『Abstract
The objective of this study was to investigate the impact of
flow, transport and geochemical parameters in the unsaturated
and saturated zones on the release of SO4
from overburden lignite spoil piles into the adjacent lake. A
vertical one-dimensional model was set up using the reactive transport
simulator SULFIDOX in order to account for the unsaturated zone.
The SULFIDOX model was calibrated for effective diffusion using
measured Of in the gas phase and SO4 concentrations
in the liquid phase from the unsaturated zone of the heap. The
results show high sensitivity to O2 supply
and initially present gypsum, but the inclusion of secondary mineral
precipitation in equilibrium is of minor importance for the results.
To account for the transport of released SO4
from the saturated zone into the surface water, scenarios were
performed by using SULFIDOX results as input concentration for
a two-dimensional vertical model set up with PROCESSING MODFLOW
and MT3D. These scenarios indicate a rising discharge of SO4 into the adjacent lake due to continued pyrite
weathering for 80 a. Results are highly sensitive to dispersivity,
whereas the spatial variability of pyrite distribution did not
show any influence on the results. The consideration of initially
present gypsum shows a major effect on the modelled SO4
release.』
1. Introduction
2. Study area
3. Methods
3.1. Sediments
3.2. Borehole sampling of porewater and gas
4. Analytical results
4.1. Sediments
4.2. Porewater and gas
5. Model setup
5.1. Conceptual model
5.1.1. Unsaturated zone
5.1.2. Saturated zone
5.2. Set up and combining of numerical models
5.2.1. The vertical one-dimensional model (SULFIDOX)
5.2.2. The vertical two-dimensional hydraulic model (PROCESSING
MODFLOW)
5.2.3. The vertical two-dimensional transport model (MT3D)
6. Results and discussion
6.1. Calibration of the SULFIDOX model
6.2. Sensitivity studies using the SULFIDOX model
6.3. Prognostic simulations
6.3.1. Unsaturated zone scenarios
6.3.2. Saturated zone scenarios
6.3.3. Comparing calculated results and field data of the saturated
zone
7. Conclusions
Acknowledgements
References