There are three main types of yellow snow not caused by urine-marking of animals. First, yellow snow can occur when the snow itself is full of pollen or pine. The golden appearance of the snow can be spread over a large area.
Second, yellow snow can be caused by air pollution. Certain pollutants in the air can give snow a yellowish tinge. Air pollutants will migrate towards the poles and become incorporated into the snow as a thin film. As sunlight hits the snow, a yellow hue can appear.
Snow can also fall from the sky with a yellow color. When snow contains particles of sand or other cloud seeds, the color can be yellow even as it falls through the sky. One example was in South Korea when snow fell in March of 2006 with a yellow tint. The cause of the yellow snow was an increased amount of sand in the snow from the deserts of Northern China. NASA's Aura satellite captured the event as weather officials warned the public of the hazards contained within the snow. Yellow dust storm warnings are popular in South Korea, but yellow snow is more rare.
Other yellow snows can fall as a result of industrial waste in the air. In March of 2009, an intense yellow snow fell on the Russian Urals region as a result of industrial pollution. The snow contained high concentrations of manganese, nickel and iron, chrome, zinc, copper, lead, and cadmium according to a Moscow News source.