Is it normal for brake pads to emit an odor? Not a duplicate of this one I think, circumstances are different.

My bike has rim brakes. The last two day I have cycled on snowy ground, and at the end of the rides the brake pads where covered in dirty snow. 

Now I have noticed that when I use the rear brakes, I immediately smell a peculiar odor, even with light braking like the last 10 meters before a traffic light. The closest odor I can relate to it is the one of a used rifle shell few days after it was shot.

Is this normal?
Generally no - smell would be an indication of heat and vaporisation of something.  In a brake it would be the pad turning to smoke with overheating. 

If your pad is that hot then your rims are about as hot, and will be very noticeable to the touch.  This level of heating normally requires hundreds of metres of fast descent, combined with hard braking.

Snow on the brakes would pretty much make overheating impossible.

I suspect the snow has an odour.  Its also possible your location salts the roads in times of snow, and this may be close enough to trigger your nose-memory.