[darethas]

Correct my understanding here where I am wrong - In my mind, if a leaf of a tree or any vegetation photosynthesizes, it is pulling in air (dirty air by your account which is why those leaves are brown) By the very virtue of that fact, it would be pulling in those small particles as well. The paper I referenced states that this happens to an extent, which is why trees during the leafy season are more effective at reducing PM2.5 than when they are bare.

[seanmcdirmid]

You are probably right, but a better solution would be to create breeze ways that would allow wind to blow out the pollution more easily. These could be coupled with forests, of course. These cities have plenty of trees, but they aren’t newrly enough and anyways winter is the worst season.