Geoscience Reference
In-Depth Information
4
Marine Biogeochemical Cycles
4.1. Introduction: geochemistry, biogeochemistry and marine
biogeochemistry
4.1.1.
Geochemistry and cosmochemistry
Geochemistry [JAM 09] forms part of the Earth Sciences. This
discipline focuses on the chemical composition of the Earth and its
constituents, in particular rocks and minerals, and aims to understand
the cycles within which most chemical elements naturally present on
our planet (there are over one hundred of them) and some of their
components (e.g. water and carbon dioxide) circulate between the
reservoirs that form the outer envelopes (or spheres) of the Earth.
These reservoirs are the Earth's crust, the hydrosphere (which
includes the oceans), the atmosphere and the biosphere
1
.
We will not consider the interior of the Earth in this chapter,
because its constituents (core and mantle) do not directly interact with
the outer envelopes. Table 4.2 shows that the main chemical elements
are not the same in the Earth's crust, the seawater and the atmosphere.
Geochemistry also focuses on the origins and evolution of
chemical elements in the Universe, especially in the Solar System
since this is where the Earth can be found. Here, geochemistry
1 Abbreviations and special symbols are summarized in Table 4.1.
