Reference News Network, November 13 report. According to the U.S. "Newsweek" website on November 11, Pennsylvania is home to tens of thousands of abandoned oil and gas wells, some of which may release harmful chemicals into the atmosphere and groundwater.

This is a warning from a study led by a geochemist from Pennsylvania State University. They investigated 18 abandoned wells in the Allegheny National Forest and nearby areas, finding that these wells were not sealed, directly exposed to the air, eroded and damaged, and causing environmental harm.

"We found that abandoned oil and gas wells are leaking methane into groundwater, causing dangerous changes in water quality," said Samuel Shahin, a researcher from the University of Minnesota, who told "Newsweek" reporters. He completed his Ph.D. in Earth Sciences at Pennsylvania State University.

Researchers also found high concentrations of dissolved iron and arsenic in some locations' groundwater. Methane is a powerful greenhouse gas that absorbs more heat than carbon dioxide. It interacts with rocks near the wellhead, releasing metals into the groundwater.

The findings of this study indicate a larger problem across the United States.

Shahin explained: "These wells are considered abandoned or isolated (we even don't know who drilled them initially). Many of these wells were drilled over 100 years ago, and the regulations regarding how to handle oil and gas wells after they were decommissioned were very loose at that time."

He said: "They usually just plugged these wells with tree stumps or stones, while modern oil well plugging operations use concrete. Most of these oil and gas wells were built in an era when groundwater protection was not highly prioritized. Therefore, compared to modern oil and gas well construction, there were fewer measures in place to prevent leaks after these wells were decommissioned."

The research team visited each oil and gas well between one to seven times and collected and analyzed 36 water samples from around and near the wells, streams, and groundwater aquifers.

They found that some sampling sites had large amounts of methanotrophic bacteria (microorganisms that consume methane), while others had large amounts of methanogenic bacteria (which produce methane).

In locations where methanotrophic bacteria were more abundant, the levels of dissolved metals in the groundwater were also higher. The research group stated that one-sixth of the samples exceeded the U.S. Environmental Protection Agency's limit for arsenic in drinking water, and more than half of the samples exceeded the EPA's limit for iron in drinking water.

The researchers said: "We already knew that these oil and gas wells might collapse on the surface, emit methane into the atmosphere, and contribute to climate change. What we show here is that the degradation of abandoned oil and gas wells underground may pose a threat to groundwater quality, especially when methane leaks into groundwater rather than the air."

"There are a lot of such abandoned oil and gas wells - Pennsylvania may have 300,000, and the entire U.S. may have 3 million, with countless worldwide. Not all oil and gas wells will leak, but their sheer number makes monitoring them difficult. For example, in Texas, these wells have started to become a real problem."

These abandoned oil and gas wells pose threats to the environment, animals, and human health. Shahin explained: "If people get their water from well water (which is common in rural areas near our study region), these leaking oil and gas wells may contaminate the quality of drinking water wells."

He said: "Methane is non-toxic, but if it accumulates in large quantities in groundwater, it is very flammable and can cause explosions. Our study results show that the main risk is arsenic pollution, which is caused by methane leaking from oil and gas wells interacting with rocks and microorganisms present in the aquifer. These oil and gas wells can also leak groundwater to the surface, polluting rivers."

The research team even found deer hoofprints in the soil near these wells, as they like to drink the salty water that leaks out. (Translated by Xu Yanhong)

Original article: https://www.toutiao.com/article/7572114266191331882/

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