A foreign tourist wearing a protective mask takes a photo at Jingshan Park in central Beijing on Thursday, as a sandstorm swept over much of North China, turning the sky yellow and obscuring visibility. Most monitoring stations in the capital showed PM10 readings of more than 1,000 micrograms per cubic meter and PM2.5 readings of over 400 micrograms per cubic meter as of Thursday noon, according to data from Beijing Municipal Environmental Monitoring Center. Sandstorms were also reported in Hebei Province and are expected to clear Friday. Xinhua