杭州市6种常见绿化树种滞尘能力及光合特性

树种滞尘能力成为城市绿化树种选择的一个重要因素。为探究能够有效减少空气中的细颗粒物数量的城市树种类型，对杭州市6种典型阔叶乔木（广玉兰Magnolia grandiflora，樟树Cinnamomum camphora，珊瑚树Viburnum odoratissinum，苦槠Castanopsis sclerophylla，木荷Schima superba和黄山栾树Koelreuteria bipinnata）的夏季滞尘能力进行了研究。夏季雨后第5天和第10天，对叶片滞尘能力，林下空气中直径小于或等于2.5 μm的颗粒物（PM_2.5），空气中直径小于或等于10 μm的颗粒物（PM₁₀）及空气负离子浓度、叶片叶绿素荧光参数进行测定。结果显示:6种树种能够有效滞尘，且滞尘能力差异显著（P < 0.05），木荷和广玉兰滞尘能力最强，与其他树种间差异极显著（P < 0.01）；不同树种单位叶面积滞尘量随滞尘时间的增加而增加；雨后第5天和雨后第10天，樟树冠下PM_2.5和PM₁₀质量浓度最低，空气负离子浓度比较高，削减颗粒物（PM）能力高于其他树种；随滞尘时间增加，大部分树种叶片叶绿素相对含量、F_v/F_m和Y_ield呈现下降趋势，光合特性受到抑制。根据研究结果，具有高滞尘能力同时叶绿素荧光参数受影响小的树种，如广玉兰和樟树，可以作为城市绿化的优选树种。

Differences in dust removal capability and photosynthetic characteristics of six common tree species in Hangzhou City

Dust removal ability is an important factor in the choice of green tree species when environmental pollution of a city is becoming serious. To reduce particulate matter in the air, differences among six tree species commonly cultivated (Magnolia grandiflora, Cinnamomum camphora, Viburnum odoratissimum, Castanopsis sclerophylla, Schima superba, and Koelreuteria bipinnata) in Hangzhou City were studied. At the 5th day and 10th day after rain in summer, the dust capturing capacity of tree leaves was measured by immersion weighing method and chlorophyll-fluorescence indexes of tree leaves were mearsured using PAM-2100, as well as the concentration of particulate matter(PM_2.5, PM₁₀), and the air negative ions under these trees were surveyed by air quality minitoring instruments. Results showed that leaves of these six urban trees species captured dust from the air effectively with significant differences among the six tree species (P < 0.05). Leaves of S. superba and M. grandiflora compared to the other tree species absorbed dust most effectively with highly significant differences(P < 0.01). The amount of dust absorption per unit leaf area for the trees 10 days after rain was increased significantly(P < 0.01) than that of 5 days after rain. For most tree species, relative chlorophyll content, F_v/F_m (the ratio of variable fluorescence from dark-adapted material and maximum fluorescence signal from dark-adapted material), and yield showed a decrease with an increase of dust residence time on leaf surfaces. Thus, the photosynthetic characteristics of these six tree species were inhibited with PM stress. Almost all of the trees can reduce the particulate matter, and release the negative air irons. According our results, the trees with high dust removal capability and small effect on photosynthetic characteristics, such as Magnolia grandiflora and Cinnamomum camphora, can be selected as the preferred tree species for urban greening.