The Influence of Geochemistry on Biological Diversity in Fennoscandia and Estonia

The Earth’s crust is predominantly composed of a relatively small number of chemical elements. Only eight of them: oxygen, silicon, aluminum, iron, calcium, magnesium, sodium and potassium are present in amounts exceeding one weight percent and together they comprise almost 99% of the entire crust [1, 2]. Some elements are exceedingly rare in the Earth, or have short-lived radioactive isotopes. For example, promethium (Pm) occurs in the crust in only very small concentrations in certain uranium ores, being produced as result of nuclear fission, with the longest-lived isotope having a half-life of only 17.7 years. Similarly, technetium is a relatively light radioactive metal with atomic number 43, having no stable isotopes, while the longest-lived radioactive isotope (Te-98) has a half-life of 4.2 million years. Technetium only occurs naturally, in trace amounts, in uranium ores produced by nuclear fission [3]. When such elements are excluded, there remain 90 naturally occurring chemical elements [4] to form the geochemical basis of the life of the Earth.