论文部分内容阅读
本文概述了硒的物理、化学性质 ,形态和存在形式以及硒的地球化学循环和富集作用。硒呈四种主要的无机形态存在于自然界中 :硒化物 ( -2价 )、元素硒 ( 0价 )、亚硒酸盐 ( +4价 )和硒酸盐 ( +6价 )。不同硒形态的存在 ,很大程度上取决于 pH和Eh条件。硒的天然的、总的地球化学循环主要涉及壳岩源和海洋沉积物。次一级的循环涉及其它无机源和沉积物。另外 ,整个硒的壳循环 (岩石圈、生物圈、水圈和大气圈 )也强烈受到生物化学反应的影响 ,这些反应使硒在有机组分中固定或迁移。人类活动向环境中排放的硒极大地改变了硒天然的地球化学循环 ,主要是煤的燃烧、硫化物矿床的开采及工业上利用硒所产生的废料。岩浆期后热液活动阶段是硒最主要的活动、富集阶段 ,硒能大量地呈分散形式 (类质同像 )或独立矿物形式存在于这一阶段中 ;在火山及喷气活动产物 (有关热泉 )中硒的富集程度也很高。另外 ,硒在页岩特别是海相黑色页岩中的富集作用与生物活动有密切的关系。
This paper summarizes the physical, chemical, morphological and existent forms of selenium and the geochemical cycle and enrichment of selenium. Selenium exists in nature in four major inorganic forms: selenide (-2), elemental selenium (0), selenite (+4) and selenate (+6). The existence of different selenium forms depends to a large extent on the pH and Eh conditions. The natural, total geochemical cycles of selenium are mainly related to the source of crustal rocks and marine sediments. Sub-cycle involves other inorganic sources and sediments. In addition, the entire selenium shell cycle (lithosphere, biosphere, hydrosphere, and atmosphere) is also strongly influenced by biochemical reactions that cause selenium to be immobilized or migrated in organic components. Selenium emitted from the human activities to the environment has greatly changed the natural geochemical cycle of selenium, mainly from the burning of coal, the extraction of sulfide deposits and the industrial production of selenium. After the magmatic stage, the hydrothermal activity stage is the most important activity of selenium. During the enrichment stage, selenium can exist in this stage in a large amount in the form of disperse (isomorphic) or independent minerals. In the volcano and jet products Hot Springs) selenium enrichment level is also high. In addition, the enrichment of selenium in shale, especially marine black shale, is closely related to biological activities.