Soot is black and therefore it absorbs sunlight when it is in the air. It blackens the snow as it is deposited from the atmosphere into snow. Snow crystals in snow layers on the ground grow and absorb more sunlight, so the snow melts faster. The soot particles form clouds that reflect sunlight and capture the heat that radiates from the earth. These are all effects of soot in the air and in snow in the Arctic, which are elaborated in an article that you can read by clicking on the image:
