Ground-level ozone distribution pattern in summer of beijing and its foliar injury effect upon plants

Abstract

The ozone in the stratosphere protects the earth from harm due to ultraviolet radiation, while the ozone in the troposphere might do harm to human beings. Ozone below certain concentration can sterilize the air and do good to organisms, but high ozone concentration does harm to terrestrial ecosystems. Very high ozone concentrations were firstly found as pollutant in the smog of Los Angeles and its toxic effect upon plants received more attention. The rapid urbanization in China has caused the emission of large amounts of NOx and VOCs (the main precursors to O3 formation). Ambient ozone concentration has been the most serious air pollution among many cities in China. In this study, our objectives are: to discern the distribution pattern of ground-level ozone in Beijing; to find whether plants were injured by ambient ozone in Beijing; and to detect the distribution pattern of the damaged plants in this region. We used passive sampler to monitor ozone concentrations at 10 sites in the city and suburb of Beijing from July 1st to August 30 in 2012 and surveyed the foliar ozone symptoms on the basis of the Forest Health Expert Advisory System from August 15 to 19. The results indicated that the ozone concentrations in mountain regions were significantly higher than those in plain regions around Beijing. In the plain region, the ozone concentration in the green belt adjacent to main motorways was lower than that in parks. The mean ozone concentrations in the mountain, the park and the green belt near to main motorway were: 105.39 µg/ m3,68.49 µg/ m3 and 56.54 µg/ m3. Except for the green belt of motorway, 18 species showed typical ozone symptoms both in mountain and in plain regions. These plants are: Parthenocissus quinquefolia, Juglans regia, Ailanthus altissima, Pharbitis purpurea, Morus alba, Ulmus pumila, Sophora japonica, Sophora japonica f. flavi-rameus, Hibiscus syriacus, Kerria japonica, Hyptis suaveolens, Cassia tora, Populus tomentosa, Salix caprea, Sanguisorba sitchensis, Rhus typhina, Glycine max, Helianthus annuus. Ailanthus altissima was native and popular in mountain and plain around Beijing and its ozone symptoms was easy to diagnose. Therefore, Ailanthus altissima might work as bio-indicator of ozone in Beijing.