[seanmcdirmid]

Trees can help with carbon, but we are talking about small particles here. I guess they could trap them or something, but not on the scale of a typical polluted day in say Beijing. Anyways, in northern china, this wouldn’t be very workable as the pollution season corresponds to leafless tree season (and the trees turn a dreary brownish grey due to dust).

[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.