How different nitrogen fertilizers affect arsenic mobility in paddy soil after straw incorporation?

• Published in: Journal of hazardous materials 2022-08, Vol.436, p.129135-129135, Article 129135
• Main Authors: Liu, Lin, Shen, Rui-Lin, Zhao, Zhong-Qiu, Ding, Long-Jun, Cui, Hui-Ling, Li, Gang, Yang, Yu-Ping, Duan, Gui-Lan, Zhu, Yong-Guan
• Format: Article
• Language: English
• Subjects: Arsenic; Iron redox; Nitrogen; Paddy soil; Straw incorporation
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2022.129135

In straw return fields, nitrogen-fertilizers are added to mitigate microbial competition for nitrogen with plants. However, in arsenic (As)-contaminated paddy fields, the specific effects of different nitrogen fertilizers on As mobility after straw incorporation and the interactions among iron(Fe)/carbon(C)/nitrogen(N)/As are not well understood. In the reported microcosm experiment we monitored As-mobility as a function of different dosages of KNO3, NH4Cl and rice straw incorporation. Addition of both KNO3 and NH4Cl significantly inhibited the As mobilization induced by straw incorporation. Following the KNO3 addition, the As concentration in porewater dropped by 51–66% after 2 days of the incubation by restraining Fe reduction and enhancing Fe oxidation. High-dose NH4Cl addition reduced As in porewater by 22–43% throughout the incubation by decreasing porewater pH. High-throughput sequencing results demonstrated that KNO3 addition enriches both the denitrifying and Fe-oxidizing bacteria, while diminishing Fe-reducing bacteria; NH4Cl addition has the opposite effect on Fe-reducing bacteria. Network analysis revealed that As and Fe concentrations in porewater were positively correlated with the abundance of denitrifying and Fe-reducing bacteria. This study broadens our insight into the As biogeochemistry associated with the N/C/Fe balance in soil, which are of great significance for agronomic management and mitigation the risk of As-contaminated paddy fields. [Display omitted] •KNO3 immobilized As by enhancing Fe oxidation and restraining Fe dissolution.•NH4Cl immobilized As by decreasing soil pH and inhibiting anammox.•KNO3 enriched iron-oxidizing bacteria but reduced iron-reducing bacteria.•NH4Cl addition increased the relative abundance of iron-reducing bacteria.•KNO3 showed short-term but NH4Cl exhibited long-term As immobilization function.