Effects of ozone concentrations on biogenic volatile organic compounds emission in the Mediterranean region

Measurements of air volatile organic compounds (VOCs) and ozone concentrations in different rural sites of Catalonia (NE Spain) were conducted during 1995 and 1996, and the effects of ozone concentrations on biogenic emissions of Mediterranean plants were studied in open top chambers. A significant positive relationship was found between tropospheric ozone and VOC concentrations, which followed seasonal (maximum in early summer and minimum in early winter) and geographical (slightly larger concentrations in interior than in coastal sites) patterns. Results in the open top chambers fumigation experiments showed species-specific responses. There was no significant effect of ozone on VOCs and terpene emission by Aleppo pines, Pinus halepensis L., but there was an order of magnitude increase in VOC emission with increasing tropospheric ozone concentrations (plus 40 nl L-1) in tomatoes, Solanum lycopersicum L. var. Tiny Tim. This response of tomato plants thus opens the possibility of a positive feedback for tropospheric ozone formation.