We can classify them -- harmless steam plumes, white and evanescent;polluting smokestacks, dark and persistent -- and provide policy makers with a map of neighborhood pollution.

我们可以对它们进行分类 - 无害的蒸汽羽流， 白色和转瞬即逝;污染烟囱，黑暗和持久 - 并为政策制定者提供邻里污染地图。