URUMQI, Oct. 9 (Xinhua) -- Zhang Xin still remembers the complaints she saw on social media some years ago: "In winter, you can't see the sun clearly in the city of Urumqi," and "The snow is all black."
Zhang, who works in the ecology and environment bureau of Urumqi, capital of northwest China's Xinjiang Uygur Autonomous Region, used to participate in the air-pollution prevention and control work for a long tim
