PM 2.5
from: http://www.nasa.gov/topics/earth/features/health-sapping.html
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Global satellite-derived map of PM2.5 averaged over 2001-2006.
Credit: Dalhousie University, Aaron van Donkelaar
秋梦无痕
一场秋雨无梦痕，春夜清风冻煞人。冬来冷水寒似铁，夏至京北蟑满城。
一场秋雨无梦痕，春夜清风冻煞人。冬来冷水寒似铁，夏至京北蟑满城。
from: http://www.nasa.gov/topics/earth/features/health-sapping.html
> View larger
Global satellite-derived map of PM2.5 averaged over 2001-2006.
Credit: Dalhousie University, Aaron van Donkelaar