Surface ozone mixing ratio increase with altitude in a transect in the Catalan Pyrenees

Tropospheric ozone mixing ratios and their phytotoxicity and NO2 mixing ratios were measured along an altitudinal gradient at the Meranges valley in the Catalan Pyrenees. Biweekly measurements using Radiello passive samplers were taken along a transect of seven stations ranging from 1040 to 2400 m ASL from May to December 2004. As well, at each station biweekly evaluations were made of the visual symptoms of ozone damage in Bel-W3 and Bel-B tobacco cultivars. Whereas ozone mixing ratios increased with altitude, NO2 mixing ratios decreased from the valley floor upwards. Ozone damage rates were found to vary with time and space depending on local environmental and meteorological conditions, although the highest ozone damage to foliage was found in the stations at greatest altitude, especially wherever altitudinal micrometeorological conditions enhanced plant sensitivity.