A MODEL FOR THE RELATIONSHIP BETWEEN GASEOUS AND AQUEOUS CONCENTRATIONS OF SULPHUR DIOXIDE IN LICHEN EXPOSURE STUDIES*

Summary The linear relationship, ppm SO 2 (wt/wt, aqueous) = 10.3 , is evaluated experimentally for the gaseous concentration range 0–5 ppm and is confirmed theoretically. It is suggested that this physicochemical equilibrium expression is applicable to lichen exposure studies because lichens are poikilohydrous plants.