Environmental Engineering Reference
In-Depth Information
chemical integrity.
Soils at the bottom of bodies of water thus need special sampling considerations. They
will often need to be sampled, and represent a unique sampling environment. In addition
to being anaerobic, soil and sediment at the bottom of bodies of water are under pressure.
A field sample taken under these oxygen and pressure conditions must be kept oxygen-
free and under pressure until analyzed. Such samples will frequently be easily dispersed
and this must be avoided as much as possible. The void spaces between soil particles are
completely filled with water, which is called interstitial water. In many cases the
interstitial water and the solid particles will need to be analyzed separately.
2.1.2.1. Solutes in Water
Sometimes people are surprised that a chemical analysis of water can result in finding the
presence of gasoline components, including ethers. The everyday observation is that
these compounds are not soluble in water. There are two answers to this puzzle. First, as
already noted, water is capable of dissolving small amounts of almost any material [11].
Second, analytical methods and instrumentation are extremely sensitive. Detection of
parts per million was once considered good. Today, however, detection of parts per
billion or trillion are routinely and easily made. In some cases it is even possible to look
at single molecules or atoms. The detection of a component in water is thus important,
but it only tells part of the story.
The occurrence of surfactants (soaps) in water will also dramatically increase the
apparent solubility of insoluble compounds. Soaps can come from man-made sources;
however, there are a large number of plants that produce soaplike compounds. Both
sources can lead to solubilization of insoluble compounds and thus increased levels of
these compounds in water.
Suspended, colloidal-sized particles are present in water and carry sorbed material.
This material can show up in analysis and be reported in such a way as to indicate that it
was in solution. In this way components may appear to be present in water in
concentrations above their solubility limit.
2.1.3. The Lithosphere
Geologists classify rocks as being sedimentary, igneous, or metamorphic, depending on
how they were formed. Sedimentary rock is the result of rock and rock components being
eroded, usually into a body of water. The material sediments and comes under enough
pressure to allow the particles to be cemented together. Common sedimentary rocks are
shale, sandstone, and limestone. Most often rock is considered hard; however, many
sedimentary rocks are quite soft. Some are soft enough to allow them to be broken by
hand. Another completely different type of sedimentary rock is coal. This is rock derived
from organic matter and is composed of carbon, and thus is very different from other
types of rock.
Igneous rock results from the cooling of magma (melted rock material) or lava. This
cooling can occur when magma reaches the Earth's surface as lava or when it flows into
cracks in nearby rocks and cools. Common igneous rocks are granite, pumice, and basalt.
 
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