It is well known that human activities significantly affect the Earth, and most often in a negative way. And while the impact of human activities on the surface of the Earth has been well studied, we do not know exactly what is happening inside planet , underground. Or do we?
Hydrology researchers from the University of Arizona (they also collaborated with other universities) investigated how human activities affect the Earth, deep inside it, in a zone located hundreds of meters to several kilometers below the surface.
The researchers compared the production rates of fluids, such as oil, with the natural circulation of water and showed how humans affect the circulation of fluids underground.
According to one of the researchers, the subsurface is out of sight and that's why most people don't even think about it. However, there are environmental impacts there too.
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The study says that in the future, human-induced fluid flows are predicted to increase, with strategies proposed as solutions to climate change. Such strategies include: geological carbon sequestration, which traps and stores atmospheric carbon in underground porous rocks; geothermal energy generation, which involves circulating water through hot rocks to generate electricity; and many others.
“ Responsible management of the subsoil is central to any effort for a green transition, for a sustainable future and for keeping temperatures below certain degrees ,” said Peter Reiners, a professor in the UArizona Department of Geosciences and co-author of the study, regarding human activities in the subsoil
With oil and gas production, there is always some amount of water, usually saline, that comes from deep within the Earth. Groundwater is often millions of years old and gets its “saltiness” either from the evaporation of ancient seawater or from reaction with rocks and minerals. To more effectively recover oil, more water, from sources near the surface, is added to the saltwater to replenish the amount of oil that was removed and to maintain reservoir pressures. The mixed saline water is then injected back to the surface. Thus, we speak of a cycle of producing fluids and reinjecting them into the subsurface.
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The same process occurs in lithium mining, geothermal energy production, and geological carbon sequestration.
"We show that the fluid injection rates or recharge rates from these oil and gas activities are greater than what occurs naturally," said a researcher.
Using data from various sources, the research team found that current rates of fluid movement, caused by human activities, are higher compared to how fluids used to move naturally.
As human activities increase, the researchers predict how those activities could be recorded in the geological record, which is the history of the Earth as recorded in the rocks that make up crust . They conclude that human activities affect not only deep underground fluids, but also the microbes that live there. As the fluids circulate, microbial environments can be altered by changes in water chemistry or through the introduction of new microbes from the surface .
Researchers say there are still many things we don't know about the impact of human activities on the Earth's subsurface, but it's important to learn them.
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Human activities can lead to significant changes in the geological structure and composition of rocks. This can have an impact on soil stability and cause geological phenomena. In addition, as we said, the distribution and movement of groundwater is affected. This can lead to changes in the quality and availability of water for human use, and can also affect wetlands.
Source: phys.org
