Is the blackening of snow along busy streets caused by automobile exhaust fumes?

Not for the most part. It's mostly a mixture of snow, ice, road salt, dirt from cars/oil/tires/smoke/etc. I would assume that exhaust makes up a very small part of the dirt.
 

GoingUp

Lifer
Jul 31, 2002
16,720
1
71
Ive always wondered what the snow gets black from... It looks so nice when you drive through it the first time and then later its just a bunch of brown crap.

It would be interesting to have a couple of completely cleaned cars and drive them around in the same snow to see if it makes it black or not.
 

Looney

Lifer
Jun 13, 2000
21,938
5
0
It is from population. Dirt is brown, not black. There's a park there gets A LOT of activity even in the winter, and the trail gets all muddy up from the thousands and thousands of people that walk through it, but it looks nothing like the black crap that are on the roads. And it's not the salt or ashphalt of the road either, because this trail is partially paved, and salted.