This study mechanistically addressed for the first time, the contradiction between the application of many biochars to paddy soil and increased arsenic (As) release as employed by most of previous studies. Three types of biochar containing natural and chemical forms of Si: (i) unmodified rice husk biochar (RHBC), (ii) RHBC modified with Si fertilizer (Si-RHBC), and (iii) RHBC modified with nanoparticles of montmorillonite clay (NM-RHBC) were applied in As-contaminated paddy soil to examine their potential to control the mobility of As in the soil-microbe-rice system. Both Si-RHBC and NM-RHBC decreased As concentration in porewater by 40–65 %, while RHBC decreased by 30–44 % compared to biochar unamended soil from tillering to maturing stage. At tillering stage, RHBC, Si-RHBC and NM-RHBC amendments significantly decreased As(III) concentration in the rice rhizosphere by 57, 76 and 73 %, respectively compared to the control soil. The immobilization of As is due to: (i) lowering of microbe mediated As release from iron minerals, (ii) oxidation of As(III) to As(V) by aioA gene, and (iii) adsorption on a Si-ferrihydrite complex. The decrease of more toxic As(III) and its oxidation to less mobile As(V) by Si-rich biochar amendments is a promising As detoxification phenomenon in the rice rhizosphere.
Bibliographical noteFunding Information:
This research was financially supported by the Natural Science Foundation of China (grant no. 21661132001 ). We also sincerely thank Mrs. Jane Macarthur, Ricegrowers Limited, Trading as SunRice, New South Wales 2705, Australia for providing rice husk biomass for this work.
© 2020 Elsevier B.V.
- High-throughput sequencing
- Montmorillonite clay
- Rice-husk biochar
- Silica transporter
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- Waste Management and Disposal
- Health, Toxicology and Mutagenesis