Abstract: To evaluate the bioavailability of selenium in selenium-rich soil of Yinan, Shandong Province in different crops, and to speculate its source, soil, plant, and rock samples were collected accordingly from the research area, then the total   selenium content in each sample and the content  of five forms of selenium in water-soluble, weak acid extracted, reducible, oxidizable, and residual states were tested by ICP-MS, and the results were compared and analyzed. The results showed that: the total selenium content in soil is significantly constrained by spatial location and water system constraints; The effective selenium content  is positively correlated with the total selenium content, and the spatial distribution is consistent; The total selenium content in soil is positively correlated with the nitrogen and phosphorus content; The main form of selenium in soil is selenite. The fruits of three crops, peanuts, walnuts, and watermelons, grew on selenium-rich soil in the research area are enriched with selenium element. The selenium source in selenium-rich soil is related to shale, mudstone, and upstream iron ore in the regional strata, and it is speculated that the above rocks were weathered into soil and later transported to the clay and sandy clay areas by water flow, where they were adsorbed and deposited by soil clays to form selenium-rich areas.

Key words: Yinan, soil, plant, selenium, bioavailability