Characteristics of the Environment - Field Sampling: Principles and Practices in Environmental Analysis - page 27

Changes in the oxygen content of soil affect both the chemistry and biology therein.
Changes in the anaerobic/aerobic and oxidizing/reducing conditions of a soil sample
affect the oxidation states of the metal cations it contains, the oxidation state of nitrogen
compounds, and whether or not organic matter is decomposed by aerobic or anaerobic
mechanisms. It also affects the primary types of organisms living in the sample. These
organisms, particularly microorganisms, are responsible for many chemical changes in
the environment. For this reason changes in the organisms present in a sample can
dramatically affect the results of an analytical procedure.
The atmosphere can affect the field sampling in many ways and should always be kept
in mind. Samples that are oxidizing must be kept that way. Likewise, soils under
reducing conditions must be kept in a reducing environment [10].
FIGURE 2.2 An example of a karst landscape.
2.1.2. The Hydrosphere
The solution making up the hydrosphere comprises water containing small amounts of
dissolved gases and inorganic and organic ions and molecules. Water, with its familiar
chemical formula H 2 O, is of fundamental importance, both in the environment and in
environmental sampling. Water has unique chemical and physical characteristics and
chemical reactivity related to hydrogen bonding and attraction to both positive and
negative atoms or charges in other molecules. (See Figure 2.3.) It is often called the
universal solvent because even the most insoluble components are to a measurable extent
soluble in water [2, 11].
Layers of water occur in both oceans and lakes. In northern temperate regions lakes