Hh. Gerke et al., Modelling the impact of physical and chemical heterogeneity on solute leaching in pyritic overburden mine spoils, ECOL ENG, 17(2-3), 2001, pp. 91-101
Spatial variability of physical and chemical properties may affect acidific
ation and acid mine drainage in sulfide-bearing overburden mine spoils. Thi
s study compares heterogeneous with vertically layered and horizontally ave
raged spatial distributions of chemical components in a generic 2D-vertical
spoil cross-section with heterogeneous distributions of water and air cont
ents and of water flux densities. The initial spatial distributions of the
fraction of sulfur and the pre-oxidized zones follow autocorrelated random
functions. The initial background chemistry distribution is correlated to t
he degree of pre-oxidation using five classes of differing initial chemical
systems. Processes considered include variably saturated water flow, oxyge
n diffusion, shrinking-core kinetics of pyrite oxidation, multicomponent re
active solute transport, and geochemical equilibrium reactions between aque
ous and mineral components. Spatial distributions were generated using the
SGSIM-GSLIB geostatistical simulation algorithm and estimated parameters. R
esults: show differences in vertical concentration profiles of chemical com
ponents and in integrated breakthrough curves at 30 m depth between the het
erogeneous and the layered case for both-high and low-sulfur content scenar
ios. Differences are relatively large in the beginning and with respect to
the distribution of solid phase components. A heterogeneous sulfide mineral
distribution results in vertical spreading of the oxidation front while pr
ecipitation and dissolution of the secondary minerals affects the acid mine
drainage, by locally retarding and releasing the solutes. (C) 2001 Elsevie
r Science B.V. All rights reserved.