Loss of Selenium from Mollisol Paddy Wetlands of Cold Regions: Insights from Flow-through Reactor Experiments and Process-Based Modeling.
Environ Sci Technol
; 57(15): 6228-6237, 2023 04 18.
Article
in En
| MEDLINE
| ID: mdl-37026466
ABSTRACT
Mollisols are critical agricultural resources for securing global food supply. Due to its health importance, selenium (Se) fate in the Mollisols attracts growing concerns. Land use change from conventional drylands to paddy wetlands impacts Se bioavailability in the vulnerable Mollisol agroecosystems. The underlying processes and mechanisms however remain elusive. Here, results of flow-through reactor experiments with paddy Mollisols from northern cold-region sites indicate that continuous flooding with surface water for 48 d induced redox zonation that facilitated the loss of Mollisol Se by up to 51%. Further process-based biogeochemical modeling suggests largest degradation rates of dissolved organic matter (DOM) in 30 cm deep Mollisols that contained the highest-level labile DOM and organic-bound Se. Electron shunting from degradation of Se-bearing DOM coupled to reductive dissolution of Se-adsorbed Fe oxides accounts mainly for Se(IV) release into the pore water. Consequent changes in DOM molecular composition make the reservoir of organic-bound Se vulnerable to flooding-induced redox zonation and likely enhance Se loss through destruction of thiolated Se and emission of gaseous Se from the Mollisol layer. This study highlights a neglected scenario where the speciation-driven loss of bioavailable Se from the paddy wetlands can be a significant consequence in the cold-region Mollisol agroecosystems.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Selenium
Language:
En
Journal:
Environ Sci Technol
Year:
2023
Document type:
Article