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The air up there

High altitude air quality monitoring shows global reach of air pollution
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Atmospheric scientists in recent weeks have been working atop Whistler Mountain, trying to figure out exactly what sullies the air there. It's not pollution from local cities. At 2,182 metres (7,142 feet), air collected at the huts adjacent to top lift terminal remains relatively unaffected by fumes from Vancouver, Whistler and other urban sources.

The scientists have more regional, even global ambitions. They hope to understand the influence of forest fires in California, volcanoes in Alaska and even the deserts of Asia. They have also been measuring the soot produced by proliferating coal-fired power plants, factories and highways.

"Made in China" isn't restricted to just the goods that line local stores.

The research at Whistler has been part of a broader effort in Oregon, Colorado and other states and provinces to better understand long-range transport of atmospheric pollution. This understanding matters because even as government jurisdictions in North America work to improve air quality, particles from Asia threaten to offset those gains.

"We are sitting in the perfect place to look at the chemistry," explained Allan Bertram, a researcher in atmospheric chemistry from the University of British Columbia who has been working at the lab on Whistler Mountain. "It's like a huge lab for studying chemistry."

The work at Whistler may also help partially resolve lingering uncertainty about what may be the most problematic issue of the 21 st century, global warming, also known as global climate change. Environment Canada, in cooperation with researchers from several Canadian and U.S. universities, has been studying the interactions between atmospheric particles and clouds.

So far, the formation and behavior of clouds have eluded more than a rudimentary understanding by climate scientists. The work at Whistler may help climate scientists develop computer models that better reflect how clouds heat or cool the atmosphere.

Without that understanding, climate scientists have been forced to concede that they're not absolutely sure that increasing temperatures are entirely natural or at least partially a result of human activities.

 

Asia's migratory stew

The semi-permanent laboratory atop Whistler Mountain was first established in 2002 by Environment Canada. "It is a very clean site with very little influence from North American pollution," explained the agency's Brigitte Lemay, a media relations advisor, in response to e-mailed questions.

"Because the air is very clean, trans-Pacific pollution transport events can more readily be identified and the influences quantified," she said. "At sites closer to urban sources this signal may be masked."

This transport from Asia arrives most strongly in spring, but to a lesser extent through the year. The mountain-top equipment can measure levels of ozone, carbon monoxide and mercury, but also characterize both the chemical and physical properties of atmospheric particles.

As well, scientists at Whistler and other outdoor laboratories have used technology to trace microscopic particles.

"You can distinguish between particles originating from volcanic plumes or forest fires, or dust coming from the Gobi Desert," explains Ian G. McKendry, a professor of atmospheric science at the University of British Columbia. "They all have chemical fingerprints."

Many of those fingerprints show Asia. The migratory stew includes tiny particles called aerosols that originate in the wood-burning kitchen fires of rural Chinese villages. The aerosols also come from cars and trucks now pouring onto city streets and highways, as well as the smokestacks of the smelters and coal-fired power plants built during China's binge of 13 percent annual economic growth.

The Chinese people themselves have been the primary victims of their own pollution. A 2007 World Bank report estimated 700,000 people in China die prematurely each year because of the polluted air.

Relatively little of the sullied air gets to North America. Most of it gets washed out of the atmosphere while crossing the Pacific Ocean. But a few times a year, mostly in spring, the Chinese pollution can have outsized effects when added to local pollution in North America.

Think of this trans-Pacific pollution as a shot of whiskey after a pint or two of beer. The beer alone may be tolerable. It's the shot of Chinese air on top of the local pollution that can send West Coast cities over the threshold.

 

Tracing the pollutants

Scientists have been honing their understanding of atmospheric pollution since the 1950s. Measurements taken at Hawaii's Mauna Loa Observatory first recorded the presence of dust from Asia. In time, scientists realized the dust was reaching North America, says Richard "Tony" VanCurent, an associate researcher at the University of California, Davis. One such dust storm in 1998 left cities from Los Angeles to Vancouver in a haze and perhaps a daze.

Westerly winds also carry soot and other pollutants called black carbon. A study conducted in 2004 found more than three-quarters of the black carbon over the West Coast during spring months comes from across the Pacific.

Scientists can monitor these trans-Pacific storms from images taken by orbiting satellites. A few times they have also flown into the storms to better analyze the contents. In 2007, for example, scientists boarded a specially outfitted small jet in Colorado that allowed them to fly up to 51,000 feet to study the composition of the plumes over the Pacific.

Dust particles themselves also have chemical signatures called isotopes that sometimes allow scientists to trace their origins. Studying air samples in California, soils scientist Stephanie Ewing of the U.S. Geological Survey found small particles of lead that she says clearly had originated in Asia.

The amounts are normally quite small, she explained, although larger concentrations can be detected during the spring dust storms.

 

Mt. Bachelor observations

High-mountain monitors in several locations measure pollutants borne by high-altitude wind currents. In Colorado, the Storm Peak Lab samples air atop the Steamboat ski area, 3,210 metres (10,530 feet) in elevation.

Another observatory atop Oregon's Mt. Bachelor, 2,740 metres (9,000 feet) in elevation, was established by Dan Jaffe, a professor of atmospheric and environmental chemistry at the University of Washington Bothell, after he first detected Asian pollutants arriving on the West Coast in 1997.

Like Whistler, Mt. Bachelor's monitors have helped Jaffe understand what has come from distant sources. Absent major cities nearby, "most of the time, the air atop Mt. Bachelor is the cleanest air in the United States," he says. But especially during the spring storms, monitors spike with evidence of Asian pollution. Measurements taken at Bachelor complement those taken at Whistler, he says.

Air in the West's major cities, including Los Angeles, Denver and Salt Lake City, has improved enormously in recent decades. But those gains have been offset by increasing wildfires. Studies have shown the fires generate both ground-level ozone and significant quantities of mercury.

Too, the rural West isn't quite as rural anymore. Automobile traffic has increased substantially in places like Boise or, for that matter, around Vail, Jackson Hole or other mountain resort areas where many people choose to live in large-acreage, semi-dispersed exurban locations.

In other words, Asia alone is not the problem. It's Asia in addition to local pollution. And it's Asia on particular days.

Jaffe estimates that Asia contributes only small amounts of microscopic pollutants called PM 10 and PM 2.5 on most days.

"Dust and pollution which is coming from 8,000 kilometres away will nearly always contribute less to your local air pollution than local sources," Jaffe points out.

But again, it's the occasional shot of whiskey that remains a worry. Jaffee says that on just a few days per year, as much as half of what is permitted by health standards on the West Coast arrives from across the ocean.

 

Vexing ozone problem

Most vexing to government regulators has been ground-level ozone. When found in the atmospheric layer 20 to 30 miles above the earth's surface it usefully blocks harmful ultraviolet rays.

But when at ground level, in high levels and over prolonged periods, ozone imperils breathing functions of especially young people, the elderly and anybody with respiratory diseases.

As well, it can damage high-elevation forests. Ozone causes some evergreens to lose their needles and suffer impaired ability to photosynthesize sunshine, carbon dioxide and water. Prolonged exposure can kill trees. Such damage has been documented for decades in California's ponderosa and Jeffrey pine forests, particularly in areas downwind from the Los Angeles Basin.

Created when the exhaust from cars and trucks, industrial emissions and chemical solvents are combined in the presence of sunlight, ground-level ozone was long associated with cities. In recent years, high ozone concentrations have been detected in rural areas of the Rocky Mountains, particularly in conjunction with oil-and-gas drilling.

One area of concern has been Wyoming's Upper Green River Valley, located just south of Jackson Hole. In 2008, the state's Department of Environmental Quality issued an ozone advisory after ozone levels reached 122 parts per billion volume. Another gas-drilling hot spot, the San Juan Basin of New Mexico and Colorado, has had concentrations of 95 ppbv.

The existing U.S. standard for an eight-hour average of 75 ppbv will likely be lowered again in August to somewhere between 60 and 70. The Canadian standard is already 65 parts per billion, but the method of calculating it is somewhat different.

In a 2008 appearance before the U.S.-China Economic and Security Review Commission, Jaffe said computer simulations suggest Asia pollution is responsible for just three to 10 per cent of ozone in the West on most days. On a few days each year, however, the Asian contribution is as much as 37 per cent of the federal standard.

"While this contribution is relatively modest, it will certainly increase in the future and, when added to local pollution, it can push some areas over the air-quality standard," he said.

 

Fingerprinting mercury

Mercury also poses a threat. And again, sources remain uncertain.

"We know that most of the mercury that is falling out of the atmosphere is coming from coal combustion," says Jeff Sorkin, assistant regional air program manager in Colorado for the U.S. Forest Service. But tracing mercury deposition to specific sources, even local ones, is more difficult, he says

Mercury in Colorado's San Juan Mountains illustrates the uncertainty of sources. Children and pregnant women have been warned to limit consumption of fish caught in mercury-contaminated reservoirs and lakes near the ski towns of Durango and Telluride. Circumstantial evidence has pointed toward two existing power plants in the region.

But how much mercury from Asia is ending up in the San Juan, or other mountain ranges of the West, remains unclear.

"That's the $64,000 question," says Jaffe. "That's the one everyone wants to know."

Jaffe reports that 25 to 35 percent of mercury deposition in the West comes from local or regional sources. "But that is an estimate, and that estimate depends a lot on the chemistry - which we don't fully understand," he says.

And that's why the observatory atop Whistler Mountain matters. Clear understandings of atmospheric chemistry must precede regulation. It's also needed for international cooperation.

While some analysts credit China with having become the world's leading innovator of new energy systems, it continues to plow ahead with development of conventional fossil fuels. In his 2008 testimony, Jaffe projected an increase in emissions from China of 50 to 200 percent by the year 2020 - unless China adopted advanced pollution control technologies.

 

Improving climate models

Finally, the research being conducted atop Whistler Mountain may aid climate scientists in whittling down lingering uncertainty about the human role in climate change.

"Amazingly, our poor understanding of cloud formation is responsible for the largest uncertainty in climate calculations," writes Richard A. Muller in a 2008 book titled Physics for Future Presidents. Mueller, a physicist at the University of California, Berkeley, explains that clouds are complicated, too complicated to calculate when using even the most powerful computers.

"So we resort to approximations and empirical relations from past experience. As a result, we wind up with huge uncertainties."

That, he goes on to explain, is why the International Panel on Climate Change, in its 2007 report, concluded that there is a 10 per cent chance that humans are not responsible for global warming. They can't completely rule out the potential that recent warming has absolutely nothing to do with greenhouse gases produced by burning fossil fuels.

The work at Whistler by Environment Canada and its associated university researchers may help narrow that gap of uncertainty through their study of the particles called aerosols. The aerosols can come from China, from regional forest fires, or even nearby vegetation, what is called biogenic sources.

These particles in the atmosphere can either scatter solar radiation (leading to cooling) or absorb it as well as solar radiation from the Earth (resulting in warming of the atmosphere). Particles can also alter the reflectivity and amount of clouds indirectly.

"Any assessment of the anthropogenic (human-caused) influence on climate requires quantifying the contributions of man-made particles to both the direct and indirect effect," explains Bertram. Like McKendry, his work has been funded by the Canadian Foundation for Climate and Atmospheric Science.

That's why the Whistler Mountain-top lab matters. It can deliver long-term measurements in what atmospheric scientists called the free troposphere. Planes can do the same thing, but they deliver only snapshots.

"By furthering our understanding of these different particles and their interactions with clouds, their representation in air quality and climate models can be refined and improved," explains Environment Canada.

It's unlikely that any of the work done atop Whistler Mountain will amount to break-throughs that will be reported in the 9 o'clock news. These new understandings represent progress of small steps. But, as anybody who has climbed a mountain can attest, it is the accretion of small steps that eventually leads to broader views. That's the fundamental importance of the research at Whistler this summer. It's a view that includes China and a lot of other places.

 

 



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