Orange snow in Russia?

Dear Tom,
I heard that they recently had orange snow in Russia. What caused that?
— Charles B., Chicago
Dear Charles,
Orange-tinted snow covered areas near Sochi, Russia, back in March, a result of air-borne dust particles emanating from a Saharan dust storm. In the 1950s, the Chicago area was blanketed by an eerie, reddish-brown snow as strong southwest winds picked up topsoil from the Plains and lifted it into the snow-producing clouds. Similar circumstances brought brownish-yellow tinged snow to the Chicago area in February 2007. Colored snow also can occur in mountainous or polar regions where algae grows on glacial snow giving it a red, orange, green or purple color. In any major city, snow quickly takes on a dirty gray appearance with in a day or two after falling, a result of urban pollution.
Why did Russia get orange snow?