Yankuang ceshi (Nov 2019)
Distribution Characteristics and Sources Identification of Selenium-rich Soils in the Ecological Conservation Area of the Daqinghe River Watershed, Beijing
Abstract
BACKGROUND Beijing is a typical geographical distribution area of selenium deficiency. However, some research results in recent years indicate that the soils in some areas reaches the level of selenium enrichment. It is important to study the characteristics of selenium distribution in these areas for the research of a selenium-rich environment in Beijing and the development of selenium-rich land resources. OBJECTIVES To discuss the characteristics of selenium content in soil and crops, the source of selenium and the relationship between selenium in soil and other elements such as carbon, iron and phosphorus, and to evaluate the safety of selenium-rich land. METHODS Samples of 1297 topsoil, 25 sets of corn and corresponding root soil and 15 rock samples were collected from an eco-conserving division of the Daqinghe River watershed. The content of selenium in these samples was determined by atomic fluorescence spectrometry. Methods of correlation analysis and multivariate statistical analysis and GIS technology were used to study the characteristics of selenium content in soil and crops, the source of selenium enrichment, and the relationship between soil selenium and other elements such as carbon, nitrogen, phosphorus and sulfur, and the safety of selenium-rich land was evaluated. RESULTS The results showed that the soil selenium content ranged from 0.055 to 0.465mg/kg and that the background value was 0.257mg/kg, which show selenium-rich characteristics. 360.4km2 selenium-rich land resources was identified. The selenium content of corn ranged from 0.028 to 0.70mg/kg, and the geometric mean was 0.20mg/kg. 80% of the corn samples were selenium-rich products. The selenium-rich soil and the selenium-rich crops had the same spatial distribution, which indicated that the soil was an important source of selenium in crops. CONCLUSIONS Geological background and soil parent material are the key control factors affecting the distribution of selenium-rich land resources. Dark rock series of fluvial deposition are a crucial source of selenium in soil. The overall environmental quality of selenium-rich land is clean and safe, and only 0.2% of the area (3.23km2) contains soil heavy metal (Cd, Hg, Pb) content, which exceeds the level of risk management control. Due to these findings, attention needs to be paid during selenium-rich land development.
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