But one thing is very different: He's become a celebrity² in cyberspace³ almost overnight, after his pictures, which depict⁴ what the rampant⁵（蔓延的） smog in Beijing looks like under his microscope, spread like a virus on China's major micro-blogging site Sina Weibo, since he posted them last Friday. Now the media is hounding him for interviews.

 

"Why do I become famous when I took pictures of the smog?" he asks with a wry⁶ smile. "I have taken numerous pictures of beautiful nature whenever I have spare time, but there are no more than 10 interview requests for me every year before. Now, I have to answer dozens of phone calls from media every day.

 

"But I only gained 2,000 more followers⁷ over the weekend. I guess the micro blog is not as popular as before," he says, jokingly.

 

On Monday morning, a camera crew from a TV station based in southern Hunan province even took a flight to Beijing just to record how Zhang takes pictures of the Beijing's most-talked about feature: the floating enemies in the air.

 

The process is not complicated: He puts microscope slides on his windowsill（窗台） and collects the samples covered by fallen dust after 10 hours.

 

Zhang's apartment is on the eighth floor, which he says is perfect for capturing the densest⁸ levels of smog.

 

As a Beijing native, Zhang explains his original purpose is to "deconstruct" Beijing's smog and unveil its shroud⁹ of mystery.

 

"People have higher and higher standards for the environment," he says. "When I was a child, I was annoyed by the frequent sandstorms, so I feel Beijing's air seems much better now all in all because there are hardly any sandstorms in recent years. Now, we've noticed PM2.5, which has long been neglected."

 

Although he graduated as a science major from Beijing Normal University, Zhang says it is difficult for him to give an exact definition of what smog is in Beijing. "It's too complicated, and its ingredients keep changing."

 

Under his scope, which magnifies the sample 1,000 times, the smog is found to contain minerals, fragments of animal fur and insects, seeds and burnt dust. But many are compounds, he says, which are more difficult to identify.

 

"I wanted to know if there are many pollen¹⁰ grains in the early spring's smog, and my guess turns out to be right," Zhang says, noting there are on average 10 pollen grains found on each slide.

 

"Though the number is low compared with other ingredients of smog, it may partially¹¹ explain why smog makes us feel uncomfortable because many people are allergic¹² to pollen."

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