Two technicians calibrate data monitoring equipment at the Tangchang substation of Hohhot Environmental Monitoring Central Station, North China’s Inner Mongolia autonomous region, on May 8. The PM2.5 origin analysis work was carried out in some cities of Inner Mongolia, such as Hohhot and Baotou. By studying air samples to figure out the origins of PM2.5, the work seeks to provide reference and instructions for pollution control and treatment. Gradually the PM2.5 origin analysis will cover 12 cities and leagues in Inner Mongolia. [Photo by Liu Yide/Xinhua]

A technician of the Tangchang substation of the Hohhot Environmental Monitoring Central Station adjusts equipment for air sample collection on May 8. By analyzing the collected air samples, the technicians will try to figure out the origins of PM2.5. [Photo by Xinhua/Liu Yide]