pH dependence of arsenic speciation in paddy soils: The role of distinct methanotrophs

Zhao Feng Yuan, Yu Jie Zhou, Lina Zou, Zheng Chen, Williamson Gustave, Dechao Duan, Andreas Kappler, Xianjin Tang*, Jianming Xu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Arsenic (As) is a priority environmental pollutant in paddy field. The coupling of arsenate (As(V)) reduction with anaerobic methane (CH4) oxidation was recently demonstrated in paddy soils and has been suggested to serve as a critical driver for As transformation and mobilization. However, whether As(V)-dependent CH4 oxidation is driven by distinct methanotrophs under different pH conditions remains unclear. Here, we investigated the response of As(V)-dependent CH4 oxidation to pH shifts (pH 5.5–8.0) by employing isotopically labelled CH4. Furthermore, the underlying mechanisms were also investigated in well-controlled anoxic soil suspension incubations. Our results showed that As(V)-dependent CH4 oxidation is highly sensitive to pH changes (1.6–6.8 times variation of arsenite formation). A short-term (0–10 d) pH shift from near-neutral pH to acidic conditions (i.e., pH 5.5, −85% arsenite formation) had an inhibitory effect on As(V)-dependent CH4 oxidation. However, prolonged acidic conditions (i.e., >15 d) had no significant influence on As(V)-dependent CH4 oxidation. The microbial analyses indicated that As reduction in paddies can be driven by anaerobic CH4 oxidation archaea (ANME) and methanotrophs. And, methanotrophs may serve as a critical driver for As(V)-dependent CH4 oxidation. Moreover, type I methanotrophs Methylobacter were more active in oxidizing CH4 than type II methanotrophs Methylocystis when the pH ≥ 6.5. However, Methylocystis had a higher tolerance to soil acidification than Methylobacter. This study illustrates that As(V)-dependent CH4 oxidation could be dominated by distinct methanotrophs along with pH shifts, which eventually enhances As release in paddy soils.

Original languageEnglish
Article number120880
JournalEnvironmental Pollution
Volume318
DOIs
Publication statusPublished - 1 Feb 2023

Keywords

  • Arsenic reduction
  • Methane oxidation
  • Paddy
  • pH
  • pmoA

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