Dust Retention and Physiological Responses of Evergreen Tree Leaves in Zhengzhou city

  Objective   Dust retention of 7 typical species of evergreen trees in municipal Zhengzhou, Jiangsu was studied.

  Method  Deposit of dust falloff on leaves of the evergreen trees was collected by a 3-layer membrane filtration method. Physiological indicators and surface structure of the tree leaves in areas under varied degrees of atmospheric pollution were compared.

  Result   On a per unit leaf area basis, the dust retention of coniferous evergreens was significantly higher than that of broadleaf counterparts. Of the conifers, Sabina chinensis was higher in retaining dust than Cedrus deodara, while the broadleaf Ligustrum lucidum the highest and Nandina domestica the lowest. Most trees in severely polluted areas were relatively low on the contents of chlorophyll a and b but high on malondialdehyde, as the leaves tended to gather more dust. A significant correlation was also observed between the dust retention and physiological indicators of the tree leaves. Dust particles largely collected in the grooves, midribs, and stomata on a plant, and the size and density of the stomata could be affected by the worsened air pollution and so the dust retention. A principal component analysis on the pollution resistance of the evergreens placed the species in a descending order of C. deodara, S. chinensis, L. lucidum, Photinia serratifolia, Buxus megistophylla, Pittosporum tobira, and N. domestica.

  Conclusion   For an ecological-friendly urban landscaping in Zhengzhou, it would be more desirable to choose C. deodara and S. chinensis than the others.