This study examined the role of intermittent illumination/dark conditions coupled with MnO₂-ammendments to regulate the mobility of As and Fe in flooded arsenic-enriched soils. Addition of MnO₂ particles with intermittent illumination led to a pronounced increase in the reductive-dissolution of Fe(III) and As(V) from flooded soils compared to a corresponding dark treatments. A higher MnO₂ dosage (0.10 vs 0.02 g) demonstrated a greater effect. Over a 49-day incubation, maximum Fe concentrations mobilized from the flooded soils amended with 0.10 and 0.02 g MnO₂ particles were 2.39 and 1.85-fold higher than for non-amended soils under dark conditions. The corresponding maximum amounts of mobilized As were at least 92 % and 65 % higher than for non-amended soils under dark conditions, respectively. Scavenging of excited holes by soil humic/fulvic compounds increased mineral photoelectron production and boosted Fe(III)/As(V) reduction in MnO₂-amended, illuminated soils. Additionally, MnO₂ amendments shifted soil microbial community structure by enriching metal-reducing bacteria (e.g., Anaeromyxobacter, Bacillus and Geobacter) and increasing c-type cytochrome production. This microbial diversity response to MnO₂ amendment facilitated direct contact extracellular electron transfer processes, which further enhanced Fe/As reduction. Subsequently, the mobility of released Fe(II) and As(III) was partially attenuated by adsorption, oxidation, complexation and/or coprecipitation on active sites generated on MnO₂ surfaces during MnO₂ dissolution. These results illustrated the impact of a semiconducting MnO₂ mineral in regulating the biogeochemical cycles of As/Fe in soil and demonstrated the potential for MnO₂-based bioremediation strategies for arsenic-polluted soils.

这项研究探讨了间歇照明/黑暗条件与MnO _2-修饰物一起调节富砷土壤中As和Fe迁移率的作用。与相应的黑暗处理相比，添加间歇照明的MnO ₂颗粒可显着提高水淹土壤中Fe（III）和As（V）的还原溶解度。较高的MnO ₂剂量（0.10对0.02 g）显示出更大的效果。在49天的孵化过程中，从淹没土壤中调出的最大铁浓度用0.10和0.02 g MnO ₂修正在黑暗条件下，土壤颗粒比未改良土壤高2.39倍和1.85倍。在黑暗条件下，相应的最大迁移量分别比未改良土壤高出至少92％和65％。土壤腐殖质/富里叶酸化合物清除激发空穴增加了矿物光电子的产生，并促进了MnO ₂改良的光照土壤中Fe（III）/ As（V）的减少。此外，MnO的₂修正由富集金属还原菌（例如，移位土壤微生物群落结构Anaeromyxobacter，芽孢杆菌和地杆菌）和增加Ç型细胞色素生产。微生物对MnO _2的响应该修正促进了直接接触细胞外电子转移过程，从而进一步增强了Fe / As的还原。随后，释放的Fe（II）和As（III）的迁移率通过在MnO ₂溶解过程中在MnO ₂表面产生的活性位上的吸附，氧化，络合和/或共沉淀而部分减弱。这些结果说明了半导体MnO ₂矿物对调节土壤中As / Fe的生物地球化学循环的影响，并证明了基于MnO ₂的砷污染土壤生物修复策略的潜力。