In the reconstruction of the chemical evolution of mineral waters, sodium exchange for calcium and magnesium, upon contact
with soil and rocks, is often suggested. Such a process has been observed to take place on a large (and rapid) scale in NaCl
waste disposal: that infiltrated to the local groundwater at Lobatse, Botswana. The process was repeated in laboratory experiments.
Visiting Scientist at the Nuclear Physics Research Unit, University of the Witwatersrand, Johannesburg, South Africa, during
1972.