A worker discharge sewage from a train at the Golmud Station of the Qinghai-Tibet railway in Golmud, northwest China's Qinghai Province, May 26, 2016. The 1,956-kilometer-long Qinghai-Tibet railway, the world's highest altitude train line, has been put into service for 10 years. It links Lhasa, capital of southwest China's Tibet Autonomous Region, and Xining, capital of Qinghai Province in northwest China. [Photo: Xinhua]