Geoscience Reference
In-Depth Information
period, 6-7 million years ago. Hence, even marine systems can
experience shortages of H
2
O.
Reservoirs
C
O
N
P
10
2
10
6
10
6
- Atmosphere
7.2
×
1.2
×
4.0
×
10
4
10
9
10
4
10
2
- Ocean
3.9
×
1.2
×
2.3
×
1.0
×
- Earth's crust and
sediments
10
8
10
10
10
8
10
7
1.0
×
1.2
×
2.0
×
2.0
×
10
4
- Biosphere
<1
×
10
2
10
0
10
0
- Terrestrial plants
5.6
×
3.5
×
3.0
×
10
3
10
0
10
2
- Soils
1.5
×
9.5
×
1.0
×
10
3
- Fossil organic matter
4
×
Table 4.3.
Distribution, in different reservoirs of the outer envelopes of the Earth, of
four chemical elements that are discussed in detail in sections 4.3 to 4.6. Each value
represents the total mass of the element expressed in Pg C (10
15
grams) or Gt
(10
9
tons). The exploitable part of the phosphorus present in the lithosphere
represents only a millionth of the quantity of this element in the reservoir
Nitrogen, phosphorus, silicon, sulfur and iron are some of the
chemical elements required for growth by different types of marine
organism. Substances dissolved in seawater containing these essential
elements are called inorganic nutrients when their molecules do not
contain carbon-hydrogen bonds, and organic nutrients when their
molecules contain at least one such bond. Nutrients that are normally
present in seawater in micromolar concentration (µmol L
-1
) are called
macronutrients, and those which are usually present in nanomolar
concentration (nmol L
-1
) are called micronutrients.
4.3. Carbon: at the heart of living matter
Carbon is the chemical element at the heart of living matter. The
biomass of living organisms and the chemical compounds that come
from the decomposition of this biomass form the organic matter,
which is distinct from inorganic matter. The area of chemistry that
studies carbon compounds is called organic chemistry. A chemical
compound is said to be organic when one or more atoms of carbon are
