Abstract:

The behavior of selenium, an important trace element for human and animal in environmental geochemistry, is described quantitatively based on the components of 58 certified reference materials collected as rocks, soils or stream sediments in China. The description equation on the relationship between the selenium contents and the corresponding chemical weathering indices is fitted as lgc=0.822×(1.2-WIG/100)-1.061×lg(K₂O/SiO₂)-2.704, where c is the content of selenium in μg/g, the value of WIG varies from 4.3 to 111.6, and the value of K₂O/SiO₂ varies from 0.020 to 0.137. This equation can be used to describe the geo-chemical background values of selenium resulted from different weathering degrees in rocks, soils, and stream sediments. Samples with strong weathering degrees have higher values of the selenium geochemical backgrounds commonly. The equation is applied to two districts of Hetai and Nankunshan in Guangdong Province, China. The results tell us that the areas with strong weathered geological bodies can be viewed as the candidates to find the areas with plentiful or rich selenium contents. The areas with plentiful or strong weathered geological bodies can be found feasibly based on the data of the Regional Geochemistry-National Reconnaissance (RGNR) project. In the soil evaluation on environmental quality, the plentiful or rich selenium areas can be assessed by the analyzed values of selenium. Furthermore,residual values which are the deduction results of geochemical background values from their analyzed values can be used to determine the plentiful or rich selenium geological bodies underlying the weathered materials. In other words, the geological bodies with plentiful or rich selenium which are underlying the weathered soils can be determined feasibly based on the data of the Multi-Purpose Regional Geochemical Survey project. The case study on the Nankunshan district indicates that the middle and west part of the Nankunshan pluton must be plentiful or rich in selenium.

Key words: certified reference material, geochemical background value, chemical weathering index, Hetai, Nankunshan, Guangdong Province