Relationship between foliar chemical parameters measured in Melia Azedarach L. and environmental conditions in urban areas

A diagnostic study was done on Melia azedarach L. in relation to atmospheric pollutants in Córdoba city, Argentina. The study area receives regional pollutants, and it was categorized taking into account traffic level, industrial level, location of the sample point in relation to the corner, treeless condition, building type, topographic level and distance to the river. Water content and Specific Leaf Area (SLA) were calculated; and concentrations of soluble proteins, sulphur, hydroperoxy conjugated dienes (HPCD), chlorophylls (Total Chl) and pheophytins (Total Paeoph) were determined in leaf samples. HPCD correlated positively with industry, topographic level and distance to the river, and with a combination of the environmental variables (ECI); pigments correlated negatively with traffic level and with ECI; Total Phaeoph/Total Chl ratio correlated positively with traffic, building and ECI. On the basis of our results, traffic level, industrial level, building type, topographic level and distance to the river are the environmental variables to bear in mind when selecting analogous sampling points in a passive monitoring program. An approximation to predict tree injury may be obtained by measuring water content, soluble proteins, sulphur, HPCD and pigments as they are responsible for the major variability of data. This study revealed that M. azedarach was sensitive to air pollutants from traffic and industry. Thus, in those sampling sites with the maximum score for traffic level, industrial level and ECI, the highest values of the parameters that indicate foliar damage together with the least pigment concentration were observed.