https://www.peren-revues.fr/pollutionatmospherique/3759 Entrées d’index fr 0 https://www.peren-revues.fr/pollutionatmospherique/3754 L'évaluation des risques pour la santé et l'environnement liés à différents types d'exposition tels que la pollution de l'air, nécessite d'élargir les activités de surveillance de l'environnement. En milieu urbain, le trafic automobile devient la principale source d'émission de polluants entraînant dans les périodes de fort ensoleillement l'élévation des niveaux l'ozone qui peuvent quelquefois dépasser les valeurs réglementaires. Il est donc important de connaître sa distribution au niveau d'une agglomération. L'utilisation d'un bioindicateur végétal, le tabac Bel-W3, particulièrement sensible à l'ozone, a permis d'étudier et de réaliser la cartographie des différents niveaux d'ozone en juin, juillet et août 1996 sur la Communauté Urbaine du Grand Nancy. En juin, période caractéristique d'ensoleillement prolongé accompagnée d'un trafic urbain dense, l'étude cartographique montre une répartition concentrique autour du noyau urbain. La présence d'ozone la plus élevée se rencontre à la périphérie de l'agglomération, particulièrement au nord-est de Nancy-ville, où le panache de pollution de la ville se déplace sous l'influence des vents dominants, et à l'ouest où le relief accentué favorise l'accumulation de polluants. In urban areas, gaseous and particular vehicle emissions during periods of high traffic activity can react under the influence of sunlight to create a variety of products including ozone. Ambient ozone concentration can be relatively high and recommended levels can be reached during a peak period in the suburbs. Therefore, the elevated concentrations of nitrogen oxide NO in the vicinity of motorways with heavy traffic, in combination with the fast chemical reaction between this chemical species and ozone, causes a local depression in the ozone concentration. Due to its large geographical diffusion, ozone represents a problem on a regional scale and is becoming an important component of photochemical air pollution. The local effect on the air chemistry is important from a phototoxic point of view and should be possible to detect by the use of an ozone indicator plant. Sensitive higher plants may be used as indicators of air pollutants effects for studying the occurrence and distribution of air pollutants and their consequences in place and time. The intensity of visible foliar injury evaluated in terms of the percentage of leaf area covered by necrotic lesions, was shown to be mainly related with integrated ozone exposure.We report here results of a urban survey (Communauté Urbaine du Grand Nancy) of ozone concentrations, using the appearence of visible injury of the leaves of a sensitive plant species Nicotiana tabacum cv. Bel-W3, as an indicator of the presence of the pollutant. During the summer months studied, ambient ozone levels exhibited substantial spatial and temporal variations. In June, the meteorological conditions were favourable for the photochemical formation of ozone. The amount of leaf injury in the central urban area was relatively low, white it was higher at the periphery such as Nord-East Nancy, with respect to wind direction sectors, and was tern areas suggesting an altitudinal influence. The percentage of ozone-injured leaves shows a clear trend with the lowest values close to the motorways and in central Nancy compared to residential suburban areas. These effect reflect local NOX emissions and is explained by the reaction between NO and O3 causing a local depression in O3 concentration in the vicinity of the motorways and activity zones. The overall results suggest that the visible foliar responses of tobacco Bel-W3 can be used as a qualitative, but not necessarily as a quantitative indicator of relative ambiant O3 urban air pollution on a generalized temporal or spatial scale. ven., 21 mars 2014 13:45:24 +0100 mar., 05 juil. 2016 11:36:10 +0200 https://www.peren-revues.fr/pollutionatmospherique/3754