Study Uncovers Hydroxyl Radical's Role for Greenhouse Gas Production During Soil Drying–Rewetting

A new study, led by Prof. ZHANG Yuanming from the Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, has unveiled a previously underestimated factor in greenhouse gas emissions from arid environments: hydroxyl radicals, often dubbed "free radicals".

The study reveals that these highly reactive molecules are unexpectedly produced when desert soils get wet again after a period of dryness, significantly influencing the release of carbon dioxide (CO₂) and nitrous oxide (N₂O). The study was recently published in Global Change Biology.

To understand this phenomenon, the research team collected surface soil samples in the vast Gurbantunggut Desert. Back in the laboratory, they simulated the crucial process of soil rewetting, mirroring real-world rainfall events. Alongside experiments specifically designed to control and neutralize hydroxyl radicals, they measured changes in cumulative greenhouse gas emissions, enzyme activity, and the composition of organic matter.

By examining the samples, the researchers aimed to pinpoint the exact sources of hydroxyl radical production and decipher the mechanisms by which these radicals, through abiotic oxidation, directly impact the emission of CO₂ and N₂O, especially during sporadic summer rainfall.

Researchers found that rapid microbial activation following soil rewetting is the primary pathway for hydroxyl radical production. During microbial metabolism, NADPH oxidase family enzymes catalyze oxygen molecules in the environment, leading to the generation of large quantities of hydroxyl radicals.

They further confirmed that hydroxyl radical oxidation synergizes with microbial enzymatic reactions during soil rewetting to promote CO₂ release and facilitates the transformation of NH₄^⁺ to NO₃⁻, thereby dominating N₂O emissions.

"While the direct impact of these radicals on CO₂ emissions was found to be moderate, their role in driving N₂O emissions proved to be far more pronounced and decisive," said GUO Xing, first author of the study.

This study highlights the critical role of hydroxyl radical in biogeochemical cycles and its previously overlooked influence on major greenhouse gas emissions.

Read the full article: https://doi.org/10.1111/gcb.70552

Contact

LONG Huaping

Xinjiang Institute of Ecology and Geography

E-mail: longhp@ms.xjb.ac.cn

Web: http://english.egi.cas.cn