寒冷地区 Mollisol 稻田湿地硒的流失：来自流通式反应器实验和基于过程的建模的见解,Environmental Science & Technology

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寒冷地区 Mollisol 稻田湿地硒的流失：来自流通式反应器实验和基于过程的建模的见解
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2023-04-07 , DOI: 10.1021/acs.est.3c00011
Kunfu Pi _{1,

2,

3,

4} , Philippe Van Cappellen _{3,

5} , Lei Tong _{1,

2,

4} , Yiqun Gan _{1,

2} , Yanxin Wang _{1,

2}

Affiliation

Mollisols 是确保全球粮食供应的重要农业资源。由于其对健康的重要性，硒 (Se) 在 Mollisol 中的命运引起了越来越多的关注。从传统旱地到稻田湿地的土地利用变化影响了脆弱的 Mollisol 农业生态系统中硒的生物利用度。然而，潜在的过程和机制仍然难以捉摸。在这里，使用北部寒冷地区的稻田 Mollisol 进行的流通式反应器实验结果表明，连续 48 天的地表水淹没导致氧化还原区带化，使 Mollisol Se 损失高达 51%。进一步基于过程的生物地球化学模型表明，在 30 厘米深的 Mollisol 中，溶解有机物 (DOM) 的降解率最高，其中含有最高水平的不稳定 DOM 和有机结合硒。含硒 DOM 降解引起的电子分流与吸附硒的铁氧化物的还原溶解相结合，主要是导致 Se(IV) 释放到孔隙水中的原因。DOM 分子组成的随之发生的变化使有机结合的硒储层易受水淹引起的氧化还原区带化的影响，并可能通过破坏硫醇化硒和从 Mollisol 层排放气态硒而增加硒的损失。这项研究强调了一个被忽视的情景，即稻田湿地中生物可利用硒的物种形成驱动损失可能是寒冷地区 Mollisol 农业生态系统的重大后果。DOM 分子组成的随之发生的变化使有机结合的硒储层易受水淹引起的氧化还原区带化的影响，并可能通过破坏硫醇化硒和从 Mollisol 层排放气态硒而增加硒的损失。这项研究强调了一个被忽视的情景，即稻田湿地中生物可利用硒的物种形成驱动损失可能是寒冷地区 Mollisol 农业生态系统的重大后果。DOM 分子组成的随之发生的变化使有机结合的硒储层易受水淹引起的氧化还原区带化的影响，并可能通过破坏硫醇化硒和从 Mollisol 层排放气态硒而增加硒的损失。这项研究强调了一个被忽视的情景，即稻田湿地中生物可利用硒的物种形成驱动损失可能是寒冷地区 Mollisol 农业生态系统的重大后果。

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

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.

更新日期：2023-04-07

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