Yankuang ceshi (Jan 2020)
Geochemical Characteristics of Selenium in Rocks from the Western Sichuan Plateau
Abstract
BACKGROUND Studies on soil, water and other media in the Western Sichuan Plateau show that the selenium content in this area is very low. The selenium concentrations of the natural soil profile, surface soil, sediment, surface water, and groundwater are 0.06-0.16μg/g, 0.075-0.204μg/g, 0.069-0.310μg/g, nd-0.096μg/L and nd-0.058μg/L, respectively, which are all lower than the average selenium content in the corresponding environmental media in China, affecting the health of local people. OBJECTIVES To explore the geochemical characteristics of selenium in rocks in the study area and to find the influencing factors for low selenium in rocks. METHODS Eighty rock samples were collected from the Western Sichuan Plateau, and six core samples were collected at the same time. These samples were mainly slate, sandstone, limestone and shale. Atomic fluorescence spectrometry (AFS) was used to determine the selenium content, and the geochemical characteristics of selenium in rocks and core samples in the Aba area of the Western Sichuan Plateau were studied. RESULTS The selenium content of rocks ranged from 0.030 to 0.282μg/g, with an average value of 0.09μg/g, which was lower than the crustal abundance of selenium. The content of selenium in different types of rocks was:shale > limestone > slate > sandstone. The selenium content in the rock also showed large differences in different regions:Songpan > Aba > Land Pond > Maerkang > Jiuzhaigou > Ruoergai > Hongyuan, which may be caused by rock type, organic matter and geological environment. The minimum, maximum and average selenium content in each section of the core was 0.02-0.07μg/g, 0.21-0.34μg/g and 0.06-0.17μg/g, respectively. Moreover, the selenium content of each borehole was significantly lower than the crustal abundance of selenium. CONCLUSIONS The distribution of selenium in rocks is significantly affected by organic matter, lithology and rock compactness. Low selenium in rocks is mainly due to low selenium in environmental media in Western Sichuan.
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