Selenium in certain Finnish sediments

Almost 100 sediments, mostly Finnish, have been analyzed for selenium. Tentative values for the average selenium contents of the various groups are given. The distribution of the element in the sediments studied is interpreted as follows. During weathering of selenium-bearing sulphides, Eh-pH conditions favor liberation of elemental selenium, which is then adsorbed and concentrated in clays and organic colloids. Residual sediments contain mostly feldspar and quartz and are devoid of selenium; their specific content depends on the colloids and fine clayey fractions present. Cultivation appears to increase selenium content, this increase being particularly noticeable in peat soils, which originally contain very little selenium.