorption coefficie
nts in both zones, and interregional mass diffusion rate are all assumed to
be spatial random variables to account for the inherent spatial variabilit
y of physical and chemical properties of a natural medium. The analytical s
olution for mean concentration in mobile water is given explicitly in Fouri
er-Laplace space and numerically converted to real space via a fast Fourier
transform method. The results are simplified to conservative transport in
a dual-porosity medium [Huang and Hu, 2000] and reactive transport in a one
-zone model [Hu et al., 1995] under appropriate conditions. The solution pr
ovides a tool to investigate the validity of an "effective sorption" method
, where various chemical sorption and physical mass transfer processes are
treated as a sorption process with effective sorption parameters. This stud
y shows that chemical sorption and interregional mass diffusion may be lump
ed together as an effective sorption process under specific conditions. Gen
erally speaking, however, such simplification will lead to a significant er
ror in prediction of the plume evolution, especially at late travel time. I
t is also shown that randomness of the interregional mass transfer process
will significantly enhance the plume spreading and lead to a more negativel
y skewed plume.