In a study in which a researcher from Ben Gurion University participated, geochemical evidence is presented for the involvement of iron oxides in the oxidation of methane by sulfate, and a mechanism for this involvement is proposed
Dr. Orit Sion from Ben-Gurion University of the Negev, in collaboration with her colleagues from the California Institute of Technology and the University of Cambridge, revealed new facts about the mechanism that prevents the release of large amounts of the greenhouse gas, methane, from the seabed into the air. The study was published by Orit Sion, in collaboration with Victoria Orfan and Jeff Merlo from Kataluk, and Gilad Antler and Sasha Turchin from the University of Cambridge, in the prestigious journal of the National Academy of Sciences, PNAS.
Methane is an important natural gas used for energy needs, but also an effective greenhouse gas that warms the earth. Therefore, it is very important to know the processes that produce methane and consume it.
About two thirds of the methane in the world is produced from anthropogenic sources (mainly industrial and agricultural activity) and about a third of it is produced from natural sources. Its main natural reservoir is in sediments on the ocean floor, but luckily for us about ninety percent of the methane produced in these sediments is microbially oxidized by sulfur (as sulfate) before it reaches the ocean water and the atmosphere. Despite the enormous importance of this process in preventing methane emissions into the atmosphere, its mechanism is still not well understood and is the subject of many studies.
In the study, geochemical evidence for the involvement of iron oxides in the oxidation of methane by sulfate is presented, and a mechanism for this involvement is proposed. The evidence is based on laboratory experiments done on sediments from methane seeps in the Pacific Ocean. The sediments were subjected to different conditions, including a significant addition of iron oxides and isotopically labeled methane (carbon 13), and the changes over time were examined. The experiments showed, through measurements of concentrations and stable isotopes of oxygen, sulfur and carbon, that the addition of the iron oxides led to the redox of the iron and a significant increase in the rate of methane oxidation by the sulfate.
