Theme 3: Acid and alkaline soils
Soil degradations by acid and alkaline groundwater seepages are
different manifestations of groundwater discharges in relation to
rising watertables. They occur in both coastal and inland environments.
Acid sulphate soils develop by the mobilisation of sulphur compounds
during repeated oxidation and reduction in rising groundwaters
in sulphur-rich regolith. During this process metals from underlying
rocks may be mobilised, concentrated and again released in acid
seeps. These same toxic scalds are also a window on the geochemistry
of underlying basement rocks, which is of interest to mineral explorers.
Likewise, degraded alkaline scalds are a common part of inland salt-affected
soils. Alkaline discharges are often associated with silcrete, calcrete
and gypsum, but the sources, stores and transport mechanisms of
the main ingredients - sodium and calcium are not known.
Again there are important links between MINEX and NRM applications.