help my city

[Hong Wang]

Hi: 

I'm a student from Guangzhou (P.R.China). Last year, I went back to my hometown and found my beloved city was full of dust in air, some time people even feel hard to breath. The dust mainly come from the construction and the traffic. At the moment, cleaning the air by stopping the construction and restricting the traffic seem not possible because developping the economy is more important;  To build more green parks seems impossible either because the land there is too expensive. Therefore, I wonder if by building roof garden can reduce the pollution.
 Any comments and suggestion are welcome, especially the idea about what plant is effect to reduce the dust in air. Thanks in advance.

Wang Hong