关键词: 有序加权平均, 城市增长边界, 生态适宜性, 情景分析, 雨洪淹没

Abstract: Lead (Pb) pollution caused by PM_2.5 is becoming increasingly serious. In this study, PM_2.5 particles were generated by aerosol generator to simulate different Pb pollution levels. The adhesion, absorption and transportation of PM_2.5Pb by leaves of Populus euramericana ‘Neva’ seedlings were studied. The changes of stomata and physiological characteristics in P. euramericana leaves were also investigated. The results showed that Pbcontaining particles can be adhered by the leaves, and the number of Pbcontaining particles on leaves was higher under the severe than the low pollution treatment. The content of Pb was the highest in leaves, while lower in stems and roots under both the low and severe pollution treatments. However, there were some differences in the transportations of Pb from leaves to stems and roots between the two treatments. In the low pollution treatment, Pb was transported from leaves to stems and roots 3 and 7 days after the treatment, respectively. By contrast, Pb in leaves was transported to roots only 3 days after the severe pollution treatment. Ultramicroscopic observation indicated that Pbcontaining particles first appeared in the cell wall of leaf epidermal cells, and was then transported to mesophyll cells through apoplast. In the mesophyll cells, Pbcontaining particles were mainly distributed in cell wall and cytoplasm, with a few particles observed in vacuole. The stomatal aperture, MDA and proline content, and SOD activity in P. euramericana leaves exhibited adaptive changes with the extension of time under both low and severe Pb pollution treatments. Our results demonstrate that Pb in PM_2.5 particles could be adhered and absorbed by the leaves of P. euramericana, and P. euramericana can adapt to Pb pollution through decreasing stomatal aperture, osmotic adjustment and increasing oxidation resistance.

Key words: rain flooding, ecological suitability, ordered weighted averaging, urban growth boundary, scenario analysis.