The effects of human activities on the Earth’s surface, such as greenhouse gas emissions and deforestation, are well documented. Recently, hydrological researchers from the University of Arizona investigated human impact on the Earth’s deep depths, which range from hundreds of meters to several kilometers below.

“We examined how the rate of liquid production from oil and gas compared to the natural background water circulation and showed how humans have had a huge impact on the circulation of liquids underground,” said Professor Jennifer McIntosh. University of Arizona Department of Hydrology and Atmospheric Sciences and senior author of the journal article Future of the World, where the results are explained in detail.

“The deep underground is out of sight and out of sight for most people, and we felt it was important to provide context for this proposed activity, especially when it comes to our environmental impact,” said Grant Ferguson, lead author and research assistant on the study. professor. He is a professor in the Department of Hydrology and Atmospheric Sciences at the University of Arizona and a professor in the School of Environment and Sustainability at the University of Saskatchewan.

Future predictions and collaborative research

According to the research, these human-caused fluid flows will increase in the future due to strategies proposed as solutions to combat climate change. Such strategies include: geological carbon sequestration, which refers to the capture and storage of atmospheric carbon dioxide in porous rocks underground; geothermal energy production, which involves water circulating through hot rocks to produce electricity; and mining lithium to power electric vehicles from mineral-rich underground brine. The study was conducted in collaboration with researchers from the University of Saskatchewan in Canada, Harvard University, Northwestern University, the Korean Institute for Earth Sciences and Mineral Resources, and Linnaeus University in Sweden.

“Responsible stewardship of soil is central to the hope for a green transition, a sustainable future, and keeping warming to below a few degrees,” said co-author Peter Reiners, professor in the Department of Earth Sciences at the University of Arizona. study.

Human activity and groundwater circulation

When producing oil and natural gas, there is always some water, usually salt water, coming from deep within the earth, McIntosh said. Groundwater is often millions of years old and acquires salinity either through the evaporation of ancient seawater or by reacting with rocks and minerals. For more efficient oil recovery, more water is added to the brine from near-surface sources to compensate for the amount of oil extracted and maintain formation pressure. The mixed brine is then pumped back underground. This becomes a cycle of extracting fluid and reinjecting it deep into the soil.

The same process occurs in lithium mining, geothermal energy production, and geological carbon sequestration; All of these operations involve reinjecting brine from underground.

“We show that the liquid injection rate, or recharge rate, resulting from this oil and gas activity is higher than what occurs naturally,” McIntosh said.

Using existing data from a variety of sources, including measurements of fluid movements associated with oil and gas production and water injection for geothermal energy, the team found that current rates of fluid movement caused by human activity are higher compared to how fluids moved before the move. interfere with the person

As human activities such as carbon capture and sequestration and lithium mining increase, researchers are also envisioning how these activities may be recorded in the geological record, the history recorded in the rocks that make up the Earth’s crust.

Impact on microbial life and needs for future research

According to McIntosh, human activities could potentially alter not only deep underground fluids but also the microbes that live there. As fluids move, the microbial environment can be altered by changes in water chemistry or by the transfer of new microbial communities from the Earth’s surface to the subsurface.

For example, with hydraulic fracturing, a technique used to break up underground rocks with pressurized fluids to extract oil and gas, a deep rock formation that was previously free of appreciable microbes can cause a sudden burst of microbial activity.

McIntosh said much is unknown about the Earth’s deep interior and how it is affected by human activities, and it is important to continue working on these questions.

“We need to use deep underground as part of the solution to the climate crisis,” McIntosh said. “But we know more about the surface of Mars than we do about the water, rocks, and life beneath our feet.”