Beneath the ground, a hidden electrical world powers the chemistry that shapes ecosystems, controls water quality, and determines the fate of pollutants.
A new review published in Environmental and Biogeochemical Processes reveals that electrons—tiny charged particles essential to chemical reactions—can travel through soils and sediments much farther than scientists once believed.
These underground “electron highways” may open new possibilities for cleaning up contaminated environments.
Many natural processes depend on redox reactions, in which electrons are exchanged between different chemical compounds.
These reactions regulate nutrient cycles, influence how contaminants move through the environment, and provide microbes with energy.
For decades, researchers assumed that such reactions only happened on very small scales, limited to tiny “hotspots” on mineral surfaces or within microbial cells.
But new discoveries are overturning this view. According to a team from the China University of Geosciences, electron transfer in the subsurface can extend across surprisingly large distances, sometimes centimeters or even meters.
That means chemical processes that occur in one location can directly influence reactions far away, linking distant zones into vast underground networks.
On the smallest scale, electrons are exchanged at the interfaces between minerals, water, and microbes. But conductive minerals, natural organic molecules, and special microorganisms known as “cable bacteria” can serve as electron bridges.
These create longer pathways, allowing charges to move through soils over centimeters.
In some cases, step-by-step connections form chains of transfer that stretch tens of centimeters, effectively building underground circuits.
“These findings challenge the old view that electron transfer is strictly local,” said lead author Professor Songhu Yuan.
“We now know that redox processes can connect across surprisingly large distances, coupling reactions in one zone with those in another. This has profound implications for contaminant remediation and environmental sustainability.”
One exciting possibility is “remote remediation,” where pollutants deep underground are broken down without the need to inject chemicals directly.
Conductive minerals or added materials like biochar can expand microbial activity, while cable bacteria can connect oxygen near the surface to sulfides buried deeper down, reducing harmful emissions.
The review also outlines key goals for future research, including developing better tools to measure electron flows across different scales and designing new environmental technologies that take advantage of these hidden networks.
“Our work provides a conceptual framework for thinking about the subsurface as an interconnected redox system,” said co-author Dr. Yanting Zhang.
“By understanding how electrons move underground, we can better predict the fate of nutrients and pollutants and design more effective strategies to protect groundwater and ecosystems.”
By mapping these underground electron highways, scientists may one day be able to plug into Earth’s natural electrical grid, offering new ways to restore contaminated soils and aquifers while working in harmony with the planet’s own chemistry.
