湖北恩施渔塘坝自然硒的分布及其环境意义

自然硒在渔塘坝富硒碳质岩层及其附近的土壤、废弃“石煤”堆中广泛发育。渔塘坝自然硒的空间分布与富硒碳质岩层密切相关，其纵向分布整体与富硒碳质岩层的走向一致，局部地段呈片状或环带状；横向上沿着富硒碳质岩层的倾向方向，从二叠纪茅口组的碳质硅质岩层到吴家坪组的碳质页岩层，自然硒的发现由易到难。渔塘坝当前的地质环境有利于自然硒的形成和保存，且一旦在表生环境形成后将会在特殊的地段发生次生富集。但是，自然硒形成的地质环境一旦被人类活动打破，暴露于地表的自然硒也能够发生迅速的氧化而再次迁移，进入河流和当地居民的食物链系统。因此，渔塘坝及恩施地区广泛分布的富硒碳质岩层为硒中毒的发生提供了必要条件，当荒地开垦或开挖“石煤”等人类活动为自然硒的氧化和迁移提供充分条件时，硒中毒的发生仍将不可避免。

The Distribution of Native Selenium in Yutangba and Its Environmental Significance

Yutangba, where a sudden incidence of human selenosis occurred in 1963, is located in the northern part of Shuanghe community about 81 km SE of Enshi City, Hubei Province, China. In Yutangba, native Se extensively exists within Se-rich carbonaceous rocks, abandoned stone coal spoils and high-Se soils close to Serich carbonaceous strata. The distribution of native Se is parallel with Se-rich carbonaceous strata, with local circles or strips. Selenium particles become sparse from the Permian Maokou to Wujiaping formation along the dip. Native Se is probably the main dominance, and once formed, will be re-deposited in special sites such as near water table. However, when Se-rich stone coal removed from deep as a fuel or fertilizer, a large amount of native Se will be quickly oxidized again and transformed to soluble Se, which will be enriched in local food via water irrigation systems. So, Se-rich carbonaceous strata are a necessary condition for the incidence of Selenosis, and human cultivating manner and activities such as mining stone coal as a fuel or fertilizer will provide a sufficient condition for oxidation of elemental Se and its transportation. When soluble Se is accumulated to a certain extent and is under the suitable environmental condition, selenosis would occur again in some places of Enshi Prefecture.