Geochemical Characteristics of Selenium in Surface Soil of Central Townships in Zhaojue County, Sichuan Province

Selenium (Se) is one of the essential trace elements for humans, and an important way for humans to obtain and supplement selenium is by eating natural selenium-enriched agricultural products. The geochemical characteristics of selenium in the survey area are an important basis for the effective utilization of selenium-enriched land resources and the development of selenium-enriched agricultural and sideline products.

To investigate the geochemical characteristics of selenium content, distribution and influence factors in the study area.

Soil and crop samples were collected from a central village of Zhaojue County, Sichuan Province. AFS, XRF and ICP-MS were used to determine the contents of elements including Se, Al₂O₃, TFe₂O₃, SiO₂, OrgC, and pH values. Geochemical characteristics of selenium content, distribution and influencing factors in the study area were investigated using statistical and correlation analysis.

(1) The soil selenium content in the study area ranged from 0.04 to 1.50mg/kg, with an average value of 0.33mg/kg. The delineated selenium-enriched soil area was 7.23km², accounting for 30.31% of the total soil area. The selenium content of the soil developed in basalt was the highest, with an average of 0.4mg/kg, indicating that the geological background in the area was closely related to the soil selenium content. The Se-enriched soil in the area was mainly controlled by the Emeishan basalt Formation, which contained basalt intercalating with picrite and tuffaceous sand and mudstone. (2) The enrichment capacity of selenium varied in different land utilization and soil types. The absorption capacity of selenium in soil decreased due to human agricultural activities. Clayey particles or iron oxides in the yellow-brown loam layer were easy to combine and enrich selenium. The selenium content in acidic soil was inversely correlated to pH value. There was a significant positive correlation between soil organic matter and selenium content. Soil texture had a certain effect on selenium content. (3) Corn and potatoes from selenium-enriched soils had very low selenium content.

During the exploitation and utilization of selenium-enriched soil, organic fertilizer should be added in time and soil pH should be adjusted in agricultural areas such as dry land and paddy field, and other agricultural products should be developed by using selenium-enriched resources.