The recent Yokahama IPCC meeting painted a stark warning on the possible effects of gases such as methane which has a greenhouse effect 32 times that of carbon dioxide. Now a team of Swiss-German researchers have shown that humic substances act as fully regenerable electron acceptors which helps explain why large amount of methane are held in wetlands instead of being released to the atmosphere. However, there are worries that if this system is disrupted it may enter into a vicious cycle to release large amounts of methane back into the atmosphere.
Wetlands, such as peatlands, have a high content of organic-compound rich humic soils, which are formed during the breakdown of biological organisms such as plants. When water levels are high, these soils remain wet, and so are starved of oxygen, causing the organic compounds to accept electrons from respiring bacteria - rather like the charging of a giant battery. This prevents these electrons from being used by methane-forming bacteria, and so prevents these bacteria from releasing methane into the atmosphere.
The researchers now found that this giant electrical reaction can also go into reverse, like the charging and discharging of a giant battery. As water levels drop due to periodic variations in weather, then the humic soils will tend to release the electrons to oxygen forming harmless water. However, there is a danger is that climate change could lead to higher water levels, causing these soils remaining submerged for a greater period, and so and the discharging process disappears thus leading to more methane formation.
Potentially even worse, increasing global temperatures may cause permafrost to melt, leading to the soils being charged by microbial activity with electrons but not discharged. This could release vast quantities of methane from the wetlands. This in turn causes a greater greenhouse effect, and so on in a potentially vicious cycle.
One of the two lead
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European Association of Geochemistry