Geoscience Reference
In-Depth Information
Chapter 18
Contaminant Impacts
on the Soil-Subsurface Solid Phase
In this chapter, we consider irreversible changes to the soil-subsurface solid phase
matrix and properties that, under specific conditions, may be caused by chemical
contamination. We present examples from the literature that show irreversible
changes in the soil-subsurface system caused by contaminants originating from
agrochemical practices, irrigation with saline water, and disposal of municipal and
industrial products. We suggest that chemical contamination of the natural soil-
subsurface solid phase may lead to the formation of a ''new'' soil-subsurface
porous medium with matrix and properties different than those of the natural one.
18.1 Impact of Contaminants Originating from Agriculture
A portion of chemicals periodically applied onto the land surface as fertilizers, plant
protection chemicals, and reclamation amendments may be retained irreversibly on
the soil-subsurface solid phase, leading to changes in natural soil properties. For
example, continuing use of ammonia-based fertilizers can induce soil acidity, while
long-term application of phosphorus may lead to an increase in bicarbonate-
extractable phosphorus relative to untreated plots. Trace elements (micronutrients)
may be affected by the soil pH and, consequently, by the long-term addition of
nitrogen- and phosphorus-containing compounds (Schwab et al.
1990
, and refer-
ences therein). Soil-subsurface alkaline and acid properties may be changed by
chemical amendments such as gypsum and lime, affecting also the fate of other
agrochemicals, which together may lead directly or indirectly to changes in soil-
subsurface physical properties. We consider several specific examples below.
