Geoscience Reference
In-Depth Information
Fig. 17.10 Saturation state of the groundwater downstream from the forest for Al(OH)
3
(a),
gibbsite, and jurbanite. Saturation index (SI) = log (IAP/K) = 0 indicates equilibrium between
the groundwater and the specified mineral, SI [ 0 indicates supersaturation, and SI \ 0 indicates
subsaturation (Franken et al.
2009
). Reprinted from Franken et al. (
2009
). Copyright (2009) with
permission from Elsevier
in the aquifer sediment derived from high atmospheric sulfur concentrations and
acid rain.
In northern Europe, high rates of acidic deposition between 1950 and 1980
declined drastically as a result of ecological awareness. However, the rate of
SO
4
2-
decline in surface waters is much slower than that of SO
4
2-
in atmospheric
deposition (Alewell et al.
2001
). During years of high sulfur deposition, significant
amounts of sulfur accumulated in soil remained as a source of groundwater
acidification. Despite the fact that the relationship between acid input into aquifers
and SO
4
2-
concentrations in groundwater has changed over time, there is con-
tinuous transport by leaching of sulfur from soils into groundwater. Thus,
groundwater acidification from anthropogenic sources remains an irreversible
process at least on a human lifetime scale.
17.3 Groundwater Contamination by Inorganic Trace
Elements
Disposal of inorganic trace contaminants onto the land surface, with subsequent
downward transport as dissolved solutes and/or adsorbed on colloids, may lead to
irreversible changes in aquifer chemistry. We illustrate such irreversible changes
in groundwater chemistry by considering the behavior of radionuclides, heavy
metals, and metalloids.
