Abstract:

Air pollution is a major environmental problem in cities. Much progress have been achieved in air monitoring and quality assessment at regional and national level based on emission inventories and measurements of ambient air concentrations taken by physical and chemical methods. The results of ambient air measurements make it possible to decide whether or not to limit the emission of certain pollutants. However, they do not permit direct conclusions on the effects of the measured pollutant concentrations on living organisms. The purpose of this study is to test the sensitivity of 30 2-3 year-old garden species transplanted into pots and exposed to differently polluted sites for 4 months during the growing season. Measurements on gas exchange parameters were made by using LCA-4 photosynthesis system. Based on these measurements, assessments of possible effects of air pollution on plants and their tolerance were also made. Monitoring data showed that the heavy traffic area received a much higher concentration of NOx than the industrial site, and both sites had high concentrations of SO2. The sites can be categorized from heavy to less pollution level in the order of heavy traffic area, industrial area, and relatively clean area by using an integrated pollution index. The Pn, E,gs differed among species and decreased for most species under polluted area. The Pn and E were closely linearly correlated with the gs under the relative clean site and polluted site，suggesting that most species had the ability to adapt to the pollution stress by adjusting stomatal operation. The evidence that the correlation of the Pn and E with g s had been weakened under the pollution stress also showed the unparallel nature and complexity in changes of Pn, E and gs. Based on the change in Pn, plants might be ranked as follows by their sensibility to air pollution： species that exhibited high sensitivity included Michelia maudiae, Allemanda schottii, Crateva trifoliate, Magnolia delavayi, Bischoffia jacanica, Lysidice rhodostegia, Michelia macclurei and Hibiscus rosa-sinensis. Species showing moderate sensitivity were Tristania confera, Bombax ceiba, Schefflera arboricola, Elaeocarpus hainanensis, Manglietia hainanensis, Elaeocarpus apiculatus, Swietenia mahagoni, Sterculia lanceolata, Fagraea ceilanica, Manifera persiciformis and Ficus macrocarpa, and those showing low sensitivity included Pittosporum tobira, Ficus altissima, Ficus microcarpa, Kigelia africana, Ficus benjamina, Mimusops elengi, Ormosia pinnata, Ficus elastica, Acmena accuminatissima, Nerium indicum and Ilex rotunda.