Selenium distribution in cultivated Argosols and Gleyosols of dry and paddy lands: A case study in Sanjiang Plain, Northeast China

Loss of Selenium from Mollisol Paddy Wetlands of Cold Regions: Insights from Flow-through Reactor Experiments and Process-Based Modeling

“…Further degradation of Se-bearing DOM coupled to the reductive dissolution of Fe oxides, may have migrated Se into the pore water, which under the flooding condition, can facilitate Se leaching. This probably represents the most dynamic part of Mollisol Se migration that may vary seasonally but was undervalued previously. ,, Therefore, the biogeochemical cycle of Se may have been altered significantly in the Mollisol paddy wetlands.…”

“…Note that the content of total Se in the world’s soils is highly variable (<0.1 to >1000 mg/kg), while an average of approximately 0.40 mg/kg was frequently documented . In China, however, the average soil Se content was only 0.17 mg/kg, but it reached approximately 0.68 mg/kg in the paddy soils of Se-rich area. , Approximately half of the world’s population rely upon paddy rice for sustenance, and paddy rice accounts for a significant portion of their daily intake of proteins and micronutrients including Se . Because a large population is still faced with Se-deficiency problems, an efficient management of Se resource in the Mollisol agroecosystems has been a prime concern in commodity grain production.…”

“…This probably represents the most dynamic part of Mollisol Se migration that may vary seasonally but was undervalued previously. 3,6,7 Therefore, the biogeochemical cycle of Se may have been altered significantly in the Mollisol paddy wetlands.…”

“…Because Mollisols are an important host of dietary Se sources, the bioavailability and dynamics of Se in the Mollisols affect directly the quality of crop food produced . It is already known that Se bioavailability differs significantly between the dryland and paddy soils. , Land use change from conventional drylands to the current paddy wetlands can alter both structure (e.g., loss of stable aggregates) and physical–chemical–biological conditions of the Mollisol vadose zone. , For instance, the cultivated Mollisols suffer from soil acidity and redox shift that are companied by variations in the functional microbial community mediating redox zonation and nutrient release. , These factors affect directly the adsorption and redox transformation of Se species . In the context of global warming which impacts the cold regions disproportionately, these agricultural interventions make the Mollisols and Se in them prone to soil erosion, dehumification, and anthropogenic flooding. , Behind these changes is the increased potential of Se mobilization from the Mollisol layers, which are marginal or only moderately sufficient in Se. , Consequences for the bioavailability and sustainability of Se in the Mollisol agroecosystems, as well as the underlying processes and controlling mechanisms, however, remain to be elucidated.…”

“…3 It is already known that Se bioavailability differs significantly between the dryland and paddy soils. 6,7 Land use change from conventional drylands to the current paddy wetlands can alter both structure (e.g., loss of stable aggregates) and physical−chemical− biological conditions of the Mollisol vadose zone. 5,8 For instance, the cultivated Mollisols suffer from soil acidity and redox shift that are companied by variations in the functional microbial community mediating redox zonation and nutrient release.…”