Lanzhou City, the main transport junction in northwestern
China, contains many factories including those used for
petroleum processing, chemical combination and machine
assembly. The Lanzhou Valley is located in northern China
at the junction of the Tibetan Plateau, the Alxa Plateau and
the Loess Plateau. The distinctive trough-shaped topography,
its persistent stable boundary layer, and the large
amount of emissions originating from coal-fired factories
and vehicle emissions, have led to Lanzhou’s poor air and
soil quality.