The presence of ferrihydrite enhances greenhouse gas-methane emission in the environment.

Aquatic system is the major source of atmospheric methane. This study explored the influences of ferrihydrite, which is widely existed in natural aquatic system, on methane emission. Results showed that the presence of ferrihydrite led to 26.4% more methane emission. By tracking the transformation of organic compounds, it is revealed that the enhanced methane emission was attributed to greater hydrolysis and degradation of refractory compounds. More specifically, the remaining humic-like substances (HS) in ferrihydrite group (46.4 mg/L-C) were only half of that in control group (80.1 g/L-C) after 30-day incubation. The X-ray photoelectron spectroscopy spectrum confirmed the more active oxidation of organics occurred in ferrihydrite group. It was also found that ferrihydrite aided in sustaining microbial activity at stationary and starvation phases. Further study on microbial communities found that ferrihydrite promoted the enrichment of both functional and electroactive genera. This study provides insights into the greenhouse gas emission in natural environment. Unlabelled Image • Ferrihydrite enhanced methane emission by 26.4%. • Ferrihydrite facilitated the biodegradation of recalcitrant compounds, such as HS. • XPS spectrum evidenced dehydrogenation oxidation process under anaerobic condition. • Ferrihydrite aided in sustaining microbial activity during substrate limited phases. • Functional and electroactive genera were enriched with the presence of ferrihydrite. [ABSTRACT FROM AUTHOR]