Repercussions of a drop in the atmospheric fluorine pollution on the vegetation of an alpine valley

Following the shut-down of a workshop responsible for fluorine pollution of the air in an Alpine Valley it was shown how the vegetation responds to such depollution. The results obtained on samples taken from resinous trees before and after the shut-down revealed that a factor 3 reduction in the fluorine content of the air led to a drop of a similar order of magnitude in the pollution level of the vegetation. The samples taken beforehand were analyzed for fluorine by 14MeV neutron activation according to a non-destructive method particularly well suited to measurements on distinctly polluted samples. Those taken after the shut-down were analyzed by means of an electrode specific to fluorine. This method is much more sensitive than the former and had to be used because of the very sharp drop in the fluorine pollution