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A particle collector on Mount Tamalpais put in place by UC Davis scientists (Photo by Steve Cliff)
A particle collector on Mount Tamalpais put in place by UC Davis scientists (Photo by Steve Cliff)

Toxic soot from China arrives at Mt. Tam


August 17, 2006

Pollutants from China have been showing up in the air above West Marin, according to recent scientific findings.

A statewide study has found Chinese pollution in the skies above California. But media reports have falsely associated the study's findings with a decrease in local air quality. While the research shows that Chinese air pollution is possibly influencing global climate change it is not impacting the air we breathe, said scientists.

Research on Mt. Tam

Since May, a research team from the University of California at Davis has collected air born particles atop Mount Tamalpais to see if Chinese pollution can be found there. The Tamalpais site has been in operation since May and is one of three across the state.

Along with the Mt. Tamalpais site, two other particle collectors are at Mount Lassen and Donner Summit near Lake Tahoe and have been collecting since February.

Particles in the free troposphere

All three sites were chosen for their altitudes, which put them above what is called the boundary layer. This part of the atmosphere, from the ground up to roughly 2000 feet, is the lowest level of the atmosphere and is where most local pollution and air particles exist. The mountains on which the collectors sit stick above the boundary layer into what is called the free troposphere. These two layers of atmosphere don't often mix. Most of the particles that pass above the California sky in the free troposphere stay there. So they are basically unadulterated in their long passage over the Pacific Ocean.

By collecting particles from the air mass that comes directly from over the largest ocean on the planet, Steve Cliff the atmospheric scientists who heads the particulate study on Mt Tamalpais hopes to gain an understanding of how particles in the air impact climate change. With accurate measurements of this air mass's particles he can get a sense of the particulate matter around the globe.

Chinese air pollution
not affecting local air quality

While there have been a series of articles in the national press about the negative impact of Chinese particle pollution on local air quality, Cliff, said that his research was misconstrued.

"We don't believe Chinese particulate air pollution is a large air quality issue at this time in the United States," said Cliff.

While pollution from Chinese industrial growth is not affecting the air that we breathe it is increasingly polluting the upper atmosphere with particulates from coal-burning power plants according to findings by the UC Davis group. The Chinese are set to build one new coal power plant every week in order to keep up with the electricity needs of their rapidly urbanizing population.

While Cliff said he is unsure about the impact of these particles on climate change until he has more data, other scientists are more certain. Some studies have even shown that in the short term particles reflect the sun's rays and help cool the earth. But other scientists counter that in the long run they will have a warming effect.

"Particles in the atmosphere from China are increasing global warming," said Thomas Cahill another atmospheric scientists out of UC Davis.

Local air pollution worse

In most cases local pollution is much more of a factor in air quality than anything coming from China.

The same is true along the coast of Marin; most particulate air pollution is created locally. While the marine layer along the coast does a good job at cleaning the air of West Marin there are still local sources of pollution, said Cort Anastasio an assistant Professors at UC Davis' Department of Land, Air and Water Resources.

According to a particulate testing station in the Point Reyes National Sea Shore, 30 percent of small particulates in the boundary layer along the coast are from ammonium sulfate and another 10 percent comes from ammonium nitrate.

While it's difficult to gauge exactly where these particles come from, Bret Schichtel a physical scientists with the Park Service which oversees 170 air testing sights nation wide, said the pollution most probably comes from off-shore shipping and inland pollution. The prevailing winds carry pollution from tanker ships' diesel engines onto the coast and periodic offshore winds blow inland pollution out though the Golden Gate along the coast. Yet all and all the majority of particulate matter in the air of West Marin is sea salt.

"The whole Northern Californian coast is quite clean," said Anastasio, about the region's air quality.

The results of the study on Mt. Tamalpais are only preliminary, said Cliff. And he plans to measure year-round particles in conjunction with the two other sites he monitors. The study on Mt. Tamalpais is located on Marin Municipal Water Distinct land and is funded by the National Oceanographic and Atmospheric Administration and the California Energy Commission.

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Last Updated on February 10, 2009