What Is Present - Field Sampling: Principles and Practices in Environmental Analysis - page 222

dioxide. Nitrogen represents approximately 80% of air and oxygen 20%, with carbon
dioxide being 0.003%. Note that argon, which is never mentioned, makes up 1% [1]!
Additionally, water can be as much as 5% of the soil atmosphere.
FIGURE 9.2 Inorganic composition of rock and soil before and after
weathering. Data taken from Ref. 10.
9.2. THE INORGANIC COMPONENTS
When discussing the specific inorganic contents it might be good to start with those
present in elemental form. The gaseous phase contains nitrogen, oxygen, argon, and in
the regolith, radon. Both nitrogen and argon are considered to be inert in the
environment. On the other hand, oxygen is very reactive and necessary for respiration by
most organisms and plant roots. Helium and radon can also be found in the soil
atmosphere and are particularly apparent near geologic fault lines [2, 3]. Even mercury
gas (Hg gas) has been reported in the regolith atmosphere [4]! There is little in the way of
elements in the hydrosphere, soil solution, and water in either the regolith or in rock