UC Davis researchers who just returned from a massive air-pollution study on the Pacific Rim say new Davis-made air samplers were one of the technological backbones of the project. For six weeks in April and May, six UC Davis scientists joined 124 others from 15 research institutions in the U.S., Asia and Australia, said UC Davis professor emeritus Tom Cahill. Pollution was measured from central China to Oregon and from the Arctic Circle to Hawaii by satellites, aircraft, ships and ground-based aerosol samplers. Four types of air samplers -- 60 machines in all -- designed and calibrated by UC Davis collected more than 95 percent of the samples gathered in the study for detailed analysis. "Our equipment worked flawlessly. We achieved almost all our scheduled samplings -- over 80,000 -- and the only reason we didn't get the other few percent was that some of our equipment got stuck in Chinese customs," Cahill said. Cahill and the UC Davis DELTA research group developed the samplers to help atmospheric scientists collect more detailed information, more often, about particle size, time of arrival and elemental composition. Called DRUMs, or Davis Rotating Units for Monitoring, the samplers collected pollutants at 22 sites on the ground and aboard the U.S. research vessel Ronald H. Brown. Old-style samplers collected aerosols on a single filter for 24 hours. The new UC Davis machines collect six samples every hour, yielding 144 samples daily instead of one, Cahill said. The overall research project was named ACE-Asia, for Aerosol Characterization Experiment. Its goal was to better understand the roles played by airborne particles, collectively called aerosols, in global weather, water pollution and human disease. The UC Davis DELTA Group (for Detection and Evaluation of Long-Range Transport of Aerosols) is a world leader in characterizing intercontinental transport of aerosols. Every spring, millions of tons of dust, smoke and minerals are caught up in Asian wind storms. Asia is the largest source of man-made aerosols in the world, Cahill said. Aerosols are released from coal-burning power plants and coal-fired locomotives; heavy industry, such as metals production; automobile and truck exhaust; home heating; agricultural burning; and over-tilling of dry-area farmland. They rise high in Earth's atmosphere and are deposited in and around the Pacific Ocean, from Japan to the slopes of the Rocky Mountains. The worst aerosol storms show up in California and western North America as a whitish haze in the sky. Climate modelers need to understand the role that aerosols will play in global climate change, Cahill said. Scientists believe aerosols have a major impact on climate, and at certain times and places, have more impact than better-known greenhouse gases. One key question ACE-Asia may answer is whether Asian aerosols cool the planet by scattering solar energy back into space or heat it by absorbing that energy. Cahill said this was a particularly successful expedition. "We were prepared, organized and also darn lucky. Usually, when you plan a pollution experiment, the air automatically cleans up. It's Murphy's Law. But this year was the fourth-worst dust year in Japan in 30 years. Our timing was grand." One storm in mid-April was so heavily laden, it was visible from California to the Great Lakes and triggered volcanic-ash sensors in Alaska. Now the DELTA Group offices in the College of Engineering are filling with boxed equipment and air samples returning from monitoring sites. In the next six to eight months, DELTA researchers will analyze the ACE-Asia air samples. The ACE-Asia research effort was coordinated by the University Corporation for Atmospheric Research (UCAR), a consortium of university researchers. ACE-Asia was the fifth ACE project and by far the most ambitious. The first ACE was prompted by the Kuwaiti oil fires of 1991, which showed that aerosols could have a profound effect on weather; others followed in Australia, Europe and the East Coast of the U.S.