Sediment arsenic remediation by submerged macrophytes via root-released O2 and microbe-mediated arsenic biotransformation

• Published in: Journal of hazardous materials 2023-05, Vol.449, p.131006-131006, Article 131006
• Main Authors: Li, Cai, Ding, Shiming, Ma, Xin, Wang, Yan, Sun, Qin, Zhong, Zhilin, Chen, Musong, Fan, Xianfang
• Format: Article
• Language: English
• Subjects: Aquatic plants; Arsenic cycling; Iron plaque; Phytoremediation; Sediment
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2023.131006

Arsenic (As)-contaminated water restoration is extremely challenging because As remobilization from sediments can result in episodic or long-term release of As to the overlying water. In this study, by combining high-resolution imaging techniques with microbial community profiling, we examined the feasibility of utilizing the rhizoremediation of submerged macrophytes (Potamogeton crispus) to decrease As bioavailability and regulate its biotransformation in sediments. Results showed that P. crispus considerably decreased the rhizospheric labile As flux to lower than 4 pg cm−2 s−1 from larger than 7 pg cm−2 s−1, suggesting its effectiveness in promoting As retention in sediments. Iron plaques induced by radial oxygen loss from roots decreased the mobility of As by sequestering it. Additionally, Mn-oxides may act as an oxidizer for the oxidation of As(III) to As(V) in the rhizosphere, which can further increase the As adsorption owing to the strong binding affinity between As(V) and Fe-oxides. Furthermore, microbially mediated As oxidation and methylation were intensified in the microoxic rhizosphere, which decreased the mobility and toxicity of As by changing its speciation. Our study demonstrated that root-driven abiotic and biotic transformation contribute to As retention in sediments, which lays a foundation for applying macrophytes to the remediation of As-contaminated sediments. [Display omitted] •Abiotic and biotic oxidation of Fe(II) promoted the formation of Fe plaques.•Fe plaque sorption decreased the bioavailability of As in the rhizosphere.•Oxidation of As(III) was promoted by Mn-oxides and aioA gene-related bacteria.•Activity of microbial communities involved in As methylation was elevated.