Response of methane production via propionate oxidation to carboxylated multiwalled carbon nanotubes in paddy soil enrichments

Abstract

Carboxylated multiwalled carbon nanotubes (MWCNTs-COOH) have become a growing concern in terms of their fate and toxicity in aqueous environments. Methane (CH4) is a major product of organic matter degradation in waterlogged environments. In this study, we determined the effect of MWCNTs-COOH on the production of CH4 from propionate oxidation in paddy soil enrichments. The results showed that the methanogenesis from propionate degradation was accelerated in the presence of MWCNTs-COOH. In addition, the rates of CH4 production and propionate degradation increased with increasing concentrations of MWCNTs-COOH. Scanning electron microscopy (SEM) observations showed that the cells were intact and maintained their structure in the presence of MWCNTs-COOH. In addition, SEM and fluorescence in situ hybridization (FISH) images revealed that the cells were in direct contact with the MWCNTs and formed cell-MWCNTs aggregates that contained both bacteria and archaea. On the other hand, nontoxic magnetite nanoparticles (Fe3O4) had similar effects on the CH4 production and cell integrity as the MWCNTs-COOH. Compared with no nanomaterial addition, the relative abundances of Geobacter and Methanosarcina species increased in the presence of MWCNTs-COOH. This study suggests that MWCNTs-COOH exerted positive rather than cytotoxic effects on the syntrophic oxidation of propionate in paddy soil enrichments and affected the bacterial and archaeal community structure at the test concentrations. These findings provide novel insight into the consequences of nanomaterial release into anoxic natural environments.

Peer Review #1 of "Greenhouse gas emissions from riparian zone cropland in a tributary bay of the Three Gorges Reservoir, China (v0.1)"

“…Mean CH 4 fluxes of the riparian zone from 2015 to 2016 in this study (0.47±1.53 mg•m -2 •h -1 ) were similar to values reported for other wetland catchments(0.0~2.22 mg•m -2 •h -1 ) (Badiou et al, 2011;Finocchiaro et al, 2014;Yang M et al, 2014).The production of CH 4 in various eco-systems is closely related to the anaerobic environment, which is beneficial to the methanogen metabolic activities Zhang et al, 2018). Soil water content, which affects the methane consuming capacity of methane-oxidizing bacteria by changing the transmission rate and the soil environmental condition (Koh et al, 2009), probably was a reason of the significant difference in the CH fluxes among the paddy fields, dry lands and grasslands.…”

A new insight into the strategy for methane production affected by conductive carbon cloth in wetland soil: Beneficial to acetoclastic methanogenesis instead of CO2 reduction

“…This research into the impact of carbon cloth on soil methane production is novel. Methanogenesis has been found to be stimulated by other conductive magnetite and carbon nanotube material (Kato et al, 2012;Yang et al, 2016;Zhang and Lu, 2016;Zhang et al, 2018;Zhuang et al, 2015). The promotion of CO 2 reduction by increased electron transfer is the key mechanism advocated by those studies.…”

“…Based on this, compared with artificial anaerobic fermentation system, strategies pertinent to use of conductive carbon materials in microbial methane production require clarification in a natural environment. Some studies showed that methanogenic process was also facilitated by electric syntrophy via magnetite (Kato et al, 2012;Xiao et al, 2018;Zhuang et al, 2015), biochar (Wang et al, 2017), and carbon nanotubes (Zhang and Lu, 2016;Zhang et al, 2018) in natural soil or sediments: however, little is known about the stimulation strategy of carbon cloth on methane production in natural environments.…”

Greenhouse gas emissions from riparian zone cropland in a tributary bay of the Three Gorges Reservoir, China

“…Mean CH 4 fluxes of the riparian zone from 2015 to 2016 in this study (0.47 ± 1.53 mg m −2 h −1 ) were similar to values reported for other wetland catchments (0.0∼2.22 mg m −2 h −1 ) (Badiou et al, 2011;Finocchiaro, Tangen & Gleason, 2014;Yang et al, 2014). The production of CH 4 in various eco-systems is closely related to the anaerobic environment, which is beneficial to the methanogen metabolic activities (Zhou et al, 2014;Zhang et al, 2018). Soil water content, which affects the methane consuming capacity of methaneoxidizing bacteria by changing the transmission rate and the soil environmental condition (Koh, Ochs & Yu, 2009), probably was a reason of the significant difference in the CH 4 fluxes among the paddy fields, dry lands and grasslands.…”