VERTICAL OZONE PROFILES IN A PINE FOREST

Vertical profiles of ozone concentration have been measured in a pine forest located in the Landes region, in south-west France. In the daytime, ozone concentrations are nearly constant between ground level and an altitude of 35 m, the higher level of measurement. At night, important vertical variations of ozone concentration are observed in relation with temperature profiles. Analysis of the ozone profiles shows that the main ozone sink is the soil. When the ozone concentration near ground level is around zero, the ozone profile changes slowly, even in the main vegetation layer between 15 and 25 m height. This means that the chemical destruction of ozone at night is weak in comparison with its dry deposition at ground level.