Key Takeaways & Executive Findings
- •• • DGT-measured Se content most accurately reflected soil Se bioavailability, outperforming three traditional extraction methods; 96.7% of soil samples and 66.7% of rice samples met selenium-rich standards, validating DGT's predictive power for practical soil management. • • Bioconcentration factor (BCF) analysis revealed that Se primarily enriched in rice roots rather than grains, indicating low grain Se accumulation efficiency; this necessitates targeted agronomic strategies to enhance grain Se content. • • Correlation analysis identified soil pH, organic matter (SOM), cation exchange capacity (CEC), and sulfur (S) content as key factors influencing Se bioavailability; adjusting these parameters can effectively improve Se uptake, offering actionable levers for soil amendment. • • DGT technology accounts for dynamic resupply from solid phase to solution, overcoming limitations of static equilibrium-based extraction methods; this dynamic simulation of plant uptake provides more reliable risk assessment and resource evaluation.
Abstract
Selenium (Se) is an essential trace element for mammals, yet no universally applicable method exists for assessing soil Se bioavailability. This study validated the feasibility of diffusive gradients in thin-films (DGT) technology for accurately evaluating Se bioavailability in paddy soils under natural conditions, and analyzed Se migration in the soil-plant system, soil kinetic characteristics, and the influence of physicochemical properties on Se bioavailability. Rice plants and corresponding rhizosphere soil samples were collected and analyzed using three traditional extraction methods alongside DGT. Results showed that 96.7% of soil samples and 66.7% of rice samples met the selenium-rich standard, and Se content measured by DGT most accurately reflected soil Se bioavailability. The bioconcentration factor (BCF) of different rice plant parts indicated generally low Se enrichment in grains, with primary enrichment in rice roots. Correlation analysis revealed that adjustments in soil pH, organic matter (SOM), cation exchange capacity (CEC), and sulfur (S) content could effectively improve soil Se bioavailability. These findings underscore DGT's superiority over conventional extraction methods for predicting Se uptake, offering a robust tool for managing selenium-rich agricultural resources.
1. Introduction
Conventional assessment of soil selenium (Se) bioavailability relies on single-step or sequential chemical extractions, which operate under equilibrium assumptions and often fail to capture the dynamic resupply of Se from solid to solution phases during plant uptake. This static approach leads to significant discrepancies between measured available Se and actual plant Se content, as exemplified by cases where total soil Se is high but bioavailable Se is low. The lack of a standardized method hampers the development of selenium-rich agriculture and accurate risk assessment.
Diffusive gradients in thin-films (DGT) technology offers a dynamic alternative by simulating root-induced flux and continuously measuring labile Se species. This study directly compares DGT with three traditional extraction methods in naturally enriched paddy soils, demonstrating that DGT-measured Se provides the most accurate prediction of rice Se content. By integrating soil physicochemical properties, the research identifies key factors controlling Se bioavailability, providing a scientific basis for optimizing soil management to enhance Se accumulation in crops.
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YAO Yuxue, ZHENG Liugen (2026). Evaluation of Selenium Bioavailability in Naturally Enriched Paddy Soils Based on Diffusive Gradients in Thin Films (DGT) and Its Influencing Factors. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025041805
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Frequently Asked Questions
How does DGT outperform traditional extraction methods in predicting selenium uptake by rice?
DGT measures the dynamic flux of Se from soil solid phase to solution, simulating root uptake, whereas traditional methods (e.g., single-step and sequential extractions) rely on equilibrium partitioning and often over- or under-estimate available Se. In this study, DGT-measured Se showed the strongest correlation with rice Se content, with 96.7% of soil samples meeting Se-rich standards, indicating its superior predictive accuracy.
What are the key soil parameters that influence selenium bioavailability, and how can they be managed?
Soil pH, organic matter (SOM), cation exchange capacity (CEC), and sulfur (S) content were significantly correlated with Se bioavailability. Adjusting these parameters—e.g., liming to raise pH, adding organic amendments, or managing S fertilization—can enhance Se availability. However, optimal ranges must be determined locally, as excessive S may compete with Se for plant uptake.
Why does selenium primarily accumulate in rice roots rather than grains, and what implications does this have for human nutrition?
The bioconcentration factor (BCF) analysis showed higher Se enrichment in roots than grains, indicating limited translocation to edible parts. This suggests that while soil Se may be sufficient, grain Se levels may still be suboptimal for human dietary needs. Agronomic biofortification strategies, such as foliar Se application or breeding for enhanced translocation, may be necessary.
Can DGT be applied to other crops and soil types for selenium bioavailability assessment?
DGT has been successfully used for various elements (e.g., Cd, Zn, As) and crops (e.g., wheat, maize). This study extends its application to paddy rice in naturally enriched soils. However, calibration is required for different soil conditions and plant species, as DGT response depends on soil properties and root physiology.
What are the practical implications of this study for selenium-rich soil resource management?
The findings provide a reliable method (DGT) for identifying soils with high Se bioavailability, enabling targeted use of selenium-rich soils for producing high-Se crops. Additionally, understanding the influence of soil properties allows for soil-specific management practices to optimize Se uptake, thereby improving agricultural value and human nutrition.
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