The grid of all BTV building photos by Beijinger Zou Yi in 2014 creates a clear picture of Beijing's fluctuating pollution levels. [Photo by Zou Hong/China Daily]

A photographer focuses on Beijing's pollution to create a clear picture of the capital's murky air quality. Lin Qi reports.

Beijinger Zou Yi's morning routine includes snapping a daily photo of the Beijing Television station 150 meters outside his apartment window and tweeting the image to his Sina Weibo microblog.

He also posts a 3x3 grid juxtaposing the photo with those of the past eight days of the same building from the same angle. These reveal the fluctuating pollution levels, as some photos show skies that are cobalt blue and others that are leaden.

Zou has also tweeted shots of the China World Trade Center Tower III－the capital's tallest building－where he works. Viewers can get a better sense of air visibility since the tower is 800 meters away, he explains.

Zou usually tweets for his 1,200 followers between 6:30 am and 8:30 am, depending on when the sun rises as the seasons change.

He uses the tag "#yi mu liao ran#", which literally means, "apparent at a glance". Zou also posts on the instant-messaging platform WeChat.

"Only environmental issues capture everyone's attention these days," he says.