The numbers from the statistics bureau told Streets the total amount of mercury that might be emitted, but he also needed to know how much actually made it into the air. To obtain that information, he turned to pollution detectives—a group of professional contacts he had met at conferences, along with graduate students who spent time in his lab. Most of the time, Chinese factories turned these “spies” away. “Factory owners had nothing to gain and a lot to lose,” Streets says. “They were nervous that the results would get leaked to the government.”
Yet some of Streets’s moles got through by guaranteeing that the data would stay anonymous. Once inside, they took samples of raw materials—zinc ore in a smelting facility, for example—and installed chemical detectors in smokestacks. After a few days of data collection, they passed the information to Streets.
The statistics Streets collected were hardly airtight. Factory foremen and provincial officials were not above providing inflated data to make themselves look more productive, and the managers who were willing to let his inspectors take measurements were often the very ones with nothing to hide. “There’s still a lot of uncertainty,” Streets concedes, “but we know more than we did before.”
In 2005 Streets and his team reported their first tally of human-generated mercury emissions in China, for the year 1999. The scientists estimated the amount at 590 tons (the United States emitted 117 tons). Almost half resulted from the smelting of metals—especially zinc, because its ores contain a high concentration of mercury. Coal-burning power plants accounted for another 38 percent of Chinese mercury emissions, and that percentage may be going up. As recently as 2007, China was building two new power plants a week, according to John Ashton, a climate official in the United Kingdom.
Streets’s team published a subsequent inventory estimating that China’s mercury emissions had jumped to 767 tons in 2003. “Mercury emissions in China have grown at about 5 to 6 percent a year,” he says. “It’s pretty much undeniable.”
Streets had shown that China was churning out mercury, but he was left with a big uncertainty: What happened to it on its journey aloft? Finding the answer fell to Hans Friedli, a chemist at the National Center for Atmospheric Research (NCAR) who had spent 33 years working for Dow Chemical. Friedli had found his own path into the esoteric world of pollution forensics. Back in the early 1990s, a conversation with his neighbor, an NCAR scientist, sparked an interest in wildfires, a major source of mercury emissions. By 1998 he had a full-time job tracking the toxin for NCAR.
With its copious mercury emissions (not only from industry but also from volcanoes, wildfires, and dust storms), Asia drew Friedli’s interest. China would never allow him to do aerial studies in its airspace, but in 2001 he heard about research flights off the coasts of Japan, Korea, and China designed to track dust particles emanating from the mainland. Friedli convinced the research team to take him along to measure mercury concentrations in the atmosphere. Throughout April 2001, 19 researchers, professors, and grad students took 16 flights aboard a cavernous retired Navy C-130 plane custom fit with 19 instruments for measuring pollutants like carbon monoxide, sulfur, and ozone.
During each flight, Friedli sat at his station awaiting readouts from his mercury sensor: an intake valve that sucked in air and guided it over a gold cartridge within the plane. Any mercury in the air would be absorbed by the gold. Every five minutes the instrument rapidly heated the gold, releasing any trapped mercury.
Plumes of mercury-laced air near the earth’s surface are mixed with other pollutants, but at 20,000 feet Friedli discovered concentrated mercury plumes soaring eastward toward North America. He concluded those plumes must have circled the entire globe at least once, releasing more ephemeral pollutants like carbon monoxide so that the mercury stood out even more.
Eager to follow the trail of Asian mercury plumes, Friedli set his sights across the Pacific, off the West Coast of the United States. In a series of 11 research flights in 2002, he identified a plume that looked very much like the ones he’d found near China the year before. Specifically, the plume had a carbon monoxide-to-mercury ratio that served as a fingerprint for gases from the same source.
What Friedli detected was just one detail of a much larger picture. Mercury plumes can wobble in latitude and altitude or park themselves in one spot for days on end. Emissions from
China—and from the United States, and indeed from every industrial country—feed a network of air currents that, as equal-opportunity polluters, serve up toxic mercury around the world.
Drawing insights from research by
Friedli and Streets, Jaffe looked at his data anew. If mercury were arriving from China, he should be able to detect it, yet his operation on Cheeka Peak showed no such signal. Conducting reconnaissance from a plane, he realized why. The peak, at 1,500 feet, hovered below the mercury plume line. Seeking a higher perch, he chose Mount Bachelor, a ski resort in central Oregon with an altitude of 9,000 feet.
In late winter 2004, Jaffe and his students huddled deep in their down jackets, bracing against a bitter gale that buffeted the chairlift ferrying them and their costly equipment to the summit. Inside the mountaintop lodge they installed a small computer lab and extended tubes outside to vacuum up the air. Later that year they conducted a similar experiment in Okinawa, Japan.
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