On soil activation by cosmic rays at different altitudes

TL;DR

This study investigates how cosmic rays at different altitudes may activate soil by transforming long-lived uranium and thorium nuclei into shorter-lived isotopes, potentially increasing radon production at higher elevations.

Contribution

It provides evidence linking cosmic ray flux to soil activation and radon increase, suggesting a new role of cosmic rays in soil radioactivity processes.

Findings

Radon concentration increases with altitude.

Cosmic rays may induce nuclear reactions in soil.

Higher cosmic ray flux correlates with increased radon production.

Abstract

Measuring radon-due neutron flux at various altitude (100, 1000, 1700, 4300 m above sea level) we found an evidence of significant increase of radon concentration with altitude. It was also conirmed by direct radon measurements at high altitude. This allowed us to assume cosmic rays could take part in process of soil activation: they transform long-lived nuclei of uranium and thorium to nuclei with shorter life-time through specific nuclear reactions. If the resulting nuclei belong to the U-238 radioactive chain they can lead to producion of Ra-226 and then to Rn-222, thus significantly increasing its production at high altitudes where cosmic ray flux is high.