ABSTRACT
The distribution of selenium (Se) in the topical environment is extremely variable with large regional differences (Tan 1991). During Earth’s geological periods of 4.6 billion years, various types of rocks and sediments were formed on surface of Earth, which were deposited during various geological periods. In the surface environment of China’s mainland, the true Quaternary Holocene sediments account for about 20% of the sediments (Ma & Liu 2002, Deng 2007), while the present sediments are mainly distributed along the coastal rivers, modern riverbeds, Aeolian deposits at the bottom of lakes, and in the modern desert. Nearly 80% of the land surface are covered by ancient rocks and sediments deposited during the geological periods, especially in the mountainous, hilly, and highland areas, which have been weathered in a denuded surface environment. Hence, the surface environment has inherited variability.
