Selenium crustal abundance

The average crustal abundance of selenium is 0.05mgkg (Jacobs, 1989). Like arsenic, selenium is strongly chalcophile and is partitioned into sulfides and rare selenides, such as... 

The primary sources of selenium are volcanic emanations and metallic sulfides associated with igneous activity. Secondary sources are biological sinks in which it has accumulated. The selenium content of black shales, coal, and petroleum is 10-20 times the crustal abundance (0.05 ppm). Seleniferous black shales are the parent materials of the widespread seleniferous soils of the western plains of the United States. When burned, coal and petroleum containing selenium give rise to a redistribution of particulate Se and SeOg. The average selenium content of U. S. coal is about 3 ppm and of petroleum about 0.2 ppm. Selenium is an essential nutrient for animals and is required at a concentration of about 40 ppb in their diet at concentrations of 4000 ppb and above, however, it becomes toxic to animals. 

The selenium contents of two Japanese coals were 1.3 and 1.05 ppm (24). The selenium content of 86 samples of coal (25) from 55 counties in 20 states of the United States (Table V) averaged 3.3 ppm and ranged from 0.46 to 10.65 ppm. Only three values were less than 1 ppm. With a crustal abundance of only 0.05 ppm these coals contain 10-200 times as much selenium as is found in igneous rocks. 

The crustal abundance of selenium is estimated to be 0.05 ppm. Analyzed igneous rocks contain 0.004r-1.5 ppm selenium. 

Although the differences in physical and chemical properties of selenium and sulfur tend to separate these elements in weathering and erosion, their similar functions in biological reactions tend to unite them in organic-rich materials. Selenium is found often manyfold its crustal abundance in black organic-rich shales, in coal, and, to a lesser extent, in petroleum. 

Fig. 2. Periodic table indicating relative abundance and biological importance of elements. Highlighted elements are the 30 most abundant crustal elements with concentrations ranging from 46 % for oxygen to 0.1 yg/g for selenium. Bold faced elements have known biological functions with indicating limited data and controversy. Data taken from Wood and Wang, 1983.

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