Modern pollutants can reach deep fossil aquifers

Contemporary pollutants can reach deep wells that tap fossil aquifers, says a study by an international team of researchers.

Aquifer. Image credit: Hans Hillewaert/Wikipedia (CC BY-SA 3.0)

More than half of some 6,000 wells studied around the world by the researchers showed traces of tritium, a radioactive isotope of hydrogen that has been marking water since 1953 when nuclear weapons testing became widespread. As tritium released by nuclear tests shows up in rainfall, it has become a handy tool in studying hydrological cycle.

The discovery of tritium traces in deep fossil aquifers, which were originally recharged by precipitation more than 12,000 years ago, is being attributed by the researchers to contamination by ‘younger’ groundwater closer to the earth’s surface.

Though fossil waters—common in wells deeper than 250 metres—are found in major aquifers, their global extent and depth are not clearly understood.

Currently, humans use groundwater for agriculture, but we don't know how much of it is fossil groundwater. Fossil groundwater is non-renewable and won't be recharged in human time scales

The researchers estimate that more than half of the total groundwater in the uppermost one kilometre of the Earth’s crust is fossil groundwater. Their analysis suggests that these waters are more vulnerable to modern contamination than previously thought.

human activity can pollute groundwater particularly in the shallowest few hundred metres where it is relied upon for water supply and irrigation. (SciDev.Net)

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