Finland borehole reveals new secrets « Euro Weekly News

A recent study found volatile organic compounds (VOCs) 2.3 kilometres below ground in Finland.

These compounds, which are usually linked to poor indoor air quality and industrial pollution, were discovered in the Outokumpu borehole drilled by the Geological Survey of Finland for research purposes between 2004 and 2005.

Investigators from Helsinki University and Finland’s VTT Technical Research centre nevertheless explained that VOCs also occur naturally in wetlands, forests, volcanoes and hydrothermal vents, the openings on the seabed that flow with heated, mineral-rich water.

The Outokumpu VOCs were discovered at depths that ranged from 500 to 2,300 metres, the first time that these compounds had been found in crystalline bedrock and uncontaminated groundwater.

The findings, which were published in the Communication Earth and Environment journal in January, are expected to provide better understanding of the global carbon cycle, together with the quality of the air in mines and other underground facilities.

Different smells of bedrock groundwater

The joint study also revealed the important role of microbes in the deep biosphere – the ecosystem of organisms and their living space beneath the earth’s surface – in breaking down VOCs.

“We were guided by smell,” assistant professor Riikka Kietavainen from the University of Helsinki, who oversaw the geochemical section of the study.

“The smell of the bedrock groundwater in the Outokumpu drill hole was described as resembling the ocean or the sewer, even slightly sweet,” the professor added, since different people differed in their identification of the smell.

“Research at the borehole will continue,” Kietavainen said.

Outokumpu borehole financed by Russia

The Outokumpu borehole, which is located in the western section of North Karelia in an area known for its iron deposits, is 2.5 kilometres deep and 22 centimetres wide, with a temperature of more than 40 degrees at its base.

Drilled through crystalline bedrock dating back 1.9 billion years, it encountered groundwater that was tens of millions of years old and had a salt content of up to 70 grammes per litre, twice as much as seawater.

The  €7 million cost of sinking the borehole was paid by Russia, which also carried out the drilling work as part of the Soviet Union’s national €600 million trading debt to Finland after the USSR ceased to exist in 1992. Some of this was paid in cash and some in goods and services contracts.