Abstract:

Yutangba village, located in the northern part of Shuanghe Town of Enshi City in the SW of Hubei Province, China, is the unique location in the world where a sudden incidence of Se poisoning took place in 1963. It is one of the most typical high-Se areas in Enshi Prefecture, and thus it is selected as our study area. The results from studies show that native Se, which varies morphologically due to different mechanisms, has been discovered within the abandoned stone coal spoils and Se-rich carbonaceous siliceous rock. Krutaite(CuSe₂), mandarinoite(Fe₂(SeO₃)₃) and other Se minerals are also found. In the black Se-rich rocks of Yutangba, Refractory-Se and Organic-Se are predominant, the others are sulfide or selenide-Se, elemental Se and available Se, respectively. The processes of forming elemental Se is not only the key phase for Se transforming among the different Se fractions in Se-rich rocks, and also for Se releasing, mobilizing and transporting during Se-rich rocks weathering. The Se-rich carbonaceous siliceous rock and carbonaceous shale of the Permian Maokou and Wujiaping are the predominant factors for Yutangba to develop into a high-Se area. The manners of cultivating activities and life of local inhabitants are the main factors that cause Se to accumulate in food chain, and high risk of Se poisoning occurrence is mainly controlled by Se content in corn (main food). So, Yutangba is still a high risk area to villagers, where Se poisoning is possible to take place.

Key words: modes of occurrence of Se, native Se, Cu-Fe selenides, Se fractionation, black Se-rich rocks, local environment effect, Yutangba of Enshi